Tire
Overview

A tire or tyre (in Commonwealth Nations such as UK, Australia, and others) is a ring-shaped covering that fits around a wheel rim
Rim (wheel)
The rim of a wheel is the outer circular design of the metal on which the inside edge of the tire is mounted on vehicles such as automobiles. For example, on a bicycle wheel the rim is a large hoop attached to the outer ends of the spokes of the wheel that holds the tire and tube.In the 1st...

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
Synthetic rubber
Synthetic rubber is is any type of artificial elastomer, invariably a polymer. An elastomer is a material with the mechanical property that it can undergo much more elastic deformation under stress than most materials and still return to its previous size without permanent deformation...

, natural rubber, fabric and wire, along with other compound chemicals.
Encyclopedia
A tire or tyre (in Commonwealth Nations such as UK, Australia, and others) is a ring-shaped covering that fits around a wheel rim
Rim (wheel)
The rim of a wheel is the outer circular design of the metal on which the inside edge of the tire is mounted on vehicles such as automobiles. For example, on a bicycle wheel the rim is a large hoop attached to the outer ends of the spokes of the wheel that holds the tire and tube.In the 1st...

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
Synthetic rubber
Synthetic rubber is is any type of artificial elastomer, invariably a polymer. An elastomer is a material with the mechanical property that it can undergo much more elastic deformation under stress than most materials and still return to its previous size without permanent deformation...

, natural rubber, fabric and wire, along with other compound chemicals. They consist of a tread and a body. The tread provides traction
Traction (engineering)
Traction refers to the maximum frictional force that can be produced between surfaces without slipping.The units of traction are those of force, or if expressed as a coefficient of traction a ratio.-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 in order 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 bicycle
Bicycle
A bicycle, also known as a bike, pushbike or cycle, is a human-powered, pedal-driven, single-track vehicle, having two wheels attached to a frame, one behind the other. A person who rides a bicycle is called a cyclist, or bicyclist....

s, motorcycles, cars
CARS
Cars, or automobiles, motor cars, are wheeled motor vehicles used for transporting passengers.Cars or CARS may also refer to:-Entertainment:* Cars , a Disney/Pixar film series...

, truck
Truck
A truck or lorry is a motor vehicle designed to transport cargo. Trucks vary greatly in size, power, and configuration, with the smallest being mechanically similar to an automobile...

s, earthmovers, and aircraft
Aircraft
An aircraft is a vehicle that is able to fly by gaining support from the air, or, in general, the atmosphere of a planet. An aircraft counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines.Although...

.

## Etymology and spelling

The Oxford English Dictionary
Oxford English Dictionary
The Oxford English Dictionary , published by the Oxford University Press, is the self-styled premier dictionary of the English language. Two fully bound print editions of the OED have been published under its current name, in 1928 and 1989. The first edition was published in twelve volumes , and...

suggests that the word derives from "attire", while other sources suggest a connection with the verb "to tie". From the 15th to the 17th centuries the spellings tire and tyre were used without distinction; but by 1700 tyre had become obsolete and tire remained as the settled spelling. 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
The Times
The Times is a British daily national newspaper, first published in London in 1785 under the title The Daily Universal Register . The Times and its sister paper The Sunday Times are published by Times Newspapers Limited, a subsidiary since 1981 of News International...

newspaper in Britain was still using tire as late as 1905. The 1911 edition of the Encyclopædia Britannica
Encyclopædia Britannica Eleventh Edition
The Encyclopædia Britannica Eleventh Edition is a 29-volume reference work, an edition of the Encyclopædia Britannica. It was developed during the encyclopaedia's transition from a British to an American publication. Some of its articles were written by the best-known scholars of the time...

states that "[t]he spelling 'tyre' is not now accepted by the best English authorities, and is unrecognized in the US", 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".
However, over the course of the 20th century tyre became established as the standard British spelling.

### Iron tires

The earliest tires were bands of iron
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...

(later steel
Steel
Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...

), placed on wooden wheel
Wheel
A wheel is a device that allows heavy objects to be moved easily through rotating on an axle through its center, facilitating movement or transportation while supporting a load, or performing labor in machines. Common examples found in transport applications. A wheel, together with an axle,...

s, used on cart
Cart
A cart is a vehicle designed for transport, using two wheels and normally pulled by one or a pair of draught animals. A handcart is pulled or pushed by one or more people...

s and wagon
Wagon
A wagon is a heavy four-wheeled vehicle pulled by draught animals; it was formerly often called a wain, and if low and sideless may be called a dray, trolley or float....

s. The tire would be heated in a forge
Forge
A forge is a hearth used for forging. The term "forge" can also refer to the workplace of a smith or a blacksmith, although the term smithy is then more commonly used.The basic smithy contains a forge, also known as a hearth, for heating metals...

