Tire
Content
Tire
From Wikipedia, the free encyclopedia Jump to: navigation, search This article is about tires used on road vehicles. For railroad tires, see railway tires. For other uses, see Tire (disambiguation).
Stacked and standing car tires A tire (in American English and Canadian English) or tyre (in some Commonwealth Nations such as UK, Australia and New Zealand) is a ring-shaped covering that fits around a wheel rim to protect it and enable better vehicle performance by providing a flexible cushion that absorbs shock while keeping the wheel in close contact with the ground. The word itself may be derived from the word "tie," which refers to the outer steel ring part of a wooden cart wheel that ties the wood segments together (see Etymology below). The fundamental materials of modern tires are synthetic rubber, natural rubber, fabric and wire, along with other compound chemicals. They consist of a tread and a body. The tread provides traction while the body ensures support. Before rubber was invented, the first versions of tires were simply bands of metal that fitted around wooden wheels to prevent wear and tear. Today, the vast majority of tires are pneumatic inflatable structures, comprising a doughnut-shaped body of cords and wires encased in rubber and generally filled with compressed air to form an inflatable cushion. Pneumatic tires are used on many types of vehicles, such as cars, bicycles, motorcycles, trucks, earthmovers, and aircraft.
Contents
1 Etymology and spelling 2 History 3 Manufacturing 4 Components 5 Associated components 6 Construction types
7 Specifications 8 Performance characteristics 9 Markings 10 Vehicle applications 11 Sound and vibration characteristics 12 Regulatory bodies 13 Safety 14 Asymmetric tire 15 See also 16 References 17 External links
Etymology and spelling
The Oxford English Dictionary suggests that the word derives from "attire",[1] while other sources suggest a connection with the verb "to tie".[2] From the 15th to the 17th centuries the spellings tire and tyre were used without distinction;[1] but by 1700 tyre had become obsolete and tire remained as the settled spelling.[1] In the UK, the spelling tyre was revived in the 19th century for pneumatic tires, though many continued to use tire for the iron variety. The Times newspaper in Britain was still using tire as late as 1905.[3] The 1911 edition of the Encyclopædia Britannica states that "[t]he spelling 'tyre' is not now accepted by the best English authorities, and is unrecognized in the US",[2] while Fowler's Modern English Usage of 1926 says that "there is nothing to be said for 'tyre', which is etymologically wrong, as well as needlessly divergent from our own [sc. British] older & the present American usage".[1] However, over the course of the 20th century tyre became established as the standard British spelling.
History
The earliest tires were bands of iron (later steel), placed on wooden wheels, used on carts and wagons. The tire would be heated in a forge fire, placed over the wheel and quenched, causing the metal to contract and fit tightly on the wheel. A skilled worker, known as a wheelwright, carried out this work. The outer ring served to "tie" the wheel segments together for use, providing also a wear-resistant surface to the perimeter of the wheel. The word "tire" thus emerged as a variant spelling to refer to the metal bands used to tie wheels. The first practical pneumatic tire was made by John Boyd Dunlop while working as a veterinarian in May Street, Belfast, Ireland in 1887 for his son's bicycle, in an effort to prevent the headaches his son had while riding on rough roads (Dunlop's patent was later declared invalid because of prior art by fellow Scot Robert William Thomson). Dunlop is credited with "realizing rubber could withstand the wear and tear of being a tire while retaining its resilience".[4] The development of this technology hinges on myriad engineering advances. In terms of materials, the vulcanization of natural rubber is credited to Charles Goodyear and Robert William Thomson. Synthetic rubbers were invented in the laboratories of Bayer in the
1920's.[5] Today, over 1 billion tires are produced annually in over 400 tire factories, see List of Tire Companies.
Manufacturing
Main article: Tire manufacturing Pneumatic tires are manufactured in around 450 tire factories in the world. Over 1 billion tires are manufactured annually, making the tire industry the major consumer of natural rubber. In 2015 1.72 billion tires are expected to be sold globally.[6] Tire production start with bulk raw materials such as rubber, carbon black, and chemicals and produce numerous specialized components that are assembled and cured. Many kinds of rubber are used, the most common being styrene-butadiene copolymer. This article describes the components assembled to make a tire, the various materials used, the manufacturing processes and machinery, and the overall business model.
Styrene-butadiene copolymer is the most popular material used in the production of rubber tires.[5] In 2004, $80 billion of tires were sold worldwide,[7] in 2010 it was $140 billion.[8] The top five tire manufacturing companies by revenue are Bridgestone, Michelin, Goodyear, Continental, and Pirelli.[9]
Components
A tire carcass is composed of several parts.
Tread
Main article: Tread
2 bicycle tires with different tread patterns The tread is the part of the tire that comes in contact with the road surface. The portion that is in contact with the road at a given instant in time is the contact patch. The tread is a thick rubber, or rubber/composite compound formulated to provide an appropriate level of traction that does not wear away too quickly. The tread pattern is characterized by the geometrical shape of the grooves, lugs, voids and sipes. Grooves run circumferentially around the tire, and are needed to channel away water. Lugs are that portion of the tread design that contacts the road surface. Voids are spaces between lugs that allow the lugs to flex and evacuate water. Tread patterns feature non-symmetrical (or non-uniform) lug sizes circumferentially to minimize noise levels at discrete frequencies. Sipes are valleys cut across the tire, usually perpendicular to the grooves, which allow the water from the grooves to escape to the sides in an effort to prevent hydroplaning. Treads are often designed to meet specific product marketing positions. High performance tires have small void ratios to provide more rubber in contact with the road for higher traction, but may be compounded with softer rubber that provides better traction, but wears quickly. Mud and snow (M&S) tires are designed with higher void ratios to channel away rain and mud, while providing better gripping performance. Specialized tires will always work better than general/all purpose/all weather tires when being used in the conditions the specialized tires are designed for. Tread lug Tread lugs provide the contact surface necessary to provide traction. As the tread lug enters the road contact area, or footprint, it is compressed. As it rotates through the footprint it is deformed circumferentially. As it exits the footprint, it recovers to its original shape. During the deformation and recovery cycle the tire exerts variable forces into the vehicle.[citation needed] These forces are described as Force Variation.[citation needed] Tread void Tread voids provide space for the lug to flex and deform as it enters and exits the footprint. Voids also provide channels for rainwater, mud, and snow to be channeled away from the footprint. The void ratio is the void area of the tire divided by the entire tread area. Low void areas have high contact area and therefore higher traction on clean, dry pavement. Rain groove The rain groove is a design element of the tread pattern specifically arranged to channel water away from the footprint. Rain grooves are circumferential in most truck tires. Many high performance passenger tires feature rain grooves that are angled from the center toward the sides of the tire.[citation needed] Some tire manufacturers claim that their tread pattern is designed to actively pump water out from under the tire by the action of the tread flexing.[citation needed] This results in a smoother ride in different types of weather.[citation needed]
Sipe Tread lugs often feature small narrow voids, or sipes, that improve the flexibility of the lug to deform as it traverses the footprint area. This reduces shear stress in the lug and reduces heat build up. Testing of identical siped and unsiped tires showed measurable improvements in snow traction and ice braking performance, however diminishing and extending braking distances on wet and dry pavement by a few feet on siped tires. Off-road tire enthusiasts have been siping tires for years for greater traction, as many manufacturers now offer already siped off-road-tires. Wear bar Wear bars (or wear indicators) are raised features located at the bottom of the tread grooves that indicate the tire has reached its wear limit. When the tread lugs are worn to the point that the wear bars connect across the lugs, the tires are fully worn and should be taken out of service. Most wear bars indicate a remaining tread depth of 1.6 millimetres (0.063 in) and are deemed "worn out" at that point.[10]
Bead
The bead is that part of the tire that contacts the rim on the wheel. The bead is typically reinforced with steel wire and compounded of high strength, low flexibility rubber. The bead seats tightly against the two rims on the wheel to ensure that a tubeless tire holds air without leakage. The bead fit is tight to ensure the tire does not shift circumferentially as the wheel rotates. The width of the rim in relationship to the tire is a factor in the handling characteristics of an automobile, because the rim supports the tire's profile.
Sidewall
Uneven sidewall wear, down to fabric plies, due to significant under-inflation The sidewall is that part of the tire that bridges between the tread and bead. The sidewall is largely rubber but reinforced with fabric or steel cords that provide for strength and flexibility. The sidewall transmits the torque applied by the drive axle to the tread to create traction. The sidewall, in conjunction with the air inflation, also supports the load of the vehicle. Sidewalls are molded with manufacturer-specific detail, government mandated warning labels, and other consumer information, and sometimes decorative ornamentation, like whitewalls.
Shoulder
The shoulder is that part of the tire at the edge of the tread as it makes transition to the sidewall.
Ply
Plies are layers of relatively inextensible cords embedded in the rubber[11] to hold its shape by preventing the rubber from stretching in response to the internal pressure. The orientations of the plies plays a large role in the performance of the tire and is one of the main ways that tires are categorized.
Associated components
Several additional components may be required in addition to just the tire to form a functional wheel.
Wheel
Main article: Wheel Tires are mounted onto wheels that have most often have integral rims on their outer edges to hold the tire. Automotive wheels are typically made from pressed and welded steel, or a composite of lightweight metal alloys, such as aluminum or magnesium. These alloy wheels may be either cast or forged. The mounted tire and wheel assembly is then bolted to the vehicle's hub. A decorative hubcap and trim ring may be placed over the wheel.
Rim
Main article: Rim (wheel) The beads of the tire are held on the rim, or the "outer edge" of a wheel.[12] These outer edges are shaped to obtain a proper shape on each side, having a radially cylindrical inclined inner wall on which the tire can be mounted. The wheel's rim must be of the proper design and type to hold the bead of the appropriately sized tire.[13] Tires are mounted on the wheel by forcing its beads into the channel formed by the wheel's inner and outer rims.[14]
Inner tube
Most bicycle tires, many motorcycle tires, and many tires for large vehicles such as buses, heavy trucks, and tractors are designed for use with inner tubes. Inner tubes are torus-shaped balloons made from an impermeable material, such as soft, elastic synthetic rubber, to prevent air leakage. The inner tubes are inserted into the tire and inflated to retain air pressure. Large inner tubes, which are large inflatable toruses, can be re-used for other purposes, such as swimming and rafting (see swim ring), tubing (recreation), sledding, and skitching. Purpose-built
inflatable toruses are also manufactured for these uses, offering choice of colors, fabric covering, handles, decks, and other accessories, and eliminating the protruding valve stem.
Schrader valve stem with its cap removed
Valve stem
Main article: Valve stem The valve stem is a tube made of metal or rubber, through which the tire is inflated, with a check valve, typically a Schrader valve on automobiles and most bicycle tires, or a Presta valve on high-performance bicycles. Valve stems usually protrude through the wheel for easy access. They mount directly to the rim, in the case of tubeless tires, or are an integral part of the inner tube. The rubber in valve stems eventually degrades, and, in the case of tubeless tires, replacement of the valve stem at regular intervals or with tire replacement reduces the chance of failure.
Construction types
A cross-section of a tire showing ply orientations
Bias
Bias tire (or cross ply) construction utilizes body ply cords that extend diagonally from bead to bead, usually at angles in the range of 30 to 40 degrees, with successive plies laid at opposing angles forming a crisscross pattern to which the tread is applied. The design allows the entire tire
body to flex easily, providing the main advantage of this construction, a smooth ride on rough surfaces. This cushioning characteristic also causes the major disadvantages of a bias tire: increased rolling resistance and less control and traction at higher speeds.
Belted bias
A belted bias tire starts with two or more bias-plies to which stabilizer belts are bonded directly beneath the tread. This construction provides smoother ride that is similar to the bias tire, while lessening rolling resistance because the belts increase tread stiffness. The plies and belts are at different angles, which improves performance compared to non-belted bias tires. The belts may be cord or steel.
Radial
Main article: Radial tire Radial tire construction utilizes body ply cords extending from the beads and across the tread so that the cords are laid at approximately right angles to the centerline of the tread, and parallel to each other, as well as stabilizer belts directly beneath the tread. The belts may be cord or steel. The advantages of this construction include longer tread life, better steering control, and lower rolling resistance. Disadvantages of the radial tire include a harder ride at low speeds on rough roads and in the context of off-roading, decreased "self-cleaning" ability and lower grip ability at low speeds.[15]
Solid
Many tires used in industrial and commercial applications are non-pneumatic, and are manufactured from solid rubber and plastic compounds via molding operations. Solid tires include those used for lawn mowers, skateboards, golf carts, scooters, and many types of light industrial vehicles, carts, and trailers. One of the most common applications for solid tires is for material handling equipment (forklifts). Such tires are installed by means of a hydraulic tire press.
Semi-pneumatic
Semi-pneumatic tires have a hollow center, but they are not pressurized. They are light-weight, low-cost, puncture proof, and provide cushioning.[16] These tires often come as a complete assembly with the wheel and even integral ball bearings. They are used on lawn mowers, wheelchairs, and wheelbarrows. They can also be rugged, typically used in industrial applications,[17] and are designed to not pull off their rim under use. Tires that are hollow but are not pressurized have also been designed for automotive use, such as the Tweel (a portmanteau of tire and wheel), which is an experimental tire design being developed at Michelin. The outer casing is rubber as in ordinary radial tires, but the interior has special compressible polyurethane springs to contribute to a comfortable ride. Besides the impossibility of going flat, the tires are intended to combine the comfort offered by higher-
profile tires (with tall sidewalls) with the resistance to cornering forces offered by low profile tires. They have not yet been delivered for broad market use.
Specifications
Tire pressure monitoring system
Main article: Tire pressure monitoring system Tire pressure monitoring systems (TPMS) are electronic systems that monitor the tire pressures on individual wheels on a vehicle, and alert the driver when the pressure goes below a warning limit. There are several types of designs to monitor tire pressure. Some actually measure the air pressure, and some make indirect measurements, such as gauging when the relative size of the tire changes due to lower air pressure.
Inflation pressure
Tires are specified by the vehicle manufacturer with a recommended inflation pressure, which permits safe operation within the specified load rating and vehicle loading. Most tires are stamped with a maximum pressure rating. For passenger vehicles and light trucks, the tires should be inflated to what the vehicle manufacturer recommends, which is usually located on a decal just inside the driver's door or in the vehicle owners handbook. Tires should not generally be inflated to the pressure on the sidewall; this is the maximum pressure, rather than the recommended pressure.[18] High performance and dynamic drivers often increase the tire pressure to near the maximum pressure as printed on the sidewall. This is done to sacrifice comfort for performance and safety. It is definitely very dangerous to allow tire pressure to drop below the recommended placard vehicle pressure, although this is commonly done temporarily when driving on sand to reduce chance of bogging. The reason for this is that it increases the amount of tire wall movement as a result of cornering forces. Should a low pressure tire be forced to perform an evasive maneuver, the tire wall will be more pliable than had it been of a higher pressure, and thus it will "roll" under the wheel. This increases the entire roll movement of the car, and diminishes tire contact area on the negative side of the vector. Thus only half the tire is in contact with the road, and the tire may deform to such an extent that the side wall on the positive vector side becomes in contact with the road. The probability of failing in the emergency maneuver is thus increased. Further, with low tire pressure—due to the side wall being more pliable—the tire will absorb more of the irregular forces from normal driving, and with this constant bending of the side wall as it absorbs the contours of the road, it heats up the tire wall to possibly dangerous temperatures, as well as degrades the steel wire reinforcement; this often leads to side wall blow-outs. In an extreme case of this phenomenon, the vehicle may drive into a pot-hole, or a hard elevation in the road. Due to the low tire pressure, the side wall at the contact area will temporarily collapse, thereby wedging the tire between the wheel and road, resulting in a tire laceration and blow-out, as well as a damaged wheel. High tire pressures are more inclined to keep its shape during any encounter, and will thus transmit the forces of the road to the suspension, rather than being damaged itself. This allows for an increased reaction speed, and "feel" the driver perceives of the
road. Modern tire designs allow for minimal tire contact surface deformity during high pressures, and as a result the traditional wear on the center of the tire due to reasonably high pressures is only known to very old or poorly designed tires. Feathering occurs on the junction between the tire tread and side wall, as a result of too low tire pressures. This is as a result of the inability of the tire to perform appropriately during cornering forces, leading to aberrant and shearing forces on the feathering area. This is due to the tire moving sideways underneath the wheel as the tire pressures are insufficient to transmit the forces to the wheel and suspension. It may be, that very high tire pressures have only two downsides: The sacrifice in comfort; and the increased chance of obtaining a puncture when driving over sharp objects, such as on a newly scraped gravel road. Many individuals have maintained their tire pressures at the maximum side wall printed value (inflated when cold) for the entire lifetime of the tire, with perfect wear until the end. This may be of negative economic value to the rubber and tire companies, as high tire pressures decrease wear, and minimize side wall blow outs. Many pressure gauges available at fuel stations have been de-calibrated by manhandling and the effect of time, and it is for this reason that vehicle owners should keep a personal pressure gauge with them to validate the correct tire pressure. During the early stages of tire engineering, and with current basic tires, the tire contact patch is readily reduced by both over-and-under inflation. Over-inflation may increase the wear on the center contact patch, and under-inflation will cause a concave tread, resulting in less center contact. Most modern tires will wear evenly at very high tire pressures, but will degrade prematurely due to low (or even standard) pressures. An increased tire pressure has many benefits, including decreased rolling resistance. It has been found, that an increased tire pressure almost exclusively results in shorter stopping distances, except in some circumstances that may be attributed to the low sample size.[19] If tire pressure is too low, the tire contact patch is changed more than if it were over-inflated. This increases rolling resistance, tire flexing, and friction between the road and tire. Under-inflation can lead to tire overheating, premature tread wear, and tread separation in severe cases.[20] Tires are not completely impermeable to air, and so lose pressure over time naturally. Some drivers inflate tires with nitrogen, instead of simple air, which is already 78% nitrogen, in an attempt to keep the tires at the proper inflation pressure longer,[21] though the effectiveness of this is debatable.[22][23][24]
Load rating
Tires are specified by the manufacturer with a maximum load rating. Loads exceeding the rating can result in unsafe conditions that can lead to steering instability and even rupture. For a table of load ratings, see tire code.
Speed rating
The speed rating denotes the maximum speed at which a tire is designed to be operated. For passenger vehicles these ratings range from 99 to 186 miles per hour (159 to 299 km/h). For a table of speed ratings, see tire code.
Service rating
Tires (especially in the U.S.) are often given service ratings, mainly used on bus and truck tires. Some ratings are for long haul, and some for stop-start multi-drop type work. Tires designed to run 500 miles (800 km) or more per day carrying heavy loads require special specifications.
Treadwear rating
Main article: Treadwear rating The treadwear rating or treadwear grade describes how long the tire manufacturers expect the tire to last. A Course Monitoring Tire (the standard tire that a test tire will be compared to) has a rating of "100". If a manufacturer assigns a treadwear rating of 200 to a new tire, they are indicating that they expect the new tire to have a useful lifespan that is 200% of the life of a Course Monitoring Tire. The "test tires" are all manufacturer-dependent. Brand A's rating of 500 is not necessarily going to give you the same mileage rating as Brand B's tire of the same rating. The testing is non-regulated and can vary greatly. Treadwear ratings are only useful for comparing Brand A's entire lineup against itself. Tread wear, also known as tire wear, is caused by friction between the tire and the road surface. Government legal standards prescribe the minimum allowable tread depth for safe operation.
Rotation
Tires may exhibit irregular wear patterns once installed on a vehicle and partially worn. Furthermore, front-wheel drive vehicles tend to wear the front tires at a greater rate compared to the rears. Tire rotation is the procedure of moving tires to different car positions, such as frontto-rear, in order to even out the wear, thereby extending the life of the tire. However care must be taken with unidirectional tires (tires that are designed to rotate in one direction only, for a vehicle that is going forward) so that the correct rotational direction - indicated on the side wall with an arrow-like symbol - is maintained after the swap.
Wheel alignment
Main article: Wheel alignment When mounted on the vehicle, the wheel and tire may not be perfectly aligned to the direction of travel, and therefore may exhibit irregular wear. If the discrepancy in alignment is large, then the irregular wear will become substantial if left uncorrected. Wheel alignment is the procedure for checking and correcting this condition through adjustment of camber, caster and toe angles. These settings also affect the handling characteristics of the vehicle.
Retread
Main article: Retread Tires that are fully worn can be re-manufactured to replace the worn tread. This is known as retreading or recapping, a process of buffing away the worn tread and applying a new tread.[25] Retreading is economical for truck tires because the cost of replacing the tread is less than the price of a new tire. Retreading passenger tires is less economical because the cost of retreading is high compared to the price of new cheap tires, but favorable compared to high-end brands. Worn tires can be retreaded by two methods, the mold or hot cure method and the pre-cure or cold one. The mold cure method involves the application of raw rubber on the previously buffed and prepared casing, which is later cured in matrices. During the curing period, vulcanization takes place and the raw rubber bonds to the casing, taking the tread shape of the matrix. On the other hand, the pre-cure method involves the application of a ready-made tread band on the buffed and prepared casing, which later is cured in an autoclave so that vulcanization can occur. During the retreading process, retread technicians must ensure the casing is in the best condition possible to minimize the possibility of a casing failure. Casings with problems such as capped tread, tread separation, unrepairable cuts, corroded belts or sidewall damage, or any run-flat or skidded tires, will be rejected. In most situations, retread tires can be driven under the same conditions and at the same speeds as new tires with no loss in safety or comfort.[26] The percentage of retread failures should be about the same as for new tire failures, but many drivers, including truckers, are guilty of not maintaining proper air pressure on a regular basis, and, if a tire is abused (overloaded, underinflated, or mismatched to the other tire on a set of duals), then that tire (new or recapped) will fail.[27] Many commercial trucking companies put retreads only on trailers, using only new tires on their steering and drive wheels. This procedure increases the driver's chance of maintaining control in case of problems with a retreaded tire.
Performance characteristics
The interaction of a tire with the pavement is a very complex phenomenon. Many of the details are modeled in Pacejka's Magic Formula. Some are explained below.
Balance
Main article: Tire balance When a wheel and tire rotate, they exert a centrifugal force on the axle that depends on the location of their center of mass and the orientation of their moment of inertia. This is referred to as balance, imbalance, or unbalance. Tires are checked at the point of manufacture for excessive static imbalance and dynamic imbalance using automatic tire balance machines. Tires are
checked again in the auto assembly plant or tire retail shop after mounting the tire to the wheel. Assemblies that exhibit excessive imbalance are corrected by applying balance weights to the wheels to counteract the tire/wheel imbalance. To facilitate proper balancing, most high performance tire manufacturers place red and yellow marks on the sidewalls to enable the best possible match-mounting of the tire/wheel assembly. There are two methods of match-mounting high performance tire to wheel assemblies using these red (uniformity) or yellow (weight) marks.[28]
Camber thrust
Main article: Camber thrust Camber thrust and camber force are terms used to describe the force generated perpendicular to the direction of travel of a rolling tire due to its Camber angle and finite contact patch.
Centrifugal growth
A tire rotating at higher speeds tends to develop a larger diameter, due to centrifugal forces that force the tread rubber away from the axis of rotation. This may cause speedometer error. As the tire diameter grows, the tire width decreases. This centrifugal growth can cause rubbing of the tire against the vehicle at high speeds. Motorcycle tires are often designed with reinforcements aimed at minimizing centrifugal growth.[citation needed]
Circle of forces
Main article: Circle of forces The circle of forces, traction circle, friction circle, or friction ellipse is a useful way to think about the dynamic interaction between a vehicle's tire and the road surface.
Contact patch
Main article: contact patch The contact patch, or footprint, of the tire, is the area of the tread that is in contact with the road surface. This area transmits forces between the tire and the road via friction. The length-to-width ratio of the contact patch affects steering and cornering behavior.
Cornering force
Main article: Cornering force Cornering force or side force is the lateral (i.e. parallel to the road surface) force produced by a vehicle tire during cornering.
Dry traction
Dry traction is measure of the tire's ability to deliver traction, or grip, under dry conditions. Dry traction is a function of the tackiness of the rubber compound.
Force variation
The tire tread and sidewall elements undergo deformation and recovery as they enter and exit the footprint. Since the rubber is elastomeric, it is deformed during this cycle. As the rubber deforms and recovers, it imparts cyclical forces into the vehicle. These variations are collectively referred to as tire uniformity. Tire uniformity is characterized by radial force variation (RFV), lateral force variation (LFV) and tangential force variation. Radial and lateral force variation is measured on a force variation machine at the end of the manufacturing process. Tires outside the specified limits for RFV and LFV are rejected. Geometric parameters, including radial runout, lateral runout, and sidewall bulge, are measured using a tire uniformity machine at the tire factory at the end of the manufacturing process as a quality check. In the late 1990s, Hunter Engineering introduced the GSP9700 Road Force balancer, which is equipped with a load roller similar to the force variation machine used at the factory to grade tire uniformity. This machine can find the best position for the tire on a given wheel so that the over-all assembly is as round as possible.
Load sensitivity
Main article: Tire load sensitivity Load sensitivity is the behaviour of tires under load. Conventional pneumatic tires do not behave as classical friction theory would suggest. Namely, the load sensitivity of most real tires in their typical operating range is such that the coefficient of friction decreases as the vertical load, Fz, increases.
Pneumatic trail
Main article: Pneumatic trail Pneumatic trail of a tire is the trail-like effect generated by compliant tires rolling on a hard surface and subject to side loads, as in a turn. More technically, it is the distance that the resultant force of side-slip occurs behind the geometric center of the contact patch.
Relaxation length
Main article: Relaxation length Relaxation length is the delay between when a slip angle is introduced and when the cornering force reaches its steady-state value.
Rolling resistance
Main article: Rolling resistance Rolling resistance is the resistance to rolling caused by deformation of the tire in contact with the road surface. As the tire rolls, tread enters the contact area and is deformed flat to conform to the roadway. The energy required to make the deformation depends on the inflation pressure, rotating speed, and numerous physical properties of the tire structure, such as spring force and stiffness. Tire makers seek lower rolling resistance tire constructions to improve fuel economy in cars and especially trucks, where rolling resistance accounts for a high proportion of fuel consumption. Pneumatic tires also have a much lower rolling resistance than solid tires. Because the internal air pressure acts in all directions, a pneumatic tire is able to "absorb" bumps in the road as it rolls over them without experiencing a reaction force opposite to the direction of travel, as is the case with a solid (or foam-filled) tire. The difference between the rolling resistance of a pneumatic and solid tire is easily felt when propelling wheelchairs or baby buggies fitted with either type so long as the terrain has a significant roughness in relation to the wheel diameter.[citation needed]
Self aligning torque
Main article: Self aligning torque Self aligning torque, also known as the aligning torque, SAT or Mz, is the torque that a tire creates as it rolls along that tends to steer it, i.e. rotate it around its vertical axis.
Slip angle
Main article: Slip angle Slip angle or sideslip angle is the angle between a rolling wheel's actual direction of travel and the direction towards which it is pointing (i.e., the angle of the vector sum of wheel translational velocity and sideslip velocity ).
Stopping distance
Performance-oriented tires have a tread pattern and rubber compounds designed to grip the road surface, and so usually have a slightly shorter stopping distance. However, specific braking tests are necessary for data beyond generalizations.
Work load
The work load of a tire is monitored so that it is not put under undue stress, which may lead to its premature failure.[29] Work load is measured in ton kilometre per hour (TKPH). The measurement's appellation and units are the same. The recent shortage and increasing cost of tires for heavy equipment has made TKPH an important parameter in tire selection and equipment maintenance for the mining industry. For this reason, manufacturers of tires for large earth-moving and mining vehicles assign TKPH ratings to their tires based on their size,
construction, tread type, and rubber compound.[30][31] The rating is based on the weight and speed that the tire can handle without overheating and causing it to deteriorate prematurely. The equivalent measure used in the United States is ton mile per hour (TMPH).
Tread wear
There are several types of abnormal tread wear. Poor wheel alignment can cause excessive wear of the innermost or outermost ribs. Gravel roads, rocky terrain, and other rough terrain causes accelerated wear. Over-inflation above the sidewall maximum can cause excessive wear to the center of the tread. Modern tires have steel belts built in to prevent this. Under-inflation causes excessive wear to the outer ribs. Often, the placard pressure is too low and most tires are underinflated as a result.[citation needed] Unbalanced wheels can cause uneven tire wear, as the rotation may not be perfectly circular. Tire manufacturers and car companies have mutually established standards for tread wear testing that include measurement parameters for tread loss profile, lug count, and heel-toe wear. See also Work load above.
Wet traction
Wet traction is the tire's traction, or grip, under wet conditions. Wet traction is improved by the tread design's ability to channel water out of the tire footprint and reduce hydroplaning. However, tires with a circular cross-section, such as those found on racing bicycles, when properly inflated have a sufficiently small footprint to not be susceptible to hydroplaning. For such tires, it is observed that fully slick tires will give superior traction on both wet and dry pavement.[32]
Markings
DOT code
In the United States, the DOT Code is an alphanumeric character sequence molded into the sidewall of the tire for purposes of tire identification. The DOT Code is mandated by the U.S. Department of Transportation. The DOT Code is useful in identifying tires in a product recall. The DOT Code begins with the letters "DOT" followed by a plant code (two numbers or letters) that identifies where it was manufactured. The last four numbers represent the week and year the tire was built. A three-digit code was used for tires manufactured before 2000. For example, 178 means it was manufactured in the 17th week of 8th year of the decade. In this case it means 1988. For tires manufactured in the 1990s, the same code holds true, but there is a little triangle (Δ) after the DOT code. Thus, a tire manufactured in the 17th week of 1998 would have the code 178Δ. In 2000, the code was switched to a 4-digit code. Same rules apply, so for example, 3003 means the tire was manufactured in the 30th week of 2003. Other numbers are marketing codes used at the manufacturer's discretion.
E-mark
All tires sold for road use in Europe after July 1997 must carry an E-mark. The mark itself is either an upper case "E" or lower case "e" – followed by a number in a circle or rectangle, followed by a further number. An (upper case) "E" indicates that the tire is certified to comply with the dimensional, performance and marking requirements of ECE regulation 30. A (lower case) "e" indicates that the tire is certified to comply with the dimensional, performance and marking requirements of Directive 92/23/EEC. The number in the circle or rectangle denotes the country code of the government that granted the type approval. The last number outside the circle or rectangle is the number of the type approval certificate issued for that particular tire size and type.
Mold serial number
Tire manufacturers usually embed a mold serial number into the sidewall area of the mold, so that the tire, once molded, can be traced back to the mold of original manufacturer.
Codes
Main article: Tire code
Vehicle applications
Tires are classified into several standard types, based on the type of vehicle they serve. Since the manufacturing process, raw materials, and equipment vary according to the tire type, it is common for tire factories to specialize in one or more tire types. In most markets, factories that manufacture passenger and light truck radial tires are separate and distinct from those that make aircraft or off-the-road (OTR) tires.[citation needed]
Passenger vehicles and light truck
High performance High performance tires are designed for use at higher speeds, and more often, a more "sporty" driving style. They feature a softer rubber compound for improved traction, especially on high speed cornering. The trade off of this softer rubber is shorter tread life. High performance street tires sometimes sacrifice wet weather handling by having shallower water channels to provide more actual rubber tread surface area for dry weather performance.[citation needed] The ability to provide a high level of performance on both wet and dry pavement varies widely among manufacturers, and even among tire models of the same manufacturer. This is an area of active research and development, as well as marketing. Mud and snow Main article: Snow tires
The examples and perspective in this section may not represent a worldwide view of the subject. Please improve this article and discuss the issue on the talk page. (July 2010) Mud and Snow, (or M+S, or M&S), is a designation applied rather arbitrarily by manufacturers for all-season and winter tires designed to provide improved performance under low temperature conditions, compared to summer tires. The tread compound is usually softer than that used in tires for summer conditions, thus providing better grip on ice and snow, but wears more quickly at higher temperatures. Tires may have well above average numbers of sipes in the tread pattern to grip the ice. There are no traction performance requirements which such a tire has to meet; M&S relates to the percentage of tread void area. Dedicated winter tires will bear the "Mountain/Snowflake Pictograph" if designated as a winter/snow tire by the American Society for Testing & Materials. Winter tires will typically also carry the designation MS, M&S, or the words MUD AND SNOW (but see All-season tires, below).
Studded, highly siped, winter tire Some winter tires may be designed to accept the installation of metal studs for additional traction on icy roads. The studs also roughen the ice, thus providing better friction between the ice and the soft rubber in winter tires. Use of studs is restricted in most countries with the notable exception of the Nordic countries where they are commonly used during the winter season outside metropolitan areas, and even prohibited in some locales due to the increased road wear caused by studs. Typically, studs are never used on heavier vehicles, except ice resurfacers. The upper tier classes of ice racing[33] and rallying mandates the vehicles be equipped with studded tires. Other winter tires rely on factors other than studding for traction on ice, e.g. highly porous or hydrophilic rubber that adheres to the wet film on the ice surface. Some jurisdictions may require snow tires or tire chains on vehicles driven in certain areas during extreme weather conditions.
Mud tires are speciality tires with large, chunky tread patterns designed to bite into muddy surfaces. The large, open design also allows mud to clear quickly from between the lugs. Mud terrain tires also tend to be wider than other tires, to spread the weight of the vehicle over a greater area to prevent the vehicle from sinking too deeply into the mud. However in reasonable amounts of mud and snow, tires should be thinner. Being thinner, the tire will have more pressure on the road surface, thus allowing the tires to penetrate the snow layer and grip harder snow or road surface beneath. This does not compensate when the snow is too deep for such penetration, where the vehicle will sink into the snow and plough the snow in front and eventually pack it beneath it until the wheels no longer have traction. In this case, wider tires are preferred, as they have a larger contact patch and are better able to 'float' on top of the mud or snow. All season The All Season tire classification is a compromise between one developed for use on dry and wet roads during summer and one developed for use under winter conditions. The type of rubber and the tread pattern best suited for use under summer conditions cannot, for technical reasons, give good performance on snow and ice. The all-season tire is a compromise, and is neither an excellent summer tire nor an excellent winter tire. They have, however, become ubiquitous as original and replacement equipment on automobiles marketed in the United States, due to their convenience and their adequate performance in most situations. Even so, in other parts of the world, like Germany, it is common to have a designated tire set for winter and summer. AllSeason tires are also marked for mud and snow the same as winter tires but rarely with a snowflake. Owing to the compromise with performance during summer, winter performance is usually poorer than a winter tire. All-terrain All-terrain tires are typically used on SUVs and light trucks. These tires often have stiffer sidewalls for greater resistance against puncture when traveling off-road, the tread pattern offers wider spacing than all-season tires to remove mud from the tread. Many tires in the all-terrain category are designed primarily for on-road use, particularly all-terrain tires that are originally sold with the vehicle. Spare Main article: spare tire Some vehicles carry a spare tire, already mounted on a wheel, to be used in the event of flat tire or blowout. Minispare, or "space-saver spare" tires are smaller than normal tires to save on trunk/boot space, gas mileage, weight, and cost. Minispares have a short life expectancy and a low speed rating, often below 60 miles per hour (97 km/h). Run-flat Main article: Run-flat tire
Several innovative designs have been introduced that permit tires to run safely with no air for a limited range at a limited speed. These tires typically feature strong, load-supporting sidewalls. An infamous example of an alternate run-flat technology has plastic load-bearing inserts attached to the rim instead of the reinforced sidewalls. A disadvantage is that run-flat tires cannot be repaired if a puncture occurs, this is due to manufacturer's informing the automotive industry that you cannot tell what kind of state the sidewall is in due to the compacted sidewall of rubber.