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
Wheelwright
A wheelwright is a person who builds or repairs wheels. The word is the combination of "wheel" and the archaic word "wright", which comes from the Old English word "wryhta", meaning a worker or maker...

, 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. So these tires were able to sustain very heavy pressures. The word "tire" thus emerged as a variant spelling to refer to the metal bands used to tie wheels.

### Rubber tires

The first practical pneumatic tire was made by John Boyd Dunlop
John Boyd Dunlop
John Boyd Dunlop was a Scottish inventor. He was one of the founders of the rubber company that bore his name, Dunlop Pneumatic Tyre Company....

while working as a veterinarian in May Street, Belfast, in 1887 for his son's bicycle
Bicycle
A bicycle, also known as a bike, pushbike or cycle, is a human-powered, pedal-driven, single-track vehicle, having two wheels attached to a frame, one behind the other. A person who rides a bicycle is called a cyclist, or bicyclist....

, 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
Robert William Thomson
Robert William Thomson , from Stonehaven, Scotland, was the original inventor of the pneumatic tyre.-Biography:...

). Dunlop is credited with "realizing rubber could withstand the wear and tear of being a tire while retaining its resilience".

Pneumatic tires are made of a flexible elastomer
Elastomer
An elastomer is a polymer with the property of viscoelasticity , generally having notably low Young's modulus and high yield strain compared with other materials. The term, which is derived from elastic polymer, is often used interchangeably with the term rubber, although the latter is preferred...

material, such as rubber, with reinforcing materials such as fabric and wire. Tire companies were first started in the early 20th century, and grew in tandem with the auto industry. Today, over 1 billion tires are produced annually, in over 400 tire factories, with the three top tire makers commanding a 60% global market share.

### Chronology

• 1846 – Robert William Thomson
Robert William Thomson
Robert William Thomson , from Stonehaven, Scotland, was the original inventor of the pneumatic tyre.-Biography:...

invents and patents the pneumatic tire
• 1880s – John Boyd Dunlop
John Boyd Dunlop
John Boyd Dunlop was a Scottish inventor. He was one of the founders of the rubber company that bore his name, Dunlop Pneumatic Tyre Company....

begins taping pneumatic tires to bicycle
Bicycle
A bicycle, also known as a bike, pushbike or cycle, is a human-powered, pedal-driven, single-track vehicle, having two wheels attached to a frame, one behind the other. A person who rides a bicycle is called a cyclist, or bicyclist....

wheels
• 1888 – First commercial pneumatic bicycle tire produced by Dunlop
• 1889 – Dunlop patents the pneumatic tire in the UK
Gustave Adolphe Clément-Bayard was a French entrepreneur...

sees a Dunlop pneumatic tire in London and acquires the French manufacturing rights for 50,000 francs
• 1890 – Dunlop, and William Harvey Du Cros begin production of pneumatic tires in Ireland
Ireland
Ireland is an island to the northwest of continental Europe. It is the third-largest island in Europe and the twentieth-largest island on Earth...

; thickened beads, wire retainers, and shaped rims make taping tires to rims unnecessary.
• 1890 – Bartlett Clincher rim introduced
• 1891 – Dunlop's patent invalidated in favor of Thomson’s
• 1891 – The Michelin
Michelin
Michelin is a tyre manufacturer based in Clermont-Ferrand in the Auvergne région of France. It is one of the two largest tyre manufacturers in the world along with Bridgestone. In addition to the Michelin brand, it also owns the BFGoodrich, Kleber, Riken, Kormoran and Uniroyal tyre brands...

brothers patent a removable pneumatic tire, used by Charles Terront
Charles Terront
Charles Terront was the first major French cycling star. He won sprint, middle distance and endurance events in Europe and the United States. In September 1891 he won the first Paris–Brest–Paris cycle race, which at was more than double the length of any previous event...

to win the world's first long distance cycle race, Paris–Brest–Paris.
• 1892 – Beaded edge tires introduced in the U.S.
• 1893 – Cotton reinforcing cords have appeared
• 1894 – E.J. Pennington invents the first balloon tire
• 1895 – Michelin introduces pneumatic automobile tires; André Michelin
André Michelin
André Jules Michelin was aFrench industrialist who, with his brother Édouard , founded the Michelin Tyre Company in 1888 in the French city of Clermont-Ferrand.In 1900, André Michelin published the first Michelin Guide, the purpose of which was to promote tourism by car,...

uses corded tires in Paris-Bordeaux-Paris rally: by 1897, they are standard racing tires
The Schrader valve is a brand of pneumatic tire valve used on virtually every motor vehicle in the world today. The Schrader company, for which it was named, was founded in 1844 by August Schrader...

stem patented
• 1900 – Cord tires introduced by Palmer (England) and BFGoodrich (U.S.)
• 1903 – Paul W. Litchfield of the Goodyear Tire Company granted patent for the first tubeless tire
Tubeless tire
Tubeless tires are pneumatic tires that do not require a separate inner tube. Unlike traditional pneumatic tires which use a separate inner tube, tubeless tires have continuous ribs molded integrally into the bead of the tire so that they are forced by the pressure of the air inside the tire to...

, which was introduced in 1954 by Goodyear on Packard
Packard
Packard was an American luxury-type automobile marque built by the Packard Motor Car Company of Detroit, Michigan, and later by the Studebaker-Packard Corporation of South Bend, Indiana...

s) (Litchfield would go on to become Goodyear's president and board chairman.)
• 1904 – Goodyear and Firestone start producing cord-reinforced tires
• 1904 – Mountable rims introduced, allowing drivers to fix their own flats
• 1906 – First pneumatic aircraft tire
• 1908 – Frank Seiberling
Frank Seiberling
Franklin Augustus Seiberling was an American inventor and founder. He is most famous for founding the Goodyear Tire and Rubber Company and the Seiberling Rubber Company...

invents grooved tires with improved road traction
• 1900s  – Tire companies experiment with adding leather, wood, and steel to improve durability
• 1910 – Silvertown Rubber Company (London) adds carbon black
Carbon black
Carbon black is a material produced by the incomplete combustion of heavy petroleum products such as FCC tar, coal tar, ethylene cracking tar, and a small amount from vegetable oil. Carbon black is a form of amorphous carbon that has a high surface-area-to-volume ratio, although its...

to white rubber, increasing durability: now universal
• 1919 – Goodyear and Dunlop announce pneumatic truck tires
• 1923  – First balloon tire, named for larger cross section and lower pressure, introduced by Firestone: debut on the first Chrysler
Chrysler
Chrysler Group LLC is a multinational automaker headquartered in Auburn Hills, Michigan, USA. Chrysler was first organized as the Chrysler Corporation in 1925....

, the 70, in 1924
• 1929  – Solid automobile tires cease to be used
• 1937 – BFGoodrich introduces the first commercial synthetic rubber
Synthetic rubber
Synthetic rubber is is any type of artificial elastomer, invariably a polymer. An elastomer is a material with the mechanical property that it can undergo much more elastic deformation under stress than most materials and still return to its previous size without permanent deformation...

tire
• 1938 – Goodyear introduces the rayon
Rayon
Rayon is a manufactured regenerated cellulose fiber. Because it is produced from naturally occurring polymers, it is neither a truly synthetic fiber nor a natural fiber; it is a semi-synthetic or artificial fiber. Rayon is known by the names viscose rayon and art silk in the textile industry...

cord tire
• 1946 – Michelin introduces the radial tire
A radial tire is a particular design of automotive tire . In this design, the cord plies are arranged at 90 degrees to the direction of travel, or radially ....

• 1947 – Goodyear introduces first nylon
Nylon
Nylon is a generic designation for a family of synthetic polymers known generically as polyamides, first produced on February 28, 1935, by Wallace Carothers at DuPont's research facility at the DuPont Experimental Station...

belted tires
• 1947 – BFGoodrich announces the tubeless tire
• 1963 – Use of polyester
Polyester
Polyester is a category of polymers which contain the ester functional group in their main chain. Although there are many polyesters, the term "polyester" as a specific material most commonly refers to polyethylene terephthalate...

cord introduced by Goodyear
• 1965 – Armstrong Rubber introduces the bias belted fiberglass tire
• 1967 – Poly/glass tires introduced by Firestone and Goodyear
• 1968 – United States Department of Transportation
United States Department of Transportation
The United States Department of Transportation is a federal Cabinet department of the United States government concerned with transportation. It was established by an act of Congress on October 15, 1966, and began operation on April 1, 1967...

(DOT) numbers required on new tires in U.S.
• 1974 – Pirelli
Pirelli
Pirelli & C. SpA is a diverse multinational company based in Milan, Italy. The company, the world’s fifth largest tyre manufacturer, is present in over 160 countries, has 20 manufacturing sites around the world and a network of around 10,000 distributors and retailers.Founded in Milan in 1872,...

introduces the wide (low aspect ratio
Aspect ratio
The aspect ratio of a shape is the ratio of its longer dimension to its shorter dimension. It may be applied to two characteristic dimensions of a three-dimensional shape, such as the ratio of the longest and shortest axis, or for symmetrical objects that are described by just two measurements,...