Heavy duty truck
Heavy load may require multiple tires Heavy duty tires are also referred to as Truck/Bus tires. These are the tire sizes used on vehicles such as commercial freight trucks, dump trucks, and passenger buses. Truck tires are subcategorized into specialties according to vehicle position such as steering, drive axle, and trailer. Each type is designed with the reinforcements, material compounds, and tread patterns that best optimize the tire performance. A relatively new concept is the use of "Super Singles" or Wide Singles. Generally in a dual configuration, there are 2 tires per position, each between 275 mm295 mm wide. The Super Single replaces these with a single tire, usually 455 mm wide. This allows for less tread to be contacting the ground and also eliminates 2 sidewalls per position. Along with the weight savings of about 91 kilograms (200 lb) per axle, this enables vehicles using these to improve fuel economy.
Off-the-road
Off-the-road (OTR) tires being transported Off-the-road (OTR) tires include tires for construction vehicles such as wheel loaders, backhoes, graders, trenchers, and the like; as well as large mining trucks. OTR tires can be of either bias or radial construction although the industry is trending toward increasing use of radial. Bias OTR tires are built with a large number of reinforcing plies to withstand severe service conditions and high loads. Dramatically increasing commodity prices has led to shortages of new tires. As a consequence, multi-million dollar trucks can be idled for lack of tires, costing mines millions of dollars in lost productivity. This has led to a stronger effort to recycle old OTR tires. As of 2008, a new OTR tire can cost up to $50,000; retread tires are sold at half the price of new tires, and last 80% as long.[34] Retreading an OTR tire is labor intensive. First, the retreading technician must place the old tire in a buffing machine to remove what remains of the old tread; "skiving" follows this, which is the removal, by hand, of material the buffing misses. Next, the technician must inspect the tire, repairing defects. Lastly, the technician fills holes in the tire with rubber, applies a cement gum adhesive, and places the tire on a machine that will apply a new tread.[35]
Agricultural
The agricultural tire classification includes tires used on farm vehicles, typically tractors and specialty vehicles like harvesters. Driven wheels have very deep, widely spaced lugs to allow the tire to grip soil easily. High flotation tires are used in swampy environments and where soil compaction is a concern, featuring large footprints at low inflation pressures.
Racing
NASCAR tires Racing tires are highly specialized according to vehicle and race track conditions. This classification includes tires for drag racing, Auto-x, drifting, Time Attack, Road Racing – as well as the large-market race tires for Formula One, IndyCar, NASCAR, rallying, MotoGP and the like. Tires are specially engineered for specific race tracks according to surface conditions, cornering loads, and track temperature. Racing tires often are engineered to minimum weight targets, so tires for a 500 miles (800 km) race may run only 100 miles (160 km) before a tire change. Some tire makers invest heavily in race tire development as part of the company's marketing strategy and a means of advertising to attract customers. Racing tires often are not legal for normal highway use.
Industrial
Airless tire The Industrial tire classification is a bit of a catch-all category and includes pneumatic and nonpneumatic tires for specialty industrial and construction equipment such as skid loaders and fork lift trucks.
Bicycle
Main article: Bicycle tire
A bicycle tire in the style of a cruiser This classification includes all forms of bicycle tires, including road racing tires, mountain bike tires, snow tires, and tubular tires, used also with other human-powered vehicles (see Category:Human-powered vehicles).
Aircraft
Changing a tire on a P-3C Orion aircraft Aircraft tires are designed to withstand extremely heavy loads for short durations. The number of tires required for aircraft increases with the weight of the plane (because the weight of the airplane has to be distributed better). Aircraft tire tread patterns are designed to facilitate stability in high crosswind conditions, to channel water away to prevent hydroplaning, and for braking effect. Aircraft tires are usually inflated with nitrogen or helium to minimize expansion and contraction from extreme changes in ambient temperature and pressure experienced during flight.[citation needed] Dry nitrogen expands at the same rate as other dry atmospheric gases, but common compressed air sources may contain moisture, which increases the expansion rate with temperature.[citation needed] Aircraft tires generally operate at high pressures, up to 200 pounds per square inch (14 bar; 1,400 kPa) for airliners, and even higher for business jets. Tests of airline aircraft tires have shown that they are able to sustain pressures of maximum 800 pounds per square inch (55 bar; 5,500 kPa) before bursting. During the test the tires have to be filled with water, instead of helium or nitrogen, which is the common content of aircraft tires, to prevent the test room being blown apart by the energy when the tire bursts.
Aircraft tires also include heat fuses, designed to melt at a certain temperature. Tires often overheat if maximum braking is applied during an aborted takeoff or an emergency landing. The fuses provide a safer failure mode that prevents tire explosions by deflating in a controlled manner, thus minimizing damage to aircraft and objects in the surrounding environment. The requirement that an inert gas, such as nitrogen, be used instead of air for inflation of tires on certain transport category airplanes was prompted by at least three cases in which the oxygen in air-filled tires combined with volatile gases given off by a severely overheated tire and exploded upon reaching autoignition temperature. The use of an inert gas for tire inflation will eliminate the possibility of a tire explosion.[36]
Motorcycle
Main article: Motorcycle tyre There are many different types of motorcycle tires: This section's factual accuracy is disputed. (April 2008) Sport Touring – these tires are generally not used for high cornering loads, but for long straights, good for riding across the country. Sport Street – these tires are for aggressive street riders that spend most of their time carving corners on public roadways. These tires do not have a long life, but in turn have better traction in high speed cornering. Street and sport street tires have good traction even when cold, but when warmed too much, can actually lose traction as their internal temperature increases. Track or Slick – these tires are for track days or races. They have more of a triangular form, which in turn gives a larger contact patch while leaned over. These tires are not recommended for the street by manufacturers, and are known to have a shorter life on the street. Due to the triangulation of the tire, there will be less contact patch in the center, causing the tire to develop a flat spot quicker when used to ride on straightaways for long periods of time and have no tread so they lose almost all grip in wet conditions. Racing slicks are also made of a harder rubber compound and do not provide as much traction as street tires until warmed to a higher internal temperature than street tires normally operate at. Most street riding will not put a sufficient amount of friction on the tire to maintain the optimal tire temperature, especially in colder climates and in spring and fall.
Sound and vibration characteristics
Main article: Roadway noise The design of treads and the interaction of specific tire types with the roadway surface type produces considerable effect upon sound levels or noise pollution emanating from moving vehicles. These sound intensities increase with higher vehicle speeds.[37] The acoustic intensity
produced varies considerably depending on the tire tread design and the road surface type. There is a study "under development" that aims predict the interior noise due to the vibrations of a rolling tire structurally transmitted to the hub of a vehicle".[38]
Regulatory bodies
DOT
The United States Department of Transportation (DOT) is the U.S. governmental body authorized by the U.S. Congress to establish and regulate transportation safety in the United States of America.
NHTSA
The National Highway and Traffic Safety Administration (NHTSA) is a U.S. government body within the Department of Transportation tasked with regulating automotive safety in the United States.
UTQG
The Uniform Tire Quality Grading System (UTQG), is a system for comparing the performance of tires, established by the United States National Highway Traffic Safety Administration according to the Code of Federal Regulations 49 CFR 575.104. The UTQG regulation requires labeling of tires for tread wear, traction, and temperature.
T&RA
The Tire and Rim Association (T&RA) is a voluntary U.S. standards organization to promote the interchangeability of tires and rim and allied parts. Of particular interest, they published key tire dimension standards, key rim contour dimension standards, key tire valve dimension standards, and load / inflation standards.
ETRTO
The European Tyre and Rim Technical Organization (ETRTO) is the European standards organization "to establish engineering dimensions, load/pressure characteristics and operating guidelines" .[39] for tires, rims and valves. It is analogous to T&RA.
JATMA
The Japanese Automobile Tire Manufacturers Association (JATMA) is the Japanese standards organization for tires, rims and valves. It is analogous to T&RA and ETRTO.
TREAD Act
The Transportation Recall Enhancement, Accountability and Documentation Act (TREAD Act) is a United States federal law that sets standards for testing and the reporting of information related to products involved with transportation such as cars and tires.
RFID tags
Radio Frequency IDentification tags (RFID) are passive transponders affixed to the inside of the tire for purposes of automatic identification.[citation needed] Tags are encoded with various types of manufacturing data, including the manufacturer's name, location of manufacture, tire type, manufacturing date, and in some cases test data. RFID transponders can remotely read this data automatically. RFID tags are used by auto assemblers to identify tires at the point of assembly to the vehicle.[citation needed] Fleet operators utilize RFID as part of tire maintenance operations. CCC (China Compulsory Certification) is a mandatory certification system concerning product safety in China that went into effect in August 2002. Before CCC, there were two certification systems in China: CCIB and CCEE. With China's entrance into the WTO, these two systems were unified into the CCC certification system. After the termination of a one-year grace period in August 2003, the system became compulsory.The CCC certification system is operated by the State General Administration for Quality Supervision and Inspection and Quarantine of the People's Republic of China (AQSIQ) and the Certification and Accreditation Administration of the People's Republic of China (CNCA).
Safety
Proper vehicle safety requires specific attention to inflation pressure, tread depth, and general condition of the tires. Over-inflated tires run the risk of explosive decompression (they may pop). On the other hand, under-inflated tires have a higher rolling resistance and suffer from overheating and rapid tread wear particularly on the edges of the tread. Excessive tire wear will reduce steering and braking response,[citation needed] and tires worn down past their safety margins and into the casing run the very real risk of rupturing. Also, certain combinations of cross ply and radial tires on different wheels of the same vehicle can lead to vehicle instability, and may also be illegal. Vehicle and tire manufacturers provide owners' manuals with instructions on how to check and maintain tires.
Flat
Main article: Flat tire
A flat tire A flat tire occurs when a tire deflates. This can occur as a result of normal wear-and-tear, a leak, or more serious damage. A tire that has lost sufficient pressure will impair the stability of the vehicle and may damage the tire further if it is driven in this condition. The tire should be changed and/or repaired before it becomes completely flat. Continuing to drive a vehicle with a flat tire will damage the tire beyond repair, possibly damage the rim and vehicle, and put the occupants and other vehicles in danger. A flat tire or low-pressure tire should be considered an emergency situation, requiring immediate attention. Some tires, known as "run-flat tires", have either extremely stiff sidewalls or a resilient filler to allow driving a limited distance while flat, usually at reduced speed, without permanent damage or hazard. A modern radial tire may not be visibly distorted even with dangerously low inflation pressure. (This is especially true of tires with a low aspect ratio, sometimes known as "low profile" tires.) Thus maintenance of adequate tire pressure can have important safety implications despite the fact that most car owners neglect it. Tire designers have tried to make new tires fail-safe so that the failure of the operator to maintain the tire pressure won't cause a major safety concern, but there are limitations on this.
Hydroplaning (or aquaplaning)
Main article: Hydroplaning (road vehicle) Hydroplaning, also known as aquaplaning, is the condition where a layer of water builds up between the tire and road surface. Hydroplaning occurs when the tread pattern cannot channel away enough water at an adequate rate to ensure a semi-dry footprint area. When hydroplaning occurs, the tire effectively "floats" above the road surface on a cushion of water – and loses traction, braking and steering, creating a very unsafe driving condition. When hydroplaning occurs, there is considerably less responsiveness of the steering wheel. The correction of this unsafe condition is to gradually reduce speed, by merely lifting off the accelerator/gas pedal. Hydroplaning becomes more prevalent with wider tires (because of the lower weight per contact area) and especially at higher speeds; it is of virtually no concern to bicycle tires under normal riding conditions largely because of the lower speeds. The chance of car hydroplaning is also minimal at bicycle speeds as the weight per contact area of car tires is not much lower if any than bicycle tires.
Dangers of aged tires
Research and tests show that as tires age, they begin to dry out and become potentially dangerous, even if unused. Aged tires may appear to have similar properties to newly manufactured tires, but rubber degrades over time, and once the vehicle is traveling at high speeds (i.e. on a freeway) the tread could peel off, leading to severe loss of control. In tropical climates, such as Singapore, tires degrade sooner than in temperate climates, and more care should be taken in these climates to ensure that tires do not fail.[citation needed] Also, tires on
seldom-used trailers are at the greatest risk of age-failure, but some tires are built to withstand idleness, usually with nylon reinforcement. Many automakers recommend replacing tires after six years, and several tire manufacturers (Bridgestone, Michelin) have called for tires to be removed from service 10 years after the date of manufacture. However, an investigative report by Brian Ross on ABC's 20/20 news magazine found that many major retailers such as Goodyear, Wal-Mart, and Sears were selling tires that had been produced six or more years ago. Currently, no law for aged tires exists in the United States.[40][41]
Scrap tires and environmental issues
A child plays in a playground made from recycled tires. Guelph, Canada Once tires are discarded, they are considered scrap tires. Scrap tires are often re-used for things from bumper car barriers to weights to hold down tarps. Some facilities are permitted to recycle scrap tires through chipping, and processing into new products, or selling the material to licensed power plants for fuel. Some tires may also be retreaded for re-use. One group did "a study to evaluate the possibility of using scrap tires as a crash cushion system. The objective of this study was to evaluate the material properties of used tires and recycled tire-derived materials for use in low-cost, reusable crash cushions".[42] An interesting use, developed over 30 years back but not yet universally used, is to process scrap tires as raw material for roads. The process is removing the metal, granulating the rubber and then a chemical process where it is mixed with other usual materials for macadamised roads. The resulting roads have proved to have better waterproofing, more resilent resulting in a smoother ride and also longer tire life. Several countries (for example, South Korea) have regulations requiring its use, but most do not. Americans generate about 285 million scrap tires per year.[43] Many states have regulations as to the number of scrap tires that you may have on site, due to concerns with dumping, fire hazards, and mosquitoes. In the past, millions of tires have been discarded into open fields. This creates a breeding ground for mosquitoes, since the tires often hold water inside and remain warm enough for mosquito breeding. Mosquitoes create a nuisance and may increase the likelihood of spreading disease. It also creates a fire danger, since such a large tire pile is a lot of fuel. Some tire fires have burned for months, since water does not adequately penetrate or cool the burning tires. Tires have been known to liquefy, releasing hydrocarbons and other contaminants to the
ground and even ground water, under extreme heat and temperatures from a fire. The black smoke from a tire fire causes air pollution and is a hazard to down wind properties. The use of scrap tire chips for landscaping has become controversial, due to the leaching of metals and other contaminants from the tire pieces. Zinc is concentrated (up to 2% by weight) to levels high enough to be highly toxic to aquatic life and plants.[44] Of particular concern is evidence that some of the compounds that leach from tires into water, contain hormone disruptors and cause liver lesions.[45]
Asymmetric tire
An asymmetric tire is a term used to describe some specific stabilization methods used in cars.
Tire tread
An asymmetric tire may refer to a tire whose tread pattern does not form in line symmetry or point symmetry vis-à-vis its central line, thus having a distinct inside and outside edge. They may be mounted on either side of the vehicle. Since the tread pattern of many ordinary tires do not form symmetry in relation to design or pattern noise, the method of mounting tires is specially prescribed. This type of tires is used in many cases to promote tire performance, braking performance, and turning performance, since tread contact changes according to the change in alignment during travel. Tires may also be directional, where the tread pattern favors operation in one direction. This usually takes the form of v-shaped grooves that help to disperse water from the center to the edge of the tread. Symmetric directional tires can be used on both sides, but once mounted on a rim cannot be moved to the other side, since the tread pattern will be in the wrong direction. This restricts tire rotation. Some directional tires are also asymmetric, in which case there will be specific left and right-handed versions.
Stabilizing belts
An asymmetric tire may refer to a passenger car radial tire in which asymmetric structure stabilizing belts are built. Generally the stabilizing belts give a self-aligning torque when a motor vehicle is running straight ahead as well as when it is cornering. However, the sidewalls of the radial tire are so flexible that there will be a delay in the lateral reaction between the tread of the tire and the rim of its wheel as the vehicle is being steered positively. The lateral force will be transmitted from the front wheel to the rear of the vehicle, which will tend to be steered off course. Whereas the asymmetric belts bring a gradual change in the lateral displacement of the tire tread corresponding to the rim while the cornering load grows. The progressive change will harden the sidewalls to produce an immediate response to steering, which results in safer driving.