• 1975 – Michelin
Michelin
Michelin is a tyre manufacturer based in Clermont-Ferrand in the Auvergne région of France. It is one of the two largest tyre manufacturers in the world along with Bridgestone. In addition to the Michelin brand, it also owns the BFGoodrich, Kleber, Riken, Kormoran and Uniroyal tyre brands...

very first American-built radial passenger tire
• 1992 – Michelin introduces the first durable silica-filled tire, also known as "green tires".
• 1998 – Michelin develops tire that’s vertically anchored and unseatable, allowing it to run flat after a loss of pressure,
• 2000 – Firestone
Firestone Tire and Rubber Company
The Firestone Tire and Rubber Company is an American tire company founded by Harvey Firestone in 1900 to supply pneumatic tires for wagons, buggies, and other forms of wheeled transportation common in the era. Firestone soon saw the huge potential for marketing tires for automobiles. The company...

recalls tires after Congressional hearings into rollover accidents of Ford Explorer
Ford Explorer
The Ford Explorer is a sport-utility vehicle sold in North America and built by the Ford Motor Company since 1990, as a replacement for the smaller but related Ford Bronco II. It is manufactured in Chicago, Illinois...

s in Firestone and Ford tire controversy
Firestone and Ford tire controversy
The Firestone and Ford tire controversy was a period of unusually high tire failures on some Ford vehicles.-Problem detection:In May 2000, the U.S. National Highway Traffic Safety Administration contacted Ford and Firestone about the high incidence of tire failure on Ford Explorers, Mercury...

For a list of tire companies and the dates they were established, see List of Tire Companies.

## Manufacturing

Pneumatic tires are manufactured according to relatively standardized processes and machinery, in around 450 tire factories in the world. Over 1 billion tires are manufactured annually, making the tire industry the majority consumer of natural rubber. In 2015 1.72 billion tires are expected to be sold globally. 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.

In 2004, $80 billion of tires were sold worldwide, in 2010 it was$140 billion.

The top five tire manufacturing companies by revenue are Bridgestone
Bridgestone
The is a multinational rubber conglomerate founded in 1931 by in the city of Kurume, Fukuoka, Japan. The name Bridgestone comes from a calque translation and transposition of ishibashi, meaning "stone bridge" in Japanese....

, Michelin
Michelin
Michelin is a tyre manufacturer based in Clermont-Ferrand in the Auvergne région of France. It is one of the two largest tyre manufacturers in the world along with Bridgestone. In addition to the Michelin brand, it also owns the BFGoodrich, Kleber, Riken, Kormoran and Uniroyal tyre brands...

, Goodyear
Goodyear Tire and Rubber Company
The Goodyear Tire & Rubber Company was founded in 1898 by Frank Seiberling. Goodyear manufactures tires for automobiles, commercial trucks, light trucks, SUVs, race cars, airplanes, farm equipment and heavy earth-mover machinery....

, Continental AG
Continental AG
Continental AG, internally often called Conti for short, is a worldwide leading German manufacturer of tires, brake systems, vehicle stability control systems, engine injection systems, tachographs and other parts for the automotive and transport industries. The company is based in Hanover, Germany...

and Pirelli
Pirelli
Pirelli & C. SpA is a diverse multinational company based in Milan, Italy. The company, the world’s fifth largest tyre manufacturer, is present in over 160 countries, has 20 manufacturing sites around the world and a network of around 10,000 distributors and retailers.Founded in Milan in 1872,...

.

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
Contact patch
Contact patch is the portion of a vehicle's tire that is in actual contact with the road surface. It is most commonly used in the discussion of pneumatic tires, , where the term is strictly used to describe the portion of the tire’s tread that touches the road surface...

. 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 in order 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 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. These forces are described as Force Variation.

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. 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. This results in a smoother ride in different types of weather.

#### 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
Shear stress
A shear stress, denoted \tau\, , is defined as the component of stress coplanar with a material cross section. Shear stress arises from the force vector component parallel to the cross section...

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 mm and are deemed "worn out" at that point.

The bead is that part of the tire that contacts the rim
Rim (wheel)
The rim of a wheel is the outer circular design of the metal on which the inside edge of the tire is mounted on vehicles such as automobiles. For example, on a bicycle wheel the rim is a large hoop attached to the outer ends of the spokes of the wheel that holds the tire and tube.In the 1st...

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

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 in order 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
Whitewall tire
Whitewall tires or white sidewall tires are tires having a stripe or entire sidewall of white rubber.-Background:Early automobile tires were made entirely of natural white rubber. However, the white rubber did not offer sufficient traction and endurance, so carbon black was added to the rubber...

.