See also
Camber thrust
Ground pressure
Tire-pressure gauge
Central Tire Inflation System Cornering force Direct tire pressure monitoring system Dry steering Groove wander
Low-rolling resistance tires Pneumatic trail Relaxation length Skid mark Slip (vehicle dynamics)
Tire-pressure monitoring system Tire label Tire recycling Tramlining
References
1. ^ a b c d Fowler, H. W.; David Crystal (ed.) (2009). A Dictionary of Modern English Usage: The Classic First Edition. Oxford University Press. p. 655. ISBN 978-0-19953534-7. Retrieved 2010-10-23. 2. ^ a b Chisholm, Hugh, ed. (1911). Encyclopædia Britannica, vol. 26. Encyclopædia Britannica. p. 1007. 3. ^ Peters, Pam (2004). The Cambridge Guide to English Usage. Cambridge University Press. p. 553. ISBN 978-0-521-62181-6. 4. ^ Dunlop, John Boyd (2008). Hutchinson Dictionary of Scientific Biography. AccessScience. Retrieved 9 July 2009. 5. ^ a b Werner Obrecht, Jean-Pierre Lambert, Michael Happ, Christiane Oppenheimer-Stix, John Dunn and Ralf Krüger "Rubber, 4. Emulsion Rubbers" in Ullmann's Encyclopedia of Industrial Chemistry, 2012, Wiley-VCH, Weinheim. doi:10.1002/14356007.o23_o01 6. ^ Global Tire Shipments to Reach 1.7 Billion Units by 2015, According to a New Report by Global Industry Analysts, Inc 7. ^ Global tire industry hits $80 billion. | Goliath Business News 8. ^ [1][dead link] 9. ^ Research Report on World's Top 50 Tire Enterprises, 2010-2011 Market Research Report - 02 December 2010 10. ^ KwikFit. "How can I tell when my tyres need changing?". Retrieved 2010-10-23. 11. ^ Jazar, Reza N. (2008). Vehicle dynamics: theory and applications. Springer. p. 11. ISBN 978-0-387-74243-4. Retrieved 2011-03-16. "Inner layers are made of different fabrics, called plies." 12. ^ Jewel, Elizabeth, ed. (2006). The Pocket Oxford Dictionary and Thesaurus. Oxford University Press. p. 722. ISBN 978-0-19-530715-3. Retrieved 2012-03-14. 13. ^ "Demounting and Mounting Procedures". Occupational Safety and Health Administration. 2011. Retrieved 2012-03-14. 14. ^ American Machinist, Volume 40. 1914-04-02. pp. 597–598. Retrieved 2012-03-14. 15. ^ "Bias vs Radial Tires". Mud-throwers.com. Retrieved 2010-10-23. 16. ^ Jones, Thomas H. (1980). "Get things moving with casters, glides, and wheels". Popular Science 216 (5): 148. ISSN 0161-7370. 17. ^ "Thomas Net sources for industrial use 'Semi-Pneumatic Wheels'". Thomasnet.com. Retrieved 2010-10-23. 18. ^ "Car Talk Service Advice: Tire Pressure". Retrieved 2009-01-16. 19. ^ "FEA Chapter III: Tire pressure survey and test results". Retrieved 2009-01-16. 20. ^ "NHTSA test". Retrieved 2009-01-16.
21. ^ Lydall, Ross (2010-05-21). "Taking a ride on Boris's hot wheels hire bikes". London Evening Standard. Retrieved 2010-06-29. 22. ^ "Do Nitrogen-Filled Tires Enhance Fuel-Efficiency?". Scientific American. September 30, 2008. Retrieved 2010-06-29. 23. ^ Tom and Ray Magliozzi (February 2005). "Dear Tom and Ray". CarTalk.com. Retrieved 2010-06-29. 24. ^ Petersen, Gene (October 4, 2007). "Tires - Nitrogen air loss study". Consumer Reports. Retrieved 2011-12-10. "Bottom line: Overall, consumers can use nitrogen and might enjoy the slight improvement in air retention provided, but it's not a substitute for regular inflation checks." 25. ^ "Understanding Retreading". International Tire & Rubber Association. Retrieved 201010-23.[dead link] 26. ^ "Retread Tires". U.S. Environmental Protection Agency. 2008-09-24. Retrieved 201010-23. 27. ^ Brodsky, Harvey. "Federal Government Endorses the Use of Retreaded Tires". Tire Retread Information Bureau. Retrieved 2010-10-23.[dead link] 28. ^ Yokohama 29. ^ SAE. "TKPH application". Retrieved October 7, 2007. 30. ^ Bridgestone. "How to use TKPH". Archived from the original on September 27, 2006. Retrieved October 7, 2007. 31. ^ Goodyear. "New temperature prediction model improves on current TKPH formula". Archived from the original on November 6, 2006. Retrieved October 7, 2007. 32. ^ Brown, Sheldon. "Sheldon Brown on tires". Retrieved 2008-07-01. 33. ^ Markus, Frank. "Racing Fast 'n' Cheap: Ice Racing". Motor Trend. Retrieved 2008-0930. 34. ^ My Kingdom for a Tire, Business Week, April 21, 2008, pp. 46–48 35. ^ My Kingdom for a Tire, Business Week, April 21, 2008, p. 48 36. ^ Federal Aviation Administration, Use of Nitrogen or Other Inert Gas for Tire Inflation in Lieu of Air 37. ^ Hogan, C. Michael (September 1973). "Analysis of highway noise". Journal of Water, Air, & Soil Pollution (Springer Verlag) 2 (3): 387–392. doi:10.1007/BF00159677. ISSN 0049-6979. 38. ^ Lecomte, C (2009). Validation of a Belt Model for Prediction of Hub Forces from a Rolling Tire. Tire Science & Technology 37.2. Retrieved 1 July 2009. 39. ^ ETRTO Standards Manual 2007. Bruxelles, Belgium: ETRTO. 2007. pp. I. 40. ^ "ABC News: Aged Tires Sold as 'New' by Big Retailers". Abcnews.go.com. Retrieved 2010-10-23. 41. ^ 05/09/2008 (2008-05-09). "Aged Tires: A Driving Hazard?". Abcnews.go.com. Retrieved 2010-10-23. 42. ^ Hossain, Mustaque; Nabors, Daniel (Jan–Feb 2005). Testing and evaluation of used automobile tires and recycled tire-derived materials for low-cost crash cushions. 36. Journal of Materials in Civil Engineering. Retrieved 2010-10-23. 43. ^ "Tire-Derived Fuel". U.S. Environmental Protection Agency. Retrieved 2011-12-29. 44. ^ Sullivan, Joseph P. (2006). "An Assessment of Environmental Toxicity and Potential Contamination from Artificial Turf using Shredded or Crumb Rubber" (PDF). Retrieved 2009-06-01.
45. ^ Chalker-Scott, Linda. "The Myth of Rubberized Landscapes" (PDF). Retrieved 200906-01.
External links
Look up inner tube in Wiktionary, the free dictionary. Look up tire or tyre in Wiktionary, the free dictionary. Wikimedia Commons has media related to: Tires
National Highway Traffic Safety Adm "Tire Safety" Brochure U.S. Government tire rating and maintenance site. [show]
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Tire manufacturing
From Wikipedia, the free encyclopedia Jump to: navigation, search This article is written like a personal reflection or essay rather than an encyclopedic description of the subject. Please help improve it by rewriting it in an encyclopedic style. (July 2012) This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (April 2009) Pneumatic tires are manufactured according to relatively standardized processes and machinery, in around 450 tire factories in the world. With over 1 billion tires manufactured worldwide annually, the tire industry is the major consumer of natural rubber. Tire factories start with bulk raw materials such as rubber, carbon black, and chemicals and produce numerous specialized components that are assembled and cured. This article describes the components assembled to make a tire, the various materials used, the manufacturing processes and machinery, and the overall business model.
The tire is an assembly of numerous components that are built up on a drum and then cured in a press under heat and pressure. Heat facilitates a polymerization reaction that crosslinks rubber monomers to create long elastic molecules. These polymers create the elastic quality that permits the tire to be compressed in the area where the tire contacts the road surface and spring back to its original shape under high-frequency cycles. Typical components used in tire assembly are listed below.
Contents
1 Inner liner 2 Body ply 3 Sidewall 4 Beads 5 Apex 6 Belt package 7 Tread 8 Cushion gum 9 Other components 10 Materials 11 Manufacturing process o 11.1 Compounding and mixing o 11.2 Component preparation o 11.3 Tire building o 11.4 Curing o 11.5 Final finish 12 Tire manufacturing companies 13 See also 14 References 15 External links
Inner liner
The inner liner is an extruded halobutyl rubber sheet compounded with additives that result in low air permeability. The inner liner assures that the tire will hold high-pressure air inside, without the air gradually diffusing through the rubber structure.[1]
Body ply
The body ply is a calendered sheet consisting of one layer of rubber, one layer of reinforcing fabric, and a second layer of rubber. The earliest textile used was cotton; later materials include rayon, nylon, polyester, and Kevlar. Passenger tires typically have one or two body plies. Body plies give the tire structure strength. Truck tires, off-road tires, and aircraft tires have progressively more plies. The fabric cords are highly flexible but relatively inelastic.
Sidewall
Sidewalls are non-reinforced extruded profiles with additives to give the sides of the tire good abrasion resistance and environmental resistance. Additives used in sidewall compounds include antioxidants and antiozonants. Sidewall extrusions are nonsymmetrical and provide a thick rubber area to enable molding of raised letters and sidewall ornamentation.
Beads
Beads are bands of high tensile-strength steel wire encased in a rubber compound. Bead wire is coated with special alloys of bronze or brass. Coatings protect the steel from corrosion. Copper in the alloy and sulfur in the rubber cross-link to produce copper sulfide, which improves bonding of the bead to the rubber. Beads are inflexible and inelastic, and provide the mechanical strength to fit the tire to the wheel. Bead rubber includes additives to maximize strength and toughness.
Apex
The apex is a triangular extruded profile that mates against the bead. The apex provides a cushion between the rigid bead and the flexible inner liner and body ply assembly. Alternatively called "filler" (as in the diagram above).
Belt package
Belts are calendered sheets consisting of a layer of rubber, a layer of closely spaced steel cords, and a second layer of rubber. The steel cords are oriented radially in radial tire construction, and at opposing angles in bias tire construction. Belts give the tire strength and dent resistance while allowing it to remain flexible. Passenger tires are usually made with two or three belts.
Tread
The tread is a thick extruded profile that surrounds the tire carcass. Tread compounds include additives to impart wear resistance and traction in addition to environmental resistance. Tread compound development is an exercise in compromise, as hard compounds have long wear characteristics but poor traction whereas soft compounds have good traction but poor wear characteristics.
Cushion gum
Many higher-performing tires include an extruded component between the belt package and the tread to isolate the tread from mechanical wear from the steel belts.
Other components
Tire construction methods vary somewhat in the number and type of components, as well as the compound formulations for each component, according to the tire use and price point. Tire makers continuously introduce new materials and construction methods in order to achieve higher performance at lower cost.
Materials
Natural rubber, or polyisoprene is the basic elastomer used in tire making Styrene-butadiene co-polymer (SBR) is a synthetic rubber which is often substituted in part for natural rubber based on the comparative raw materials cost Polybutadiene is used in combination with other rubbers because of its low heat-buildup properties Halobutyl rubber is used for the tubeless inner liner compounds, because of its low air permeability. The halogen atoms provide a bond with the carcass compounds which are mainly natural rubber. Bromobutyl is superior to chlorobutyl, but is more expensive
Carbon Black, forms a high percentage of the rubber compound. This gives reinforcement and abrasion resistance Silica, used together with carbon black in high performance tires, as a low heat build up reinforcement Sulphur crosslinks the rubber molecules in the vulcanization process Vulcanizing Accelerators are complex organic compounds that speed up the vulcanization Activators assist the vulcanization. The main one is zinc oxide Antioxidants and antiozonants prevent sidewall cracking due to the action of sunlight and ozone Textile fabric reinforces the carcass of the tire
Manufacturing process
Tire plants are traditionally divided into five departments that perform special operations. These usually act as independent factories within a factory. Large tire makers may set up independent factories on a single site, or cluster the factories locally across a region.
Compounding and mixing
SB R rubber compound to with chemicals formulations 1. 2. 3. 4. 5. 6. SB Rubber 100 k.g. carbon 220 50 k.g. zinc oxide 2.5 k.g. static acid 1.5 k.g. accelerator 1.2 k.g. Oil 3.5 k.g.
Compounding is the operation of bringing together all the ingredients required to mix a batch of rubber compound. Each component has a different mix of ingredients according to the properties required for that component. Mixing is the process of applying mechanical work to the ingredients in order to blend them into a homogeneous substance. Internal mixers are often equipped with two counter-rotating rotors in a large housing that shear the rubber charge along with the additives. The mixing is done in three or four stages to incorporate the ingredients in the desired order. The shearing action generates considerable heat, so both rotors and housing are water-cooled to maintain a temperature low enough to assure that vulcanization does not begin. After mixing, the rubber charge is dropped into a chute and fed by an extruding screw into a roller die. Alternatively, the batch can be dropped onto an open rubber mill batchoff system. A mill consists of twin counter-rotating rolls, one serrated, that provide additional mechanical working to the rubber and produce a thick rubber sheet. The sheet is pulled off the rollers in the form of a strip. The strip is cooled, dusted with talc, and laid down into a pallet bin.
The ideal compound at this point would have a highly uniform material dispersion; however in practice there is considerable non-uniformity to the dispersion. This is due to several causes, including hot and cold spots in the mixer housing and rotors, excessive rotor clearance, rotor wear, and poorly circulating flow paths. As a result, there can be a little more carbon black here, and a little less there, along with a few clumps of carbon black elsewhere, that are not well mixed with the rubber or the additives. Mixers are often controlled according to the power integration method, where the current flow to the mixer motor is measured, and the mixing terminated upon reaching a specified total amount of mix energy imparted to the batch.
Component preparation
Components fall into three classes based on manufacturing process: calendering, extrusion, and bead building. The extruder machine consists of a screw and barrel, screw drive, heaters, and a die. The extruder applies two conditions to the compound: heat and pressure. The extruder screw also provides for additional mixing of the compound through the shearing action of the screw. The compound is pushed through a die, after which the extruded profile is vulcanized in a continuous oven, cooled to terminate the vulcanization process, and either rolled up on a spool or cut to length. Tire treads are often extruded with four components in a quadraplex extruder, one with four screws processing four different compounds, usually a base compound, core compound, tread compound, and wing compound. Extrusion is also used for sidewall profiles and inner liners. The calender is a set of multiple large-diameter rolls that squeeze rubber compound into a thin sheet, usually of the order of 2 metres wide. Fabric calenders produce an upper and lower rubber sheet with a layer of fabric in between. Steel calenders do so with steel cords. Calenders are used to produce body plies and belts. A creel room is a facility that houses hundreds of fabric or wire spools that are fed into the calender. Calenders utilize downstream equipment for shearing and splicing calendered components.
Tire building
Tire building is the process of assembling all the components onto a tire building drum. Tirebuilding machines (TBM) can be manually operated or fully automatic. Typical TBM operations include the first-stage operation, where inner liner, body plies, and sidewalls are wrapped around the drum, the beads are placed, and the assembly turned up over the bead. In the second stage operation the belt package and tread are applied and the green tire is inflated and shaped. All components require splicing. Inner liner and body plies are spliced with a square-ended overlap. Tread and sidewall are joined with a skived splice, where the joining ends are bevel-cut. Belts are spliced end to end with no overlap. Splices that are too heavy or non-symmetrical will generate defects in force variation, balance, or bulge parameters. Splices that are too light or
open can lead to visual defects and in some cases tire failure. The final product of the TBM process is called a green tire, where green refers to the uncured state. Pirelli Tire developed a special process called MIRS that uses robots to position and rotate the building drums under stations that apply the various components, usually via extrusion and strip winding methods. This permits the equipment to build different tire sizes in consecutive operations without the need to change tooling or setups. This process is well suited to small volume production with frequent size changes. The largest tire makers have internally developed automated tire-assembly machines in an effort to create competitive advantages in tire construction precision, high production yield, and reduced labor. Nevertheless there is a large base of machine builders who produce tire-building machines.
Curing
Curing is the process of applying pressure to the green tire in a mold in order to give it its final shape, and applying heat energy to stimulate the chemical reaction between the rubber and other materials. In this process the green tire is automatically transferred onto the lower mold bead seat, a rubber bladder is inserted into the green tire, and the mold closes while the bladder inflates. As the mold closes and is locked the bladder pressure increases so as to make the green tire flow into the mold, taking on the tread pattern and sidewall lettering engraved into the mold. The bladder is filled with a recirculating heat transfer medium, such as steam, hot water, or inert gas. Temperatures are in the area of 350 degrees Fahrenheit with pressures around 350 PSI. Passenger tires cure in approximately 15 minutes. At the end of cure the pressure is bled down, the mold opened, and the tire stripped out of the mold. The tire may be placed on a PCI, or postcure inflator, that will hold the tire fully inflated while it cools. There are two generic curing press types, mechanical and hydraulic. Mechanical presses hold the mold closed via toggle linkages, while hydraulic presses use hydraulic oil as the prime mover for machine motion, and lock the mold with a breech-lock mechanism. Hydraulic presses have emerged as the most costeffective because the press structure does not have to withstand the mold-opening pressure and can therefore be relatively lightweight. There are two generic mold types, two-piece molds and segmental molds. Large off-road tires are often cured in ovens with cure times approaching 24 hours.
Final finish
After the tire has been cured, there are several additional operations. Tire uniformity measurement is a test where the tire is automatically mounted on wheel halves, inflated, run against a simulated road surface, and measured for force variation. Tire balance measurement is a test where the tire is automatically placed on wheel halves, rotated at a high speed and measured for imbalance. Large commercial truck/bus tires, as well as some passenger and light truck tires, are inspected by X-ray machines that can penetrate the rubber to analyze the steel cord structure.
In the final step, tires are inspected by human eyes for numerous visual defects such as incomplete mold fill, exposed cords, blisters, blemishes, and others.
Tire manufacturing companies
For a list of tire companies, List of tire companies.
See also
Retread
References
1. ^ http://www.goodyeartires.com/about/diversity/how_built.html
External links
The Tire Society
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From Wikipedia, the free encyclopedia Jump to: navigation, search This article is about tires used on road vehicles. For railroad tires, see railway tires. For other uses, see Tire (disambiguation).
Stacked and standing car tires A tire (in American English and Canadian English) or tyre (in some Commonwealth Nations such as UK, Australia and New Zealand) is a ring-shaped covering that fits around a wheel rim to protect it and enable better vehicle performance by providing a flexible cushion that absorbs shock while keeping the wheel in close contact with the ground. The word itself may be derived from the word "tie," which refers to the outer steel ring part of a wooden cart wheel that ties the wood segments together (see Etymology below). The fundamental materials of modern tires are synthetic rubber, natural rubber, fabric and wire, along with other compound chemicals. They consist of a tread and a body. The tread provides traction while the body ensures support. Before rubber was invented, the first versions of tires were simply bands of metal that fitted around wooden wheels to prevent wear and tear. Today, the vast majority of tires are pneumatic inflatable structures, comprising a doughnut-shaped body of cords and wires encased in rubber and generally filled with compressed air to form an inflatable cushion. Pneumatic tires are used on many types of vehicles, such as cars, bicycles, motorcycles, trucks, earthmovers, and aircraft.
Contents
1 Etymology and spelling 2 History 3 Manufacturing 4 Components 5 Associated components 6 Construction types
7 Specifications 8 Performance characteristics 9 Markings 10 Vehicle applications 11 Sound and vibration characteristics 12 Regulatory bodies 13 Safety 14 Asymmetric tire 15 See also 16 References 17 External links
Etymology and spelling
The Oxford English Dictionary suggests that the word derives from "attire",[1] while other sources suggest a connection with the verb "to tie".[2] From the 15th to the 17th centuries the spellings tire and tyre were used without distinction;[1] but by 1700 tyre had become obsolete and tire remained as the settled spelling.[1] In the UK, the spelling tyre was revived in the 19th century for pneumatic tires, though many continued to use tire for the iron variety. The Times newspaper in Britain was still using tire as late as 1905.[3] The 1911 edition of the Encyclopædia Britannica states that "[t]he spelling 'tyre' is not now accepted by the best English authorities, and is unrecognized in the US",[2] while Fowler's Modern English Usage of 1926 says that "there is nothing to be said for 'tyre', which is etymologically wrong, as well as needlessly divergent from our own [sc. British] older & the present American usage".[1] However, over the course of the 20th century tyre became established as the standard British spelling.
History
The earliest tires were bands of iron (later steel), placed on wooden wheels, used on carts and wagons. The tire would be heated in a forge fire, placed over the wheel and quenched, causing the metal to contract and fit tightly on the wheel. A skilled worker, known as a wheelwright, carried out this work. The outer ring served to "tie" the wheel segments together for use, providing also a wear-resistant surface to the perimeter of the wheel. The word "tire" thus emerged as a variant spelling to refer to the metal bands used to tie wheels. The first practical pneumatic tire was made by John Boyd Dunlop while working as a veterinarian in May Street, Belfast, Ireland in 1887 for his son's bicycle, in an effort to prevent the headaches his son had while riding on rough roads (Dunlop's patent was later declared invalid because of prior art by fellow Scot Robert William Thomson). Dunlop is credited with "realizing rubber could withstand the wear and tear of being a tire while retaining its resilience".[4] The development of this technology hinges on myriad engineering advances. In terms of materials, the vulcanization of natural rubber is credited to Charles Goodyear and Robert William Thomson. Synthetic rubbers were invented in the laboratories of Bayer in the
1920's.[5] Today, over 1 billion tires are produced annually in over 400 tire factories, see List of Tire Companies.
Manufacturing
Main article: Tire manufacturing Pneumatic tires are manufactured in around 450 tire factories in the world. Over 1 billion tires are manufactured annually, making the tire industry the major consumer of natural rubber. In 2015 1.72 billion tires are expected to be sold globally.[6] Tire production start with bulk raw materials such as rubber, carbon black, and chemicals and produce numerous specialized components that are assembled and cured. Many kinds of rubber are used, the most common being styrene-butadiene copolymer. This article describes the components assembled to make a tire, the various materials used, the manufacturing processes and machinery, and the overall business model.
Styrene-butadiene copolymer is the most popular material used in the production of rubber tires.[5] In 2004, $80 billion of tires were sold worldwide,[7] in 2010 it was $140 billion.[8] The top five tire manufacturing companies by revenue are Bridgestone, Michelin, Goodyear, Continental, and Pirelli.[9]
Components
A tire carcass is composed of several parts.
Tread
Main article: Tread
2 bicycle tires with different tread patterns The tread is the part of the tire that comes in contact with the road surface. The portion that is in contact with the road at a given instant in time is the contact patch. The tread is a thick rubber, or rubber/composite compound formulated to provide an appropriate level of traction that does not wear away too quickly. The tread pattern is characterized by the geometrical shape of the grooves, lugs, voids and sipes. Grooves run circumferentially around the tire, and are needed to channel away water. Lugs are that portion of the tread design that contacts the road surface. Voids are spaces between lugs that allow the lugs to flex and evacuate water. Tread patterns feature non-symmetrical (or non-uniform) lug sizes circumferentially to minimize noise levels at discrete frequencies. Sipes are valleys cut across the tire, usually perpendicular to the grooves, which allow the water from the grooves to escape to the sides in an effort to prevent hydroplaning. Treads are often designed to meet specific product marketing positions. High performance tires have small void ratios to provide more rubber in contact with the road for higher traction, but may be compounded with softer rubber that provides better traction, but wears quickly. Mud and snow (M&S) tires are designed with higher void ratios to channel away rain and mud, while providing better gripping performance. Specialized tires will always work better than general/all purpose/all weather tires when being used in the conditions the specialized tires are designed for. Tread lug Tread lugs provide the contact surface necessary to provide traction. As the tread lug enters the road contact area, or footprint, it is compressed. As it rotates through the footprint it is deformed circumferentially. As it exits the footprint, it recovers to its original shape. During the deformation and recovery cycle the tire exerts variable forces into the vehicle.[citation needed] These forces are described as Force Variation.[citation needed] Tread void Tread voids provide space for the lug to flex and deform as it enters and exits the footprint. Voids also provide channels for rainwater, mud, and snow to be channeled away from the footprint. The void ratio is the void area of the tire divided by the entire tread area. Low void areas have high contact area and therefore higher traction on clean, dry pavement. Rain groove The rain groove is a design element of the tread pattern specifically arranged to channel water away from the footprint. Rain grooves are circumferential in most truck tires. Many high performance passenger tires feature rain grooves that are angled from the center toward the sides of the tire.[citation needed] Some tire manufacturers claim that their tread pattern is designed to actively pump water out from under the tire by the action of the tread flexing.[citation needed] This results in a smoother ride in different types of weather.[citation needed]
Sipe Tread lugs often feature small narrow voids, or sipes, that improve the flexibility of the lug to deform as it traverses the footprint area. This reduces shear stress in the lug and reduces heat build up. Testing of identical siped and unsiped tires showed measurable improvements in snow traction and ice braking performance, however diminishing and extending braking distances on wet and dry pavement by a few feet on siped tires. Off-road tire enthusiasts have been siping tires for years for greater traction, as many manufacturers now offer already siped off-road-tires. Wear bar Wear bars (or wear indicators) are raised features located at the bottom of the tread grooves that indicate the tire has reached its wear limit. When the tread lugs are worn to the point that the wear bars connect across the lugs, the tires are fully worn and should be taken out of service. Most wear bars indicate a remaining tread depth of 1.6 millimetres (0.063 in) and are deemed "worn out" at that point.[10]
Bead
The bead is that part of the tire that contacts the rim on the wheel. The bead is typically reinforced with steel wire and compounded of high strength, low flexibility rubber. The bead seats tightly against the two rims on the wheel to ensure that a tubeless tire holds air without leakage. The bead fit is tight to ensure the tire does not shift circumferentially as the wheel rotates. The width of the rim in relationship to the tire is a factor in the handling characteristics of an automobile, because the rim supports the tire's profile.
Sidewall
Uneven sidewall wear, down to fabric plies, due to significant under-inflation The sidewall is that part of the tire that bridges between the tread and bead. The sidewall is largely rubber but reinforced with fabric or steel cords that provide for strength and flexibility. The sidewall transmits the torque applied by the drive axle to the tread to create traction. The sidewall, in conjunction with the air inflation, also supports the load of the vehicle. Sidewalls are molded with manufacturer-specific detail, government mandated warning labels, and other consumer information, and sometimes decorative ornamentation, like whitewalls.
Shoulder
The shoulder is that part of the tire at the edge of the tread as it makes transition to the sidewall.
Ply
Plies are layers of relatively inextensible cords embedded in the rubber[11] to hold its shape by preventing the rubber from stretching in response to the internal pressure. The orientations of the plies plays a large role in the performance of the tire and is one of the main ways that tires are categorized.
Associated components
Several additional components may be required in addition to just the tire to form a functional wheel.
Wheel
Main article: Wheel Tires are mounted onto wheels that have most often have integral rims on their outer edges to hold the tire. Automotive wheels are typically made from pressed and welded steel, or a composite of lightweight metal alloys, such as aluminum or magnesium. These alloy wheels may be either cast or forged. The mounted tire and wheel assembly is then bolted to the vehicle's hub. A decorative hubcap and trim ring may be placed over the wheel.
Rim
Main article: Rim (wheel) The beads of the tire are held on the rim, or the "outer edge" of a wheel.[12] These outer edges are shaped to obtain a proper shape on each side, having a radially cylindrical inclined inner wall on which the tire can be mounted. The wheel's rim must be of the proper design and type to hold the bead of the appropriately sized tire.[13] Tires are mounted on the wheel by forcing its beads into the channel formed by the wheel's inner and outer rims.[14]
Inner tube
Most bicycle tires, many motorcycle tires, and many tires for large vehicles such as buses, heavy trucks, and tractors are designed for use with inner tubes. Inner tubes are torus-shaped balloons made from an impermeable material, such as soft, elastic synthetic rubber, to prevent air leakage. The inner tubes are inserted into the tire and inflated to retain air pressure. Large inner tubes, which are large inflatable toruses, can be re-used for other purposes, such as swimming and rafting (see swim ring), tubing (recreation), sledding, and skitching. Purpose-built
inflatable toruses are also manufactured for these uses, offering choice of colors, fabric covering, handles, decks, and other accessories, and eliminating the protruding valve stem.
Schrader valve stem with its cap removed
Valve stem
Main article: Valve stem The valve stem is a tube made of metal or rubber, through which the tire is inflated, with a check valve, typically a Schrader valve on automobiles and most bicycle tires, or a Presta valve on high-performance bicycles. Valve stems usually protrude through the wheel for easy access. They mount directly to the rim, in the case of tubeless tires, or are an integral part of the inner tube. The rubber in valve stems eventually degrades, and, in the case of tubeless tires, replacement of the valve stem at regular intervals or with tire replacement reduces the chance of failure.
Construction types
A cross-section of a tire showing ply orientations
Bias
Bias tire (or cross ply) construction utilizes body ply cords that extend diagonally from bead to bead, usually at angles in the range of 30 to 40 degrees, with successive plies laid at opposing angles forming a crisscross pattern to which the tread is applied. The design allows the entire tire
body to flex easily, providing the main advantage of this construction, a smooth ride on rough surfaces. This cushioning characteristic also causes the major disadvantages of a bias tire: increased rolling resistance and less control and traction at higher speeds.
Belted bias
A belted bias tire starts with two or more bias-plies to which stabilizer belts are bonded directly beneath the tread. This construction provides smoother ride that is similar to the bias tire, while lessening rolling resistance because the belts increase tread stiffness. The plies and belts are at different angles, which improves performance compared to non-belted bias tires. The belts may be cord or steel.
Radial
Main article: Radial tire Radial tire construction utilizes body ply cords extending from the beads and across the tread so that the cords are laid at approximately right angles to the centerline of the tread, and parallel to each other, as well as stabilizer belts directly beneath the tread. The belts may be cord or steel. The advantages of this construction include longer tread life, better steering control, and lower rolling resistance. Disadvantages of the radial tire include a harder ride at low speeds on rough roads and in the context of off-roading, decreased "self-cleaning" ability and lower grip ability at low speeds.[15]
Solid
Many tires used in industrial and commercial applications are non-pneumatic, and are manufactured from solid rubber and plastic compounds via molding operations. Solid tires include those used for lawn mowers, skateboards, golf carts, scooters, and many types of light industrial vehicles, carts, and trailers. One of the most common applications for solid tires is for material handling equipment (forklifts). Such tires are installed by means of a hydraulic tire press.
Semi-pneumatic
Semi-pneumatic tires have a hollow center, but they are not pressurized. They are light-weight, low-cost, puncture proof, and provide cushioning.[16] These tires often come as a complete assembly with the wheel and even integral ball bearings. They are used on lawn mowers, wheelchairs, and wheelbarrows. They can also be rugged, typically used in industrial applications,[17] and are designed to not pull off their rim under use. Tires that are hollow but are not pressurized have also been designed for automotive use, such as the Tweel (a portmanteau of tire and wheel), which is an experimental tire design being developed at Michelin. The outer casing is rubber as in ordinary radial tires, but the interior has special compressible polyurethane springs to contribute to a comfortable ride. Besides the impossibility of going flat, the tires are intended to combine the comfort offered by higher-
profile tires (with tall sidewalls) with the resistance to cornering forces offered by low profile tires. They have not yet been delivered for broad market use.
Specifications
Tire pressure monitoring system
Main article: Tire pressure monitoring system Tire pressure monitoring systems (TPMS) are electronic systems that monitor the tire pressures on individual wheels on a vehicle, and alert the driver when the pressure goes below a warning limit. There are several types of designs to monitor tire pressure. Some actually measure the air pressure, and some make indirect measurements, such as gauging when the relative size of the tire changes due to lower air pressure.
Inflation pressure
Tires are specified by the vehicle manufacturer with a recommended inflation pressure, which permits safe operation within the specified load rating and vehicle loading. Most tires are stamped with a maximum pressure rating. For passenger vehicles and light trucks, the tires should be inflated to what the vehicle manufacturer recommends, which is usually located on a decal just inside the driver's door or in the vehicle owners handbook. Tires should not generally be inflated to the pressure on the sidewall; this is the maximum pressure, rather than the recommended pressure.[18] High performance and dynamic drivers often increase the tire pressure to near the maximum pressure as printed on the sidewall. This is done to sacrifice comfort for performance and safety. It is definitely very dangerous to allow tire pressure to drop below the recommended placard vehicle pressure, although this is commonly done temporarily when driving on sand to reduce chance of bogging. The reason for this is that it increases the amount of tire wall movement as a result of cornering forces. Should a low pressure tire be forced to perform an evasive maneuver, the tire wall will be more pliable than had it been of a higher pressure, and thus it will "roll" under the wheel. This increases the entire roll movement of the car, and diminishes tire contact area on the negative side of the vector. Thus only half the tire is in contact with the road, and the tire may deform to such an extent that the side wall on the positive vector side becomes in contact with the road. The probability of failing in the emergency maneuver is thus increased. Further, with low tire pressure—due to the side wall being more pliable—the tire will absorb more of the irregular forces from normal driving, and with this constant bending of the side wall as it absorbs the contours of the road, it heats up the tire wall to possibly dangerous temperatures, as well as degrades the steel wire reinforcement; this often leads to side wall blow-outs. In an extreme case of this phenomenon, the vehicle may drive into a pot-hole, or a hard elevation in the road. Due to the low tire pressure, the side wall at the contact area will temporarily collapse, thereby wedging the tire between the wheel and road, resulting in a tire laceration and blow-out, as well as a damaged wheel. High tire pressures are more inclined to keep its shape during any encounter, and will thus transmit the forces of the road to the suspension, rather than being damaged itself. This allows for an increased reaction speed, and "feel" the driver perceives of the
road. Modern tire designs allow for minimal tire contact surface deformity during high pressures, and as a result the traditional wear on the center of the tire due to reasonably high pressures is only known to very old or poorly designed tires. Feathering occurs on the junction between the tire tread and side wall, as a result of too low tire pressures. This is as a result of the inability of the tire to perform appropriately during cornering forces, leading to aberrant and shearing forces on the feathering area. This is due to the tire moving sideways underneath the wheel as the tire pressures are insufficient to transmit the forces to the wheel and suspension. It may be, that very high tire pressures have only two downsides: The sacrifice in comfort; and the increased chance of obtaining a puncture when driving over sharp objects, such as on a newly scraped gravel road. Many individuals have maintained their tire pressures at the maximum side wall printed value (inflated when cold) for the entire lifetime of the tire, with perfect wear until the end. This may be of negative economic value to the rubber and tire companies, as high tire pressures decrease wear, and minimize side wall blow outs. Many pressure gauges available at fuel stations have been de-calibrated by manhandling and the effect of time, and it is for this reason that vehicle owners should keep a personal pressure gauge with them to validate the correct tire pressure. During the early stages of tire engineering, and with current basic tires, the tire contact patch is readily reduced by both over-and-under inflation. Over-inflation may increase the wear on the center contact patch, and under-inflation will cause a concave tread, resulting in less center contact. Most modern tires will wear evenly at very high tire pressures, but will degrade prematurely due to low (or even standard) pressures. An increased tire pressure has many benefits, including decreased rolling resistance. It has been found, that an increased tire pressure almost exclusively results in shorter stopping distances, except in some circumstances that may be attributed to the low sample size.[19] If tire pressure is too low, the tire contact patch is changed more than if it were over-inflated. This increases rolling resistance, tire flexing, and friction between the road and tire. Under-inflation can lead to tire overheating, premature tread wear, and tread separation in severe cases.[20] Tires are not completely impermeable to air, and so lose pressure over time naturally. Some drivers inflate tires with nitrogen, instead of simple air, which is already 78% nitrogen, in an attempt to keep the tires at the proper inflation pressure longer,[21] though the effectiveness of this is debatable.[22][23][24]
Load rating
Tires are specified by the manufacturer with a maximum load rating. Loads exceeding the rating can result in unsafe conditions that can lead to steering instability and even rupture. For a table of load ratings, see tire code.