### 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 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.

### Rim

Tires are mounted to wheel
Wheel
A wheel is a device that allows heavy objects to be moved easily through rotating on an axle through its center, facilitating movement or transportation while supporting a load, or performing labor in machines. Common examples found in transport applications. A wheel, together with an axle,...

s that bolt to the hub. The beads of the tire are held on the wheel's rim
Rim (wheel)
The rim of a wheel is the outer circular design of the metal on which the inside edge of the tire is mounted on vehicles such as automobiles. For example, on a bicycle wheel the rim is a large hoop attached to the outer ends of the spokes of the wheel that holds the tire and tube.In the 1st...

largely by the internal tire force from the air pressure. Automotive wheels are typically made from pressed and welded steel, or a composite of lightweight metal alloy
Alloy
An alloy is a mixture or metallic solid solution composed of two or more elements. Complete solid solution alloys give single solid phase microstructure, while partial solutions give two or more phases that may or may not be homogeneous in distribution, depending on thermal history...

s, such as aluminum or magnesium. These alloy wheel
Alloy wheel
Alloy wheels are automobile wheels which are made from an alloy of aluminium or magnesium. They are typically lighter for the same strength...

s may be either cast
Casting
In metalworking, casting involves pouring liquid metal into a mold, which contains a hollow cavity of the desired shape, and then allowing it to cool and solidify. The solidified part is also known as a casting, which is ejected or broken out of the mold to complete the process...

or forged
Forging
Forging is a manufacturing process involving the shaping of metal using localized compressive forces. Forging is often classified according to the temperature at which it is performed: '"cold," "warm," or "hot" forging. Forged parts can range in weight from less than a kilogram to 580 metric tons...

. A decorative hubcap
Hubcap
A hubcap, wheel cover or wheel trim is a decorative disk on an automobile wheel that covers at least a central portion of the wheel. Cars with stamped steel wheels often use a full wheel cover that conceals the entire wheel. Cars with alloy wheels or styled steel wheels generally use smaller...

and trim ring may be placed over the wheel.

### Inner tube

Almost all 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
Torus
In geometry, a torus is a surface of revolution generated by revolving a circle in three dimensional space about an axis coplanar with the circle...

-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
Swim ring
A swim ring is a toroid-shaped inflatable water toy....

), tubing (recreation)
Tubing (recreation)
Tubing is a recreational activity where an individual rides on top of an inner tube, either on water, snow, or through the air. The tubes themselves are also known as "donuts" or "biscuits" due to their shape.-Water:Tubing on water generally consists of two forms: towed and free-floating, also...

, sledding
Sledding
Sledding , sledging , sleding or tobogganing is a common activity in wintry areas, similar to sliding, but in a prone or seated position requiring a device or vehicle generically known in the US as a sled or in other countries as a sledge or toboggan...

, and skitching
Skitching
Skitching is the act of hitching a ride by holding on to a motor vehicle while riding on a skateboard or roller skates...

. 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.

### Valve stem

The valve stem is a tube made of metal or rubber, through which the tire is inflated, with a check valve
Check valve
A check valve, clack valve, non-return valve or one-way valve is a mechanical device, a valve, which normally allows fluid to flow through it in only one direction....

The Schrader valve is a brand of pneumatic tire valve used on virtually every motor vehicle in the world today. The Schrader company, for which it was named, was founded in 1844 by August Schrader...

on automobiles and most bicycle tires, or a Presta valve
Presta valve
The Presta valve is a valve commonly found in high pressure road style and many mountain bicycle inner tubes. It comprises an outer valve stem and an inner valve body...

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.

### 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.

### 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. These tires often come as a complete assembly with the wheel and even integral ball bearing
Ball bearing
A ball bearing is a type of rolling-element bearing that uses balls to maintain the separation between the bearing races.The purpose of a ball bearing is to reduce rotational friction and support radial and axial loads. It achieves this by using at least two races to contain the balls and transmit...

s. They are used on lawn mower
Lawn mower
A lawn mower is a machine that uses a revolving blade or blades to cut a lawn at an even length.Lawn mowers employing a blade that rotates about a vertical axis are known as rotary mowers, while those employing a blade assembly that rotates about a horizontal axis are known as cylinder or reel...

s, wheelchair
Wheelchair
A wheelchair is a chair with wheels, designed to be a replacement for walking. The device comes in variations where it is propelled by motors or by the seated occupant turning the rear wheels by hand. Often there are handles behind the seat for someone else to do the pushing...

s, and wheelbarrow
Wheelbarrow
A wheelbarrow is a small hand-propelled vehicle, usually with just one wheel, designed to be pushed and guided by a single person using two handles to the rear, or by a sail to push the ancient wheelbarrow by wind. The term "wheelbarrow" is made of two words: "wheel" and "barrow." "Barrow" is a...

s. They can also be rugged, typically used in industrial applications, and are designed to not pull off their rim
Rim (wheel)
The rim of a wheel is the outer circular design of the metal on which the inside edge of the tire is mounted on vehicles such as automobiles. For example, on a bicycle wheel the rim is a large hoop attached to the outer ends of the spokes of the wheel that holds the tire and tube.In the 1st...

under use.

Tires that are hollow but are not pressurized have also been designed for automotive use, such as the Tweel
Tweel
The Tweel is an experimental tire design developed by the French tire company Michelin. The tire uses no air, and therefore cannot burst or become flat...

(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
Polyurethane
A polyurethane is any polymer composed of a chain of organic units joined by carbamate links. Polyurethane polymers are formed through step-growth polymerization, by reacting a monomer with another monomer in the presence of a catalyst.Polyurethanes are...

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.

### 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. 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. If tire pressure is too low, the tire contact patch is changed more than if it were over-inflated. This decreases 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.

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
Tire code
Automobile tires are described by an alphanumeric tire code or tyre code , which is generally molded into the sidewall of the tire. This code specifies the dimensions of the tire, and some of its key limitations, such as load-bearing ability, and maximum speed...

.

### 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 mph (44.3 to 83.1 ). For a table of speed ratings, see tire code
Tire code
Automobile tires are described by an alphanumeric tire code or tyre code , which is generally molded into the sidewall of the tire. This code specifies the dimensions of the tire, and some of its key limitations, such as load-bearing ability, and maximum speed...

.

Replacing a tire on a vehicle with one with a lower speed rating than originally specified by the vehicle manufacturer may render the insurance invalid.

### 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 (804.7 km) or more per day carrying heavy loads require special specifications.

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
Front-wheel drive
Front-wheel drive is a form of engine/transmission layout used in motor vehicles, where the engine drives the front wheels only. Most modern front-wheel drive vehicles feature a transverse engine, rather than the conventional longitudinal engine arrangement generally found in rear-wheel drive and...

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 front-to-rear, in order to even out the wear, thereby extending the life of the tire.

### 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 quite substantial if left uncorrected.

Wheel alignment is the procedure for checking and correcting this condition through adjustment of camber
Camber angle
thumb|100px|From the front of the car, a right wheel with a negative camber angleCamber angle is the angle made by the wheels of a vehicle; specifically, it is the angle between the vertical axis of the wheels used for steering and the vertical axis of the vehicle when viewed from the front or...

, caster
Caster angle
thumb|250px|θ is the caster angle, the red line is the pivot line, and the grey area is the tire.Caster angle or castor angle is the angular displacement from the vertical axis of the suspension of a steered wheel in a car, bicycle or other vehicle, measured in the longitudinal direction...

and toe
Toe (automotive)
In automotive engineering, toe, also known as tracking, is the symmetric angle that each wheel makes with the longitudinal axis of the vehicle, as a function of static geometry, and kinematic and compliant effects. This can be contrasted with steer, which is the antisymmetric angle, i.e. both...

angles. These settings also affect the handling characteristics of the vehicle.

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. 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, in order 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. 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.

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
Phenomenon
A phenomenon , plural phenomena, is any observable occurrence. Phenomena are often, but not always, understood as 'appearances' or 'experiences'...

. Many of the details are modeled in Pacejka's Magic Formula. Some are explained below.

### Balance

When a wheel and tire rotate, they exert a centrifugal force
Centrifugal force
Centrifugal force can generally be any force directed outward relative to some origin. More particularly, in classical mechanics, the centrifugal force is an outward force which arises when describing the motion of objects in a rotating reference frame...

on the axle that depends on the location of their center of mass
Center of mass
In physics, the center of mass or barycenter of a system is the average location of all of its mass. In the case of a rigid body, the position of the center of mass is fixed in relation to the body...

and the orientation of their moment of inertia
Moment of inertia
In classical mechanics, moment of inertia, also called mass moment of inertia, rotational inertia, polar moment of inertia of mass, or the angular mass, is a measure of an object's resistance to changes to its rotation. It is the inertia of a rotating body with respect to its rotation...

. 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.

### 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
Camber
Camber may refer to a variety of curvatures and angles:* Camber angle, the angle made by the wheels of a vehicle* Camber thrust in bike technology* In the steel industry, the concavity of rolls...

angle and finite contact patch.