Speed rating
The speed rating denotes the maximum speed at which a tire is designed to be operated. For passenger vehicles these ratings range from 99 to 186 miles per hour (159 to 299 km/h). For a table of speed ratings, see tire code.
Service rating
Tires (especially in the U.S.) are often given service ratings, mainly used on bus and truck tires. Some ratings are for long haul, and some for stop-start multi-drop type work. Tires designed to run 500 miles (800 km) or more per day carrying heavy loads require special specifications.
Treadwear rating
Main article: Treadwear rating The treadwear rating or treadwear grade describes how long the tire manufacturers expect the tire to last. A Course Monitoring Tire (the standard tire that a test tire will be compared to) has a rating of "100". If a manufacturer assigns a treadwear rating of 200 to a new tire, they are indicating that they expect the new tire to have a useful lifespan that is 200% of the life of a Course Monitoring Tire. The "test tires" are all manufacturer-dependent. Brand A's rating of 500 is not necessarily going to give you the same mileage rating as Brand B's tire of the same rating. The testing is non-regulated and can vary greatly. Treadwear ratings are only useful for comparing Brand A's entire lineup against itself. Tread wear, also known as tire wear, is caused by friction between the tire and the road surface. Government legal standards prescribe the minimum allowable tread depth for safe operation.
Rotation
Tires may exhibit irregular wear patterns once installed on a vehicle and partially worn. Furthermore, front-wheel drive vehicles tend to wear the front tires at a greater rate compared to the rears. Tire rotation is the procedure of moving tires to different car positions, such as frontto-rear, in order to even out the wear, thereby extending the life of the tire. However care must be taken with unidirectional tires (tires that are designed to rotate in one direction only, for a vehicle that is going forward) so that the correct rotational direction - indicated on the side wall with an arrow-like symbol - is maintained after the swap.
Wheel alignment
Main article: Wheel alignment When mounted on the vehicle, the wheel and tire may not be perfectly aligned to the direction of travel, and therefore may exhibit irregular wear. If the discrepancy in alignment is large, then the irregular wear will become substantial if left uncorrected. Wheel alignment is the procedure for checking and correcting this condition through adjustment of camber, caster and toe angles. These settings also affect the handling characteristics of the vehicle.
Retread
Main article: Retread Tires that are fully worn can be re-manufactured to replace the worn tread. This is known as retreading or recapping, a process of buffing away the worn tread and applying a new tread.[25] Retreading is economical for truck tires because the cost of replacing the tread is less than the price of a new tire. Retreading passenger tires is less economical because the cost of retreading is high compared to the price of new cheap tires, but favorable compared to high-end brands. Worn tires can be retreaded by two methods, the mold or hot cure method and the pre-cure or cold one. The mold cure method involves the application of raw rubber on the previously buffed and prepared casing, which is later cured in matrices. During the curing period, vulcanization takes place and the raw rubber bonds to the casing, taking the tread shape of the matrix. On the other hand, the pre-cure method involves the application of a ready-made tread band on the buffed and prepared casing, which later is cured in an autoclave so that vulcanization can occur. During the retreading process, retread technicians must ensure the casing is in the best condition possible to minimize the possibility of a casing failure. Casings with problems such as capped tread, tread separation, unrepairable cuts, corroded belts or sidewall damage, or any run-flat or skidded tires, will be rejected. In most situations, retread tires can be driven under the same conditions and at the same speeds as new tires with no loss in safety or comfort.[26] The percentage of retread failures should be about the same as for new tire failures, but many drivers, including truckers, are guilty of not maintaining proper air pressure on a regular basis, and, if a tire is abused (overloaded, underinflated, or mismatched to the other tire on a set of duals), then that tire (new or recapped) will fail.[27] Many commercial trucking companies put retreads only on trailers, using only new tires on their steering and drive wheels. This procedure increases the driver's chance of maintaining control in case of problems with a retreaded tire.
Performance characteristics
The interaction of a tire with the pavement is a very complex phenomenon. Many of the details are modeled in Pacejka's Magic Formula. Some are explained below.
Balance
Main article: Tire balance When a wheel and tire rotate, they exert a centrifugal force on the axle that depends on the location of their center of mass and the orientation of their moment of inertia. This is referred to as balance, imbalance, or unbalance. Tires are checked at the point of manufacture for excessive static imbalance and dynamic imbalance using automatic tire balance machines. Tires are
checked again in the auto assembly plant or tire retail shop after mounting the tire to the wheel. Assemblies that exhibit excessive imbalance are corrected by applying balance weights to the wheels to counteract the tire/wheel imbalance. To facilitate proper balancing, most high performance tire manufacturers place red and yellow marks on the sidewalls to enable the best possible match-mounting of the tire/wheel assembly. There are two methods of match-mounting high performance tire to wheel assemblies using these red (uniformity) or yellow (weight) marks.[28]
Camber thrust
Main article: Camber thrust Camber thrust and camber force are terms used to describe the force generated perpendicular to the direction of travel of a rolling tire due to its Camber angle and finite contact patch.
Centrifugal growth
A tire rotating at higher speeds tends to develop a larger diameter, due to centrifugal forces that force the tread rubber away from the axis of rotation. This may cause speedometer error. As the tire diameter grows, the tire width decreases. This centrifugal growth can cause rubbing of the tire against the vehicle at high speeds. Motorcycle tires are often designed with reinforcements aimed at minimizing centrifugal growth.[citation needed]
Circle of forces
Main article: Circle of forces The circle of forces, traction circle, friction circle, or friction ellipse is a useful way to think about the dynamic interaction between a vehicle's tire and the road surface.
Contact patch
Main article: contact patch The contact patch, or footprint, of the tire, is the area of the tread that is in contact with the road surface. This area transmits forces between the tire and the road via friction. The length-to-width ratio of the contact patch affects steering and cornering behavior.
Cornering force
Main article: Cornering force Cornering force or side force is the lateral (i.e. parallel to the road surface) force produced by a vehicle tire during cornering.
Dry traction
Dry traction is measure of the tire's ability to deliver traction, or grip, under dry conditions. Dry traction is a function of the tackiness of the rubber compound.
Force variation
The tire tread and sidewall elements undergo deformation and recovery as they enter and exit the footprint. Since the rubber is elastomeric, it is deformed during this cycle. As the rubber deforms and recovers, it imparts cyclical forces into the vehicle. These variations are collectively referred to as tire uniformity. Tire uniformity is characterized by radial force variation (RFV), lateral force variation (LFV) and tangential force variation. Radial and lateral force variation is measured on a force variation machine at the end of the manufacturing process. Tires outside the specified limits for RFV and LFV are rejected. Geometric parameters, including radial runout, lateral runout, and sidewall bulge, are measured using a tire uniformity machine at the tire factory at the end of the manufacturing process as a quality check. In the late 1990s, Hunter Engineering introduced the GSP9700 Road Force balancer, which is equipped with a load roller similar to the force variation machine used at the factory to grade tire uniformity. This machine can find the best position for the tire on a given wheel so that the over-all assembly is as round as possible.
Load sensitivity
Main article: Tire load sensitivity Load sensitivity is the behaviour of tires under load. Conventional pneumatic tires do not behave as classical friction theory would suggest. Namely, the load sensitivity of most real tires in their typical operating range is such that the coefficient of friction decreases as the vertical load, Fz, increases.
Pneumatic trail
Main article: Pneumatic trail Pneumatic trail of a tire is the trail-like effect generated by compliant tires rolling on a hard surface and subject to side loads, as in a turn. More technically, it is the distance that the resultant force of side-slip occurs behind the geometric center of the contact patch.
Relaxation length
Main article: Relaxation length Relaxation length is the delay between when a slip angle is introduced and when the cornering force reaches its steady-state value.
Rolling resistance
Main article: Rolling resistance Rolling resistance is the resistance to rolling caused by deformation of the tire in contact with the road surface. As the tire rolls, tread enters the contact area and is deformed flat to conform to the roadway. The energy required to make the deformation depends on the inflation pressure, rotating speed, and numerous physical properties of the tire structure, such as spring force and stiffness. Tire makers seek lower rolling resistance tire constructions to improve fuel economy in cars and especially trucks, where rolling resistance accounts for a high proportion of fuel consumption. Pneumatic tires also have a much lower rolling resistance than solid tires. Because the internal air pressure acts in all directions, a pneumatic tire is able to "absorb" bumps in the road as it rolls over them without experiencing a reaction force opposite to the direction of travel, as is the case with a solid (or foam-filled) tire. The difference between the rolling resistance of a pneumatic and solid tire is easily felt when propelling wheelchairs or baby buggies fitted with either type so long as the terrain has a significant roughness in relation to the wheel diameter.[citation needed]
Self aligning torque
Main article: Self aligning torque Self aligning torque, also known as the aligning torque, SAT or Mz, is the torque that a tire creates as it rolls along that tends to steer it, i.e. rotate it around its vertical axis.
Slip angle
Main article: Slip angle Slip angle or sideslip angle is the angle between a rolling wheel's actual direction of travel and the direction towards which it is pointing (i.e., the angle of the vector sum of wheel translational velocity and sideslip velocity ).
Stopping distance
Performance-oriented tires have a tread pattern and rubber compounds designed to grip the road surface, and so usually have a slightly shorter stopping distance. However, specific braking tests are necessary for data beyond generalizations.
Work load
The work load of a tire is monitored so that it is not put under undue stress, which may lead to its premature failure.[29] Work load is measured in ton kilometre per hour (TKPH). The measurement's appellation and units are the same. The recent shortage and increasing cost of tires for heavy equipment has made TKPH an important parameter in tire selection and equipment maintenance for the mining industry. For this reason, manufacturers of tires for large earth-moving and mining vehicles assign TKPH ratings to their tires based on their size,
construction, tread type, and rubber compound.[30][31] The rating is based on the weight and speed that the tire can handle without overheating and causing it to deteriorate prematurely. The equivalent measure used in the United States is ton mile per hour (TMPH).
Tread wear
There are several types of abnormal tread wear. Poor wheel alignment can cause excessive wear of the innermost or outermost ribs. Gravel roads, rocky terrain, and other rough terrain causes accelerated wear. Over-inflation above the sidewall maximum can cause excessive wear to the center of the tread. Modern tires have steel belts built in to prevent this. Under-inflation causes excessive wear to the outer ribs. Often, the placard pressure is too low and most tires are underinflated as a result.[citation needed] Unbalanced wheels can cause uneven tire wear, as the rotation may not be perfectly circular. Tire manufacturers and car companies have mutually established standards for tread wear testing that include measurement parameters for tread loss profile, lug count, and heel-toe wear. See also Work load above.
Wet traction
Wet traction is the tire's traction, or grip, under wet conditions. Wet traction is improved by the tread design's ability to channel water out of the tire footprint and reduce hydroplaning. However, tires with a circular cross-section, such as those found on racing bicycles, when properly inflated have a sufficiently small footprint to not be susceptible to hydroplaning. For such tires, it is observed that fully slick tires will give superior traction on both wet and dry pavement.[32]
Markings
DOT code
In the United States, the DOT Code is an alphanumeric character sequence molded into the sidewall of the tire for purposes of tire identification. The DOT Code is mandated by the U.S. Department of Transportation. The DOT Code is useful in identifying tires in a product recall. The DOT Code begins with the letters "DOT" followed by a plant code (two numbers or letters) that identifies where it was manufactured. The last four numbers represent the week and year the tire was built. A three-digit code was used for tires manufactured before 2000. For example, 178 means it was manufactured in the 17th week of 8th year of the decade. In this case it means 1988. For tires manufactured in the 1990s, the same code holds true, but there is a little triangle (Δ) after the DOT code. Thus, a tire manufactured in the 17th week of 1998 would have the code 178Δ. In 2000, the code was switched to a 4-digit code. Same rules apply, so for example, 3003 means the tire was manufactured in the 30th week of 2003. Other numbers are marketing codes used at the manufacturer's discretion.
E-mark
All tires sold for road use in Europe after July 1997 must carry an E-mark. The mark itself is either an upper case "E" or lower case "e" – followed by a number in a circle or rectangle, followed by a further number. An (upper case) "E" indicates that the tire is certified to comply with the dimensional, performance and marking requirements of ECE regulation 30. A (lower case) "e" indicates that the tire is certified to comply with the dimensional, performance and marking requirements of Directive 92/23/EEC. The number in the circle or rectangle denotes the country code of the government that granted the type approval. The last number outside the circle or rectangle is the number of the type approval certificate issued for that particular tire size and type.
Mold serial number
Tire manufacturers usually embed a mold serial number into the sidewall area of the mold, so that the tire, once molded, can be traced back to the mold of original manufacturer.
Codes
Main article: Tire code
Vehicle applications
Tires are classified into several standard types, based on the type of vehicle they serve. Since the manufacturing process, raw materials, and equipment vary according to the tire type, it is common for tire factories to specialize in one or more tire types. In most markets, factories that manufacture passenger and light truck radial tires are separate and distinct from those that make aircraft or off-the-road (OTR) tires.[citation needed]
Passenger vehicles and light truck
High performance High performance tires are designed for use at higher speeds, and more often, a more "sporty" driving style. They feature a softer rubber compound for improved traction, especially on high speed cornering. The trade off of this softer rubber is shorter tread life. High performance street tires sometimes sacrifice wet weather handling by having shallower water channels to provide more actual rubber tread surface area for dry weather performance.[citation needed] The ability to provide a high level of performance on both wet and dry pavement varies widely among manufacturers, and even among tire models of the same manufacturer. This is an area of active research and development, as well as marketing. Mud and snow Main article: Snow tires
The examples and perspective in this section may not represent a worldwide view of the subject. Please improve this article and discuss the issue on the talk page. (July 2010) Mud and Snow, (or M+S, or M&S), is a designation applied rather arbitrarily by manufacturers for all-season and winter tires designed to provide improved performance under low temperature conditions, compared to summer tires. The tread compound is usually softer than that used in tires for summer conditions, thus providing better grip on ice and snow, but wears more quickly at higher temperatures. Tires may have well above average numbers of sipes in the tread pattern to grip the ice. There are no traction performance requirements which such a tire has to meet; M&S relates to the percentage of tread void area. Dedicated winter tires will bear the "Mountain/Snowflake Pictograph" if designated as a winter/snow tire by the American Society for Testing & Materials. Winter tires will typically also carry the designation MS, M&S, or the words MUD AND SNOW (but see All-season tires, below).
Studded, highly siped, winter tire Some winter tires may be designed to accept the installation of metal studs for additional traction on icy roads. The studs also roughen the ice, thus providing better friction between the ice and the soft rubber in winter tires. Use of studs is restricted in most countries with the notable exception of the Nordic countries where they are commonly used during the winter season outside metropolitan areas, and even prohibited in some locales due to the increased road wear caused by studs. Typically, studs are never used on heavier vehicles, except ice resurfacers. The upper tier classes of ice racing[33] and rallying mandates the vehicles be equipped with studded tires. Other winter tires rely on factors other than studding for traction on ice, e.g. highly porous or hydrophilic rubber that adheres to the wet film on the ice surface. Some jurisdictions may require snow tires or tire chains on vehicles driven in certain areas during extreme weather conditions.
Mud tires are speciality tires with large, chunky tread patterns designed to bite into muddy surfaces. The large, open design also allows mud to clear quickly from between the lugs. Mud terrain tires also tend to be wider than other tires, to spread the weight of the vehicle over a greater area to prevent the vehicle from sinking too deeply into the mud. However in reasonable amounts of mud and snow, tires should be thinner. Being thinner, the tire will have more pressure on the road surface, thus allowing the tires to penetrate the snow layer and grip harder snow or road surface beneath. This does not compensate when the snow is too deep for such penetration, where the vehicle will sink into the snow and plough the snow in front and eventually pack it beneath it until the wheels no longer have traction. In this case, wider tires are preferred, as they have a larger contact patch and are better able to 'float' on top of the mud or snow. All season The All Season tire classification is a compromise between one developed for use on dry and wet roads during summer and one developed for use under winter conditions. The type of rubber and the tread pattern best suited for use under summer conditions cannot, for technical reasons, give good performance on snow and ice. The all-season tire is a compromise, and is neither an excellent summer tire nor an excellent winter tire. They have, however, become ubiquitous as original and replacement equipment on automobiles marketed in the United States, due to their convenience and their adequate performance in most situations. Even so, in other parts of the world, like Germany, it is common to have a designated tire set for winter and summer. AllSeason tires are also marked for mud and snow the same as winter tires but rarely with a snowflake. Owing to the compromise with performance during summer, winter performance is usually poorer than a winter tire. All-terrain All-terrain tires are typically used on SUVs and light trucks. These tires often have stiffer sidewalls for greater resistance against puncture when traveling off-road, the tread pattern offers wider spacing than all-season tires to remove mud from the tread. Many tires in the all-terrain category are designed primarily for on-road use, particularly all-terrain tires that are originally sold with the vehicle. Spare Main article: spare tire Some vehicles carry a spare tire, already mounted on a wheel, to be used in the event of flat tire or blowout. Minispare, or "space-saver spare" tires are smaller than normal tires to save on trunk/boot space, gas mileage, weight, and cost. Minispares have a short life expectancy and a low speed rating, often below 60 miles per hour (97 km/h). Run-flat Main article: Run-flat tire
Several innovative designs have been introduced that permit tires to run safely with no air for a limited range at a limited speed. These tires typically feature strong, load-supporting sidewalls. An infamous example of an alternate run-flat technology has plastic load-bearing inserts attached to the rim instead of the reinforced sidewalls. A disadvantage is that run-flat tires cannot be repaired if a puncture occurs, this is due to manufacturer's informing the automotive industry that you cannot tell what kind of state the sidewall is in due to the compacted sidewall of rubber.