### Centrifugal growth

A tire rotating at higher speeds tends to develop a larger diameter, due to centrifugal force
Centrifugal force
Centrifugal force can generally be any force directed outward relative to some origin. More particularly, in classical mechanics, the centrifugal force is an outward force which arises when describing the motion of objects in a rotating reference frame...

s that force the tread rubber away from the axis of rotation. This may cause speedometer error. As the tire diameter
Diameter
In geometry, a diameter of a circle is any straight line segment that passes through the center of the circle and whose endpoints are on the circle. The diameters are the longest chords of the circle...

grows, the tire width decreases. This centrifugal growth can cause rubbing of the tire against the vehicle at high speeds. Motorcycle
Motorcycle
A motorcycle is a single-track, two-wheeled motor vehicle. Motorcycles vary considerably depending on the task for which they are designed, such as long distance travel, navigating congested urban traffic, cruising, sport and racing, or off-road conditions.Motorcycles are one of the most...

tires are often designed with reinforcements aimed at minimizing centrifugal growth.

### 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

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

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 compressed 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
Tire Uniformity refers to the dynamic mechanical properties of pneumatic tires as strictly defined by a set of measurement standards and test conditions accepted by global tire and car makers. These measurement standards include the parameters of radial force variation, lateral force variation,...

. Tire uniformity is characterized by radial force variation
Tires provide for steering, traction, braking, and load support by transmitting forces between the vehicle and the road. Radial Force Variation is a property of a tire that characterizes its dynamic behavior of these forces...

(RFV), lateral force variation
Lateral Force Variation
Tires provide for steering, traction, braking, and load support by transmitting forces between the vehicle and the road. Lateral Force Variation is a property of a tire that characterizes its dynamic behavior of these forces...

(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 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

Pneumatic trail
Pneumatic trail
Pneumatic trail or trail of the tire is a trail-like effect generated by compliant tires rolling on a hard surface and subject to side loads, as in a turn...

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
Cornering force
Cornering force or side force is the lateral force produced by a vehicle tire during cornering.Cornering force is generated by tire slip and is proportional to slip angle at low slip angles. The rate at which cornering force builds up is described by relaxation length...

of side-slip
Slip angle
In vehicle dynamics, 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...

occurs behind the geometric center of the contact patch
Contact patch
Contact patch is the portion of a vehicle's tire that is in actual contact with the road surface. It is most commonly used in the discussion of pneumatic tires, , where the term is strictly used to describe the portion of the tire’s tread that touches the road surface...

.

### 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

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 in order to improve fuel economy
Fuel economy
Fuel economy may refer to:*Fuel economy in automobiles, refers to the fuel efficiency relationship between distance traveled by an automobile and the amount of fuel consumed*Fuel efficiency in general...

in cars and especially trucks, where rolling resistance accounts for a high proportion of fuel consumption.

Pneumatic tires also has 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 wheelchair
Wheelchair
A wheelchair is a chair with wheels, designed to be a replacement for walking. The device comes in variations where it is propelled by motors or by the seated occupant turning the rear wheels by hand. Often there are handles behind the seat for someone else to do the pushing...

s or baby buggies fitted with either type so long as the terrain has a significant roughness in relation to the wheel diameter.

### Self aligning torque

Self aligning torque, also known as the aligning torque, SAT or Mz, is the torque
Torque
Torque, moment or moment of force , is the tendency of a force to rotate an object about an axis, fulcrum, or pivot. Just as a force is a push or a pull, a torque can be thought of as a twist....

that a tire creates as it rolls along that tends to steer it, i.e. rotate it around its vertical axis.

### 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.

The work load of a tire is monitored so that it is not put under undue stress, which may lead to its premature failure. Work load is measured
Measurement
Measurement is the process or the result of determining the ratio of a physical quantity, such as a length, time, temperature etc., to a unit of measurement, such as the metre, second or degree Celsius...

in ton
Ton
The ton is a unit of measure. It has a long history and has acquired a number of meanings and uses over the years. It is used principally as a unit of weight, and as a unit of volume. It can also be used as a measure of energy, for truck classification, or as a colloquial term.It is derived from...

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. 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
Ton
The ton is a unit of measure. It has a long history and has acquired a number of meanings and uses over the years. It is used principally as a unit of weight, and as a unit of volume. It can also be used as a measure of energy, for truck classification, or as a colloquial term.It is derived from...

mile per hour (TMPH).

There are several types of abnormal tread wear. Poor wheel alignment
Wheel alignment
Wheel alignment sometimes referred to as tracking, is part of standard automobile maintenance that consists of adjusting the angles of the wheels so that they are set to the car maker's specification. The purpose of these adjustments is to reduce tire wear, and to ensure that vehicle travel is...

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 under-inflated as a result. 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
Traction
- Engineering :*Forces:** Traction , adhesive friction or force in the context of vehicle** Traction vector, in mechanics, the force per unit area on a surface, including normal and shear components...

, 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
Hydroplaning
Hydroplaning and hydroplane may refer to:* Aquaplaning, also known as hydroplaning, a loss of steering or braking control when a layer of water prevents direct contact between tires and the road, runway, or other surface....