Heavy duty truck
Heavy load may require multiple tires Heavy duty tires are also referred to as Truck/Bus tires. These are the tire sizes used on vehicles such as commercial freight trucks, dump trucks, and passenger buses. Truck tires are subcategorized into specialties according to vehicle position such as steering, drive axle, and trailer. Each type is designed with the reinforcements, material compounds, and tread patterns that best optimize the tire performance. A relatively new concept is the use of "Super Singles" or Wide Singles. Generally in a dual configuration, there are 2 tires per position, each between 275 mm295 mm wide. The Super Single replaces these with a single tire, usually 455 mm wide. This allows for less tread to be contacting the ground and also eliminates 2 sidewalls per position. Along with the weight savings of about 91 kilograms (200 lb) per axle, this enables vehicles using these to improve fuel economy.
Off-the-road
Off-the-road (OTR) tires being transported Off-the-road (OTR) tires include tires for construction vehicles such as wheel loaders, backhoes, graders, trenchers, and the like; as well as large mining trucks. OTR tires can be of either bias or radial construction although the industry is trending toward increasing use of radial. Bias OTR tires are built with a large number of reinforcing plies to withstand severe service conditions and high loads. Dramatically increasing commodity prices has led to shortages of new tires. As a consequence, multi-million dollar trucks can be idled for lack of tires, costing mines millions of dollars in lost productivity. This has led to a stronger effort to recycle old OTR tires. As of 2008, a new OTR tire can cost up to $50,000; retread tires are sold at half the price of new tires, and last 80% as long.[34] Retreading an OTR tire is labor intensive. First, the retreading technician must place the old tire in a buffing machine to remove what remains of the old tread; "skiving" follows this, which is the removal, by hand, of material the buffing misses. Next, the technician must inspect the tire, repairing defects. Lastly, the technician fills holes in the tire with rubber, applies a cement gum adhesive, and places the tire on a machine that will apply a new tread.[35]
Agricultural
The agricultural tire classification includes tires used on farm vehicles, typically tractors and specialty vehicles like harvesters. Driven wheels have very deep, widely spaced lugs to allow the tire to grip soil easily. High flotation tires are used in swampy environments and where soil compaction is a concern, featuring large footprints at low inflation pressures.
Racing
NASCAR tires Racing tires are highly specialized according to vehicle and race track conditions. This classification includes tires for drag racing, Auto-x, drifting, Time Attack, Road Racing – as well as the large-market race tires for Formula One, IndyCar, NASCAR, rallying, MotoGP and the like. Tires are specially engineered for specific race tracks according to surface conditions, cornering loads, and track temperature. Racing tires often are engineered to minimum weight targets, so tires for a 500 miles (800 km) race may run only 100 miles (160 km) before a tire change. Some tire makers invest heavily in race tire development as part of the company's marketing strategy and a means of advertising to attract customers. Racing tires often are not legal for normal highway use.
Industrial
Airless tire The Industrial tire classification is a bit of a catch-all category and includes pneumatic and nonpneumatic tires for specialty industrial and construction equipment such as skid loaders and fork lift trucks.
Bicycle
Main article: Bicycle tire
A bicycle tire in the style of a cruiser This classification includes all forms of bicycle tires, including road racing tires, mountain bike tires, snow tires, and tubular tires, used also with other human-powered vehicles (see Category:Human-powered vehicles).
Aircraft
Changing a tire on a P-3C Orion aircraft Aircraft tires are designed to withstand extremely heavy loads for short durations. The number of tires required for aircraft increases with the weight of the plane (because the weight of the airplane has to be distributed better). Aircraft tire tread patterns are designed to facilitate stability in high crosswind conditions, to channel water away to prevent hydroplaning, and for braking effect. Aircraft tires are usually inflated with nitrogen or helium to minimize expansion and contraction from extreme changes in ambient temperature and pressure experienced during flight.[citation needed] Dry nitrogen expands at the same rate as other dry atmospheric gases, but common compressed air sources may contain moisture, which increases the expansion rate with temperature.[citation needed] Aircraft tires generally operate at high pressures, up to 200 pounds per square inch (14 bar; 1,400 kPa) for airliners, and even higher for business jets. Tests of airline aircraft tires have shown that they are able to sustain pressures of maximum 800 pounds per square inch (55 bar; 5,500 kPa) before bursting. During the test the tires have to be filled with water, instead of helium or nitrogen, which is the common content of aircraft tires, to prevent the test room being blown apart by the energy when the tire bursts.
Aircraft tires also include heat fuses, designed to melt at a certain temperature. Tires often overheat if maximum braking is applied during an aborted takeoff or an emergency landing. The fuses provide a safer failure mode that prevents tire explosions by deflating in a controlled manner, thus minimizing damage to aircraft and objects in the surrounding environment. The requirement that an inert gas, such as nitrogen, be used instead of air for inflation of tires on certain transport category airplanes was prompted by at least three cases in which the oxygen in air-filled tires combined with volatile gases given off by a severely overheated tire and exploded upon reaching autoignition temperature. The use of an inert gas for tire inflation will eliminate the possibility of a tire explosion.[36]
Motorcycle
Main article: Motorcycle tyre There are many different types of motorcycle tires: This section's factual accuracy is disputed. (April 2008) Sport Touring – these tires are generally not used for high cornering loads, but for long straights, good for riding across the country. Sport Street – these tires are for aggressive street riders that spend most of their time carving corners on public roadways. These tires do not have a long life, but in turn have better traction in high speed cornering. Street and sport street tires have good traction even when cold, but when warmed too much, can actually lose traction as their internal temperature increases. Track or Slick – these tires are for track days or races. They have more of a triangular form, which in turn gives a larger contact patch while leaned over. These tires are not recommended for the street by manufacturers, and are known to have a shorter life on the street. Due to the triangulation of the tire, there will be less contact patch in the center, causing the tire to develop a flat spot quicker when used to ride on straightaways for long periods of time and have no tread so they lose almost all grip in wet conditions. Racing slicks are also made of a harder rubber compound and do not provide as much traction as street tires until warmed to a higher internal temperature than street tires normally operate at. Most street riding will not put a sufficient amount of friction on the tire to maintain the optimal tire temperature, especially in colder climates and in spring and fall.
Sound and vibration characteristics
Main article: Roadway noise The design of treads and the interaction of specific tire types with the roadway surface type produces considerable effect upon sound levels or noise pollution emanating from moving vehicles. These sound intensities increase with higher vehicle speeds.[37] The acoustic intensity
produced varies considerably depending on the tire tread design and the road surface type. There is a study "under development" that aims predict the interior noise due to the vibrations of a rolling tire structurally transmitted to the hub of a vehicle".[38]
Regulatory bodies
DOT
The United States Department of Transportation (DOT) is the U.S. governmental body authorized by the U.S. Congress to establish and regulate transportation safety in the United States of America.
NHTSA
The National Highway and Traffic Safety Administration (NHTSA) is a U.S. government body within the Department of Transportation tasked with regulating automotive safety in the United States.
UTQG
The Uniform Tire Quality Grading System (UTQG), is a system for comparing the performance of tires, established by the United States National Highway Traffic Safety Administration according to the Code of Federal Regulations 49 CFR 575.104. The UTQG regulation requires labeling of tires for tread wear, traction, and temperature.
T&RA
The Tire and Rim Association (T&RA) is a voluntary U.S. standards organization to promote the interchangeability of tires and rim and allied parts. Of particular interest, they published key tire dimension standards, key rim contour dimension standards, key tire valve dimension standards, and load / inflation standards.
ETRTO
The European Tyre and Rim Technical Organization (ETRTO) is the European standards organization "to establish engineering dimensions, load/pressure characteristics and operating guidelines" .[39] for tires, rims and valves. It is analogous to T&RA.
JATMA
The Japanese Automobile Tire Manufacturers Association (JATMA) is the Japanese standards organization for tires, rims and valves. It is analogous to T&RA and ETRTO.
TREAD Act
The Transportation Recall Enhancement, Accountability and Documentation Act (TREAD Act) is a United States federal law that sets standards for testing and the reporting of information related to products involved with transportation such as cars and tires.
RFID tags
Radio Frequency IDentification tags (RFID) are passive transponders affixed to the inside of the tire for purposes of automatic identification.[citation needed] Tags are encoded with various types of manufacturing data, including the manufacturer's name, location of manufacture, tire type, manufacturing date, and in some cases test data. RFID transponders can remotely read this data automatically. RFID tags are used by auto assemblers to identify tires at the point of assembly to the vehicle.[citation needed] Fleet operators utilize RFID as part of tire maintenance operations. CCC (China Compulsory Certification) is a mandatory certification system concerning product safety in China that went into effect in August 2002. Before CCC, there were two certification systems in China: CCIB and CCEE. With China's entrance into the WTO, these two systems were unified into the CCC certification system. After the termination of a one-year grace period in August 2003, the system became compulsory.The CCC certification system is operated by the State General Administration for Quality Supervision and Inspection and Quarantine of the People's Republic of China (AQSIQ) and the Certification and Accreditation Administration of the People's Republic of China (CNCA).
Safety
Proper vehicle safety requires specific attention to inflation pressure, tread depth, and general condition of the tires. Over-inflated tires run the risk of explosive decompression (they may pop). On the other hand, under-inflated tires have a higher rolling resistance and suffer from overheating and rapid tread wear particularly on the edges of the tread. Excessive tire wear will reduce steering and braking response,[citation needed] and tires worn down past their safety margins and into the casing run the very real risk of rupturing. Also, certain combinations of cross ply and radial tires on different wheels of the same vehicle can lead to vehicle instability, and may also be illegal. Vehicle and tire manufacturers provide owners' manuals with instructions on how to check and maintain tires.
Flat
Main article: Flat tire
A flat tire A flat tire occurs when a tire deflates. This can occur as a result of normal wear-and-tear, a leak, or more serious damage. A tire that has lost sufficient pressure will impair the stability of the vehicle and may damage the tire further if it is driven in this condition. The tire should be changed and/or repaired before it becomes completely flat. Continuing to drive a vehicle with a flat tire will damage the tire beyond repair, possibly damage the rim and vehicle, and put the occupants and other vehicles in danger. A flat tire or low-pressure tire should be considered an emergency situation, requiring immediate attention. Some tires, known as "run-flat tires", have either extremely stiff sidewalls or a resilient filler to allow driving a limited distance while flat, usually at reduced speed, without permanent damage or hazard. A modern radial tire may not be visibly distorted even with dangerously low inflation pressure. (This is especially true of tires with a low aspect ratio, sometimes known as "low profile" tires.) Thus maintenance of adequate tire pressure can have important safety implications despite the fact that most car owners neglect it. Tire designers have tried to make new tires fail-safe so that the failure of the operator to maintain the tire pressure won't cause a major safety concern, but there are limitations on this.
Hydroplaning (or aquaplaning)
Main article: Hydroplaning (road vehicle) Hydroplaning, also known as aquaplaning, is the condition where a layer of water builds up between the tire and road surface. Hydroplaning occurs when the tread pattern cannot channel away enough water at an adequate rate to ensure a semi-dry footprint area. When hydroplaning occurs, the tire effectively "floats" above the road surface on a cushion of water – and loses traction, braking and steering, creating a very unsafe driving condition. When hydroplaning occurs, there is considerably less responsiveness of the steering wheel. The correction of this unsafe condition is to gradually reduce speed, by merely lifting off the accelerator/gas pedal. Hydroplaning becomes more prevalent with wider tires (because of the lower weight per contact area) and especially at higher speeds; it is of virtually no concern to bicycle tires under normal riding conditions largely because of the lower speeds. The chance of car hydroplaning is also minimal at bicycle speeds as the weight per contact area of car tires is not much lower if any than bicycle tires.
Dangers of aged tires
Research and tests show that as tires age, they begin to dry out and become potentially dangerous, even if unused. Aged tires may appear to have similar properties to newly manufactured tires, but rubber degrades over time, and once the vehicle is traveling at high speeds (i.e. on a freeway) the tread could peel off, leading to severe loss of control. In tropical climates, such as Singapore, tires degrade sooner than in temperate climates, and more care should be taken in these climates to ensure that tires do not fail.[citation needed] Also, tires on
seldom-used trailers are at the greatest risk of age-failure, but some tires are built to withstand idleness, usually with nylon reinforcement. Many automakers recommend replacing tires after six years, and several tire manufacturers (Bridgestone, Michelin) have called for tires to be removed from service 10 years after the date of manufacture. However, an investigative report by Brian Ross on ABC's 20/20 news magazine found that many major retailers such as Goodyear, Wal-Mart, and Sears were selling tires that had been produced six or more years ago. Currently, no law for aged tires exists in the United States.[40][41]
Scrap tires and environmental issues
A child plays in a playground made from recycled tires. Guelph, Canada Once tires are discarded, they are considered scrap tires. Scrap tires are often re-used for things from bumper car barriers to weights to hold down tarps. Some facilities are permitted to recycle scrap tires through chipping, and processing into new products, or selling the material to licensed power plants for fuel. Some tires may also be retreaded for re-use. One group did "a study to evaluate the possibility of using scrap tires as a crash cushion system. The objective of this study was to evaluate the material properties of used tires and recycled tire-derived materials for use in low-cost, reusable crash cushions".[42] An interesting use, developed over 30 years back but not yet universally used, is to process scrap tires as raw material for roads. The process is removing the metal, granulating the rubber and then a chemical process where it is mixed with other usual materials for macadamised roads. The resulting roads have proved to have better waterproofing, more resilent resulting in a smoother ride and also longer tire life. Several countries (for example, South Korea) have regulations requiring its use, but most do not. Americans generate about 285 million scrap tires per year.[43] Many states have regulations as to the number of scrap tires that you may have on site, due to concerns with dumping, fire hazards, and mosquitoes. In the past, millions of tires have been discarded into open fields. This creates a breeding ground for mosquitoes, since the tires often hold water inside and remain warm enough for mosquito breeding. Mosquitoes create a nuisance and may increase the likelihood of spreading disease. It also creates a fire danger, since such a large tire pile is a lot of fuel. Some tire fires have burned for months, since water does not adequately penetrate or cool the burning tires. Tires have been known to liquefy, releasing hydrocarbons and other contaminants to the
ground and even ground water, under extreme heat and temperatures from a fire. The black smoke from a tire fire causes air pollution and is a hazard to down wind properties. The use of scrap tire chips for landscaping has become controversial, due to the leaching of metals and other contaminants from the tire pieces. Zinc is concentrated (up to 2% by weight) to levels high enough to be highly toxic to aquatic life and plants.[44] Of particular concern is evidence that some of the compounds that leach from tires into water, contain hormone disruptors and cause liver lesions.[45]
Asymmetric tire
An asymmetric tire is a term used to describe some specific stabilization methods used in cars.
Tire tread
An asymmetric tire may refer to a tire whose tread pattern does not form in line symmetry or point symmetry vis-à-vis its central line, thus having a distinct inside and outside edge. They may be mounted on either side of the vehicle. Since the tread pattern of many ordinary tires do not form symmetry in relation to design or pattern noise, the method of mounting tires is specially prescribed. This type of tires is used in many cases to promote tire performance, braking performance, and turning performance, since tread contact changes according to the change in alignment during travel. Tires may also be directional, where the tread pattern favors operation in one direction. This usually takes the form of v-shaped grooves that help to disperse water from the center to the edge of the tread. Symmetric directional tires can be used on both sides, but once mounted on a rim cannot be moved to the other side, since the tread pattern will be in the wrong direction. This restricts tire rotation. Some directional tires are also asymmetric, in which case there will be specific left and right-handed versions.
Stabilizing belts
An asymmetric tire may refer to a passenger car radial tire in which asymmetric structure stabilizing belts are built. Generally the stabilizing belts give a self-aligning torque when a motor vehicle is running straight ahead as well as when it is cornering. However, the sidewalls of the radial tire are so flexible that there will be a delay in the lateral reaction between the tread of the tire and the rim of its wheel as the vehicle is being steered positively. The lateral force will be transmitted from the front wheel to the rear of the vehicle, which will tend to be steered off course. Whereas the asymmetric belts bring a gradual change in the lateral displacement of the tire tread corresponding to the rim while the cornering load grows. The progressive change will harden the sidewalls to produce an immediate response to steering, which results in safer driving.
See also
Camber thrust
Ground pressure
Tire-pressure gauge
Central Tire Inflation System Cornering force Direct tire pressure monitoring system Dry steering Groove wander
Low-rolling resistance tires Pneumatic trail Relaxation length Skid mark Slip (vehicle dynamics)
Tire-pressure monitoring system Tire label Tire recycling Tramlining
References
1. ^ a b c d Fowler, H. W.; David Crystal (ed.) (2009). A Dictionary of Modern English Usage: The Classic First Edition. Oxford University Press. p. 655. ISBN 978-0-19953534-7. Retrieved 2010-10-23. 2. ^ a b Chisholm, Hugh, ed. (1911). Encyclopædia Britannica, vol. 26. Encyclopædia Britannica. p. 1007. 3. ^ Peters, Pam (2004). The Cambridge Guide to English Usage. Cambridge University Press. p. 553. ISBN 978-0-521-62181-6. 4. ^ Dunlop, John Boyd (2008). Hutchinson Dictionary of Scientific Biography. AccessScience. Retrieved 9 July 2009. 5. ^ a b Werner Obrecht, Jean-Pierre Lambert, Michael Happ, Christiane Oppenheimer-Stix, John Dunn and Ralf Krüger "Rubber, 4. Emulsion Rubbers" in Ullmann's Encyclopedia of Industrial Chemistry, 2012, Wiley-VCH, Weinheim. doi:10.1002/14356007.o23_o01 6. ^ Global Tire Shipments to Reach 1.7 Billion Units by 2015, According to a New Report by Global Industry Analysts, Inc 7. ^ Global tire industry hits $80 billion. | Goliath Business News 8. ^ [1][dead link] 9. ^ Research Report on World's Top 50 Tire Enterprises, 2010-2011 Market Research Report - 02 December 2010 10. ^ KwikFit. "How can I tell when my tyres need changing?". Retrieved 2010-10-23. 11. ^ Jazar, Reza N. (2008). Vehicle dynamics: theory and applications. Springer. p. 11. ISBN 978-0-387-74243-4. Retrieved 2011-03-16. "Inner layers are made of different fabrics, called plies." 12. ^ Jewel, Elizabeth, ed. (2006). The Pocket Oxford Dictionary and Thesaurus. Oxford University Press. p. 722. ISBN 978-0-19-530715-3. Retrieved 2012-03-14. 13. ^ "Demounting and Mounting Procedures". Occupational Safety and Health Administration. 2011. Retrieved 2012-03-14. 14. ^ American Machinist, Volume 40. 1914-04-02. pp. 597–598. Retrieved 2012-03-14. 15. ^ "Bias vs Radial Tires". Mud-throwers.com. Retrieved 2010-10-23. 16. ^ Jones, Thomas H. (1980). "Get things moving with casters, glides, and wheels". Popular Science 216 (5): 148. ISSN 0161-7370. 17. ^ "Thomas Net sources for industrial use 'Semi-Pneumatic Wheels'". Thomasnet.com. Retrieved 2010-10-23. 18. ^ "Car Talk Service Advice: Tire Pressure". Retrieved 2009-01-16. 19. ^ "FEA Chapter III: Tire pressure survey and test results". Retrieved 2009-01-16. 20. ^ "NHTSA test". Retrieved 2009-01-16.
21. ^ Lydall, Ross (2010-05-21). "Taking a ride on Boris's hot wheels hire bikes". London Evening Standard. Retrieved 2010-06-29. 22. ^ "Do Nitrogen-Filled Tires Enhance Fuel-Efficiency?". Scientific American. September 30, 2008. Retrieved 2010-06-29. 23. ^ Tom and Ray Magliozzi (February 2005). "Dear Tom and Ray". CarTalk.com. Retrieved 2010-06-29. 24. ^ Petersen, Gene (October 4, 2007). "Tires - Nitrogen air loss study". Consumer Reports. Retrieved 2011-12-10. "Bottom line: Overall, consumers can use nitrogen and might enjoy the slight improvement in air retention provided, but it's not a substitute for regular inflation checks." 25. ^ "Understanding Retreading". International Tire & Rubber Association. Retrieved 201010-23.[dead link] 26. ^ "Retread Tires". U.S. Environmental Protection Agency. 2008-09-24. Retrieved 201010-23. 27. ^ Brodsky, Harvey. "Federal Government Endorses the Use of Retreaded Tires". Tire Retread Information Bureau. Retrieved 2010-10-23.[dead link] 28. ^ Yokohama 29. ^ SAE. "TKPH application". Retrieved October 7, 2007. 30. ^ Bridgestone. "How to use TKPH". Archived from the original on September 27, 2006. Retrieved October 7, 2007. 31. ^ Goodyear. "New temperature prediction model improves on current TKPH formula". Archived from the original on November 6, 2006. Retrieved October 7, 2007. 32. ^ Brown, Sheldon. "Sheldon Brown on tires". Retrieved 2008-07-01. 33. ^ Markus, Frank. "Racing Fast 'n' Cheap: Ice Racing". Motor Trend. Retrieved 2008-0930. 34. ^ My Kingdom for a Tire, Business Week, April 21, 2008, pp. 46–48 35. ^ My Kingdom for a Tire, Business Week, April 21, 2008, p. 48 36. ^ Federal Aviation Administration, Use of Nitrogen or Other Inert Gas for Tire Inflation in Lieu of Air 37. ^ Hogan, C. Michael (September 1973). "Analysis of highway noise". Journal of Water, Air, & Soil Pollution (Springer Verlag) 2 (3): 387–392. doi:10.1007/BF00159677. ISSN 0049-6979. 38. ^ Lecomte, C (2009). Validation of a Belt Model for Prediction of Hub Forces from a Rolling Tire. Tire Science & Technology 37.2. Retrieved 1 July 2009. 39. ^ ETRTO Standards Manual 2007. Bruxelles, Belgium: ETRTO. 2007. pp. I. 40. ^ "ABC News: Aged Tires Sold as 'New' by Big Retailers". Abcnews.go.com. Retrieved 2010-10-23. 41. ^ 05/09/2008 (2008-05-09). "Aged Tires: A Driving Hazard?". Abcnews.go.com. Retrieved 2010-10-23. 42. ^ Hossain, Mustaque; Nabors, Daniel (Jan–Feb 2005). Testing and evaluation of used automobile tires and recycled tire-derived materials for low-cost crash cushions. 36. Journal of Materials in Civil Engineering. Retrieved 2010-10-23. 43. ^ "Tire-Derived Fuel". U.S. Environmental Protection Agency. Retrieved 2011-12-29. 44. ^ Sullivan, Joseph P. (2006). "An Assessment of Environmental Toxicity and Potential Contamination from Artificial Turf using Shredded or Crumb Rubber" (PDF). Retrieved 2009-06-01.
45. ^ Chalker-Scott, Linda. "The Myth of Rubberized Landscapes" (PDF). Retrieved 200906-01.
External links
Look up inner tube in Wiktionary, the free dictionary. Look up tire or tyre in Wiktionary, the free dictionary. Wikimedia Commons has media related to: Tires
National Highway Traffic Safety Adm "Tire Safety" Brochure U.S. Government tire rating and maintenance site. [show]
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Tire manufacturing
From Wikipedia, the free encyclopedia Jump to: navigation, search This article is written like a personal reflection or essay rather than an encyclopedic description of the subject. Please help improve it by rewriting it in an encyclopedic style. (July 2012) This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (April 2009) Pneumatic tires are manufactured according to relatively standardized processes and machinery, in around 450 tire factories in the world. With over 1 billion tires manufactured worldwide annually, the tire industry is the major consumer of natural rubber. Tire factories start with bulk raw materials such as rubber, carbon black, and chemicals and produce numerous specialized components that are assembled and cured. This article describes the components assembled to make a tire, the various materials used, the manufacturing processes and machinery, and the overall business model.
The tire is an assembly of numerous components that are built up on a drum and then cured in a press under heat and pressure. Heat facilitates a polymerization reaction that crosslinks rubber monomers to create long elastic molecules. These polymers create the elastic quality that permits the tire to be compressed in the area where the tire contacts the road surface and spring back to its original shape under high-frequency cycles. Typical components used in tire assembly are listed below.
Contents
1 Inner liner 2 Body ply 3 Sidewall 4 Beads 5 Apex 6 Belt package 7 Tread 8 Cushion gum 9 Other components 10 Materials 11 Manufacturing process o 11.1 Compounding and mixing o 11.2 Component preparation o 11.3 Tire building o 11.4 Curing o 11.5 Final finish 12 Tire manufacturing companies 13 See also 14 References 15 External links
Inner liner
The inner liner is an extruded halobutyl rubber sheet compounded with additives that result in low air permeability. The inner liner assures that the tire will hold high-pressure air inside, without the air gradually diffusing through the rubber structure.[1]
Body ply
The body ply is a calendered sheet consisting of one layer of rubber, one layer of reinforcing fabric, and a second layer of rubber. The earliest textile used was cotton; later materials include rayon, nylon, polyester, and Kevlar. Passenger tires typically have one or two body plies. Body plies give the tire structure strength. Truck tires, off-road tires, and aircraft tires have progressively more plies. The fabric cords are highly flexible but relatively inelastic.
Sidewall
Sidewalls are non-reinforced extruded profiles with additives to give the sides of the tire good abrasion resistance and environmental resistance. Additives used in sidewall compounds include antioxidants and antiozonants. Sidewall extrusions are nonsymmetrical and provide a thick rubber area to enable molding of raised letters and sidewall ornamentation.
Beads
Beads are bands of high tensile-strength steel wire encased in a rubber compound. Bead wire is coated with special alloys of bronze or brass. Coatings protect the steel from corrosion. Copper in the alloy and sulfur in the rubber cross-link to produce copper sulfide, which improves bonding of the bead to the rubber. Beads are inflexible and inelastic, and provide the mechanical strength to fit the tire to the wheel. Bead rubber includes additives to maximize strength and toughness.
Apex
The apex is a triangular extruded profile that mates against the bead. The apex provides a cushion between the rigid bead and the flexible inner liner and body ply assembly. Alternatively called "filler" (as in the diagram above).
Belt package
Belts are calendered sheets consisting of a layer of rubber, a layer of closely spaced steel cords, and a second layer of rubber. The steel cords are oriented radially in radial tire construction, and at opposing angles in bias tire construction. Belts give the tire strength and dent resistance while allowing it to remain flexible. Passenger tires are usually made with two or three belts.
Tread
The tread is a thick extruded profile that surrounds the tire carcass. Tread compounds include additives to impart wear resistance and traction in addition to environmental resistance. Tread compound development is an exercise in compromise, as hard compounds have long wear characteristics but poor traction whereas soft compounds have good traction but poor wear characteristics.
Cushion gum
Many higher-performing tires include an extruded component between the belt package and the tread to isolate the tread from mechanical wear from the steel belts.
Other components
Tire construction methods vary somewhat in the number and type of components, as well as the compound formulations for each component, according to the tire use and price point. Tire makers continuously introduce new materials and construction methods in order to achieve higher performance at lower cost.
Materials
Natural rubber, or polyisoprene is the basic elastomer used in tire making Styrene-butadiene co-polymer (SBR) is a synthetic rubber which is often substituted in part for natural rubber based on the comparative raw materials cost Polybutadiene is used in combination with other rubbers because of its low heat-buildup properties Halobutyl rubber is used for the tubeless inner liner compounds, because of its low air permeability. The halogen atoms provide a bond with the carcass compounds which are mainly natural rubber. Bromobutyl is superior to chlorobutyl, but is more expensive
Carbon Black, forms a high percentage of the rubber compound. This gives reinforcement and abrasion resistance Silica, used together with carbon black in high performance tires, as a low heat build up reinforcement Sulphur crosslinks the rubber molecules in the vulcanization process Vulcanizing Accelerators are complex organic compounds that speed up the vulcanization Activators assist the vulcanization. The main one is zinc oxide Antioxidants and antiozonants prevent sidewall cracking due to the action of sunlight and ozone Textile fabric reinforces the carcass of the tire
Manufacturing process
Tire plants are traditionally divided into five departments that perform special operations. These usually act as independent factories within a factory. Large tire makers may set up independent factories on a single site, or cluster the factories locally across a region.
Compounding and mixing
SB R rubber compound to with chemicals formulations 1. 2. 3. 4. 5. 6. SB Rubber 100 k.g. carbon 220 50 k.g. zinc oxide 2.5 k.g. static acid 1.5 k.g. accelerator 1.2 k.g. Oil 3.5 k.g.
Compounding is the operation of bringing together all the ingredients required to mix a batch of rubber compound. Each component has a different mix of ingredients according to the properties required for that component. Mixing is the process of applying mechanical work to the ingredients in order to blend them into a homogeneous substance. Internal mixers are often equipped with two counter-rotating rotors in a large housing that shear the rubber charge along with the additives. The mixing is done in three or four stages to incorporate the ingredients in the desired order. The shearing action generates considerable heat, so both rotors and housing are water-cooled to maintain a temperature low enough to assure that vulcanization does not begin. After mixing, the rubber charge is dropped into a chute and fed by an extruding screw into a roller die. Alternatively, the batch can be dropped onto an open rubber mill batchoff system. A mill consists of twin counter-rotating rolls, one serrated, that provide additional mechanical working to the rubber and produce a thick rubber sheet. The sheet is pulled off the rollers in the form of a strip. The strip is cooled, dusted with talc, and laid down into a pallet bin.
The ideal compound at this point would have a highly uniform material dispersion; however in practice there is considerable non-uniformity to the dispersion. This is due to several causes, including hot and cold spots in the mixer housing and rotors, excessive rotor clearance, rotor wear, and poorly circulating flow paths. As a result, there can be a little more carbon black here, and a little less there, along with a few clumps of carbon black elsewhere, that are not well mixed with the rubber or the additives. Mixers are often controlled according to the power integration method, where the current flow to the mixer motor is measured, and the mixing terminated upon reaching a specified total amount of mix energy imparted to the batch.
Component preparation
Components fall into three classes based on manufacturing process: calendering, extrusion, and bead building. The extruder machine consists of a screw and barrel, screw drive, heaters, and a die. The extruder applies two conditions to the compound: heat and pressure. The extruder screw also provides for additional mixing of the compound through the shearing action of the screw. The compound is pushed through a die, after which the extruded profile is vulcanized in a continuous oven, cooled to terminate the vulcanization process, and either rolled up on a spool or cut to length. Tire treads are often extruded with four components in a quadraplex extruder, one with four screws processing four different compounds, usually a base compound, core compound, tread compound, and wing compound. Extrusion is also used for sidewall profiles and inner liners. The calender is a set of multiple large-diameter rolls that squeeze rubber compound into a thin sheet, usually of the order of 2 metres wide. Fabric calenders produce an upper and lower rubber sheet with a layer of fabric in between. Steel calenders do so with steel cords. Calenders are used to produce body plies and belts. A creel room is a facility that houses hundreds of fabric or wire spools that are fed into the calender. Calenders utilize downstream equipment for shearing and splicing calendered components.
Tire building
Tire building is the process of assembling all the components onto a tire building drum. Tirebuilding machines (TBM) can be manually operated or fully automatic. Typical TBM operations include the first-stage operation, where inner liner, body plies, and sidewalls are wrapped around the drum, the beads are placed, and the assembly turned up over the bead. In the second stage operation the belt package and tread are applied and the green tire is inflated and shaped. All components require splicing. Inner liner and body plies are spliced with a square-ended overlap. Tread and sidewall are joined with a skived splice, where the joining ends are bevel-cut. Belts are spliced end to end with no overlap. Splices that are too heavy or non-symmetrical will generate defects in force variation, balance, or bulge parameters. Splices that are too light or
open can lead to visual defects and in some cases tire failure. The final product of the TBM process is called a green tire, where green refers to the uncured state. Pirelli Tire developed a special process called MIRS that uses robots to position and rotate the building drums under stations that apply the various components, usually via extrusion and strip winding methods. This permits the equipment to build different tire sizes in consecutive operations without the need to change tooling or setups. This process is well suited to small volume production with frequent size changes. The largest tire makers have internally developed automated tire-assembly machines in an effort to create competitive advantages in tire construction precision, high production yield, and reduced labor. Nevertheless there is a large base of machine builders who produce tire-building machines.
Curing
Curing is the process of applying pressure to the green tire in a mold in order to give it its final shape, and applying heat energy to stimulate the chemical reaction between the rubber and other materials. In this process the green tire is automatically transferred onto the lower mold bead seat, a rubber bladder is inserted into the green tire, and the mold closes while the bladder inflates. As the mold closes and is locked the bladder pressure increases so as to make the green tire flow into the mold, taking on the tread pattern and sidewall lettering engraved into the mold. The bladder is filled with a recirculating heat transfer medium, such as steam, hot water, or inert gas. Temperatures are in the area of 350 degrees Fahrenheit with pressures around 350 PSI. Passenger tires cure in approximately 15 minutes. At the end of cure the pressure is bled down, the mold opened, and the tire stripped out of the mold. The tire may be placed on a PCI, or postcure inflator, that will hold the tire fully inflated while it cools. There are two generic curing press types, mechanical and hydraulic. Mechanical presses hold the mold closed via toggle linkages, while hydraulic presses use hydraulic oil as the prime mover for machine motion, and lock the mold with a breech-lock mechanism. Hydraulic presses have emerged as the most costeffective because the press structure does not have to withstand the mold-opening pressure and can therefore be relatively lightweight. There are two generic mold types, two-piece molds and segmental molds. Large off-road tires are often cured in ovens with cure times approaching 24 hours.
Final finish
After the tire has been cured, there are several additional operations. Tire uniformity measurement is a test where the tire is automatically mounted on wheel halves, inflated, run against a simulated road surface, and measured for force variation. Tire balance measurement is a test where the tire is automatically placed on wheel halves, rotated at a high speed and measured for imbalance. Large commercial truck/bus tires, as well as some passenger and light truck tires, are inspected by X-ray machines that can penetrate the rubber to analyze the steel cord structure.
In the final step, tires are inspected by human eyes for numerous visual defects such as incomplete mold fill, exposed cords, blisters, blemishes, and others.
Tire manufacturing companies
For a list of tire companies, List of tire companies.
See also
Retread
References
1. ^ http://www.goodyeartires.com/about/diversity/how_built.html
External links
The Tire Society
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Magyar This page was last modified on 26 July 2012 at 11:06. Text is available under the Creative Commons Attribution-ShareAlike License; additional terms may apply. See Terms of use for details. Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc., a non-profit organization. Contact us Privacy policy About Wikipedia Disclaimers Mobile view