. 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.

### DOT code

In the United States, the DOT Code is an alphanumeric
Alphanumeric
Alphanumeric is a combination of alphabetic and numeric characters, and is used to describe the collection of Latin letters and Arabic digits or a text constructed from this collection. There are either 36 or 62 alphanumeric characters. The alphanumeric character set consists of the numbers 0 to...

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
United States Department of Transportation
The United States Department of Transportation is a federal Cabinet department of the United States government concerned with transportation. It was established by an act of Congress on October 15, 1966, and began operation on April 1, 1967...

. The DOT Code is useful in identifying tires in a product recall
Product recall
A product recall is a request to return to the maker a batch or an entire production run of a product, usually due to the discovery of safety issues. The recall is an effort to limit liability for corporate negligence and to improve or avoid damage to publicity...

.

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 the year 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.

## 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 OTR tires.

#### 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. 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

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).

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 regulated in most countries, and even prohibited in some locales due to the increased road wear caused by studs. Typically, studs are never used on heavier vehicles. Studded tires are used in the upper tier classes of ice racing
Ice racing
Ice racing is a form of racing that uses cars, motorcycles, snowmobiles, All-terrain vehicles, or other motorized vehicles. Ice racing takes place on frozen lakes or rivers, or on carefully groomed frozen lots...

and rallying
Rallying
Rallying, also known as rally racing, is a form of auto racing that takes place on public or private roads with modified production or specially built road-legal cars...

.

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 specialty 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 'snowplow' the snow in front. 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 almost 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. All-Season 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 SUV
Sport utility vehicle
A sport utility vehicle is a generic marketing term for a vehicle similar to a station wagon, but built on a light-truck chassis. It is usually equipped with four-wheel drive for on- or off-road ability, and with some pretension or ability to be used as an off-road vehicle. Not all four-wheel...

s and light truck
Light truck
Light truck or light duty truck is a U.S. classification for trucks or truck-based vehicles with a payload capacity of less than 4,000 pounds...

s. 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

Some vehicles carry a spare tire, already mounted on a wheel, to be used in the event of flat tire or blowout
Blowout (tire)
A blowout is a rapid loss of inflation pressure of a pneumatic tire leading to an explosion. The primary cause for this is encountering an object that cuts or tears the structural components of the tire to the point where the structure is incapable of containing the pressurized air, with the...

. 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 (26.8 m/s).

#### Run-flat

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 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 sub-categorized 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 mm-295 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 200 pounds (90.7 kg) per axle, this enables vehicles using these to improve fuel economy.

The OTR tire classification includes 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. 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.

### 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
Soil compaction
In Geotechnical engineering, soil compaction is the process in which a stress applied to a soil causes densification as air is displaced from the pores between the soil grains. When stress is applied that causes densification due to water being displaced from between the soil grains then...

is a concern, featuring large footprints at low inflation pressures.

### Racing

Racing tires are highly specialized according to vehicle and race track
Race track
A race track is a purpose-built facility for racing of animals , automobiles, motorcycles or athletes. A race track may also feature grandstands or concourses. Some motorsport tracks are called speedways.A racetrack is a permanent facility or building...

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
Formula One
Formula One, also known as Formula 1 or F1 and referred to officially as the FIA Formula One World Championship, is the highest class of single seater auto racing sanctioned by the Fédération Internationale de l'Automobile . The "formula" designation in the name refers to a set of rules with which...

, IndyCar
IndyCar Series
The IZOD IndyCar Series is the premier level of American open wheel racing. The current championship, founded by Indianapolis Motor Speedway owner Tony George, began in 1996 as a competitor to CART known as the Indy Racing League . Citing CART's increasing reliance on expensive machinery and...

, NASCAR
NASCAR
The National Association for Stock Car Auto Racing is a family-owned and -operated business venture that sanctions and governs multiple auto racing sports events. It was founded by Bill France Sr. in 1947–48. As of 2009, the CEO for the company is Brian France, grandson of the late Bill France Sr...

, rallying
Rallying
Rallying, also known as rally racing, is a form of auto racing that takes place on public or private roads with modified production or specially built road-legal cars...

, 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 (804.7 km) race may run only 100 miles (160.9 km) before a tire change. Some tire makers invest heavily in race tire development as part of the company's marketing strategy
Marketing strategy
Marketing strategy is a process that can allow an organization to concentrate its limited resources on the greatest opportunities to increase sales and achieve a sustainable competitive advantage.-Developing a marketing strategy:...

Advertising is a form of communication used to persuade an audience to take some action with respect to products, ideas, or services. Most commonly, the desired result is to drive consumer behavior with respect to a commercial offering, although political and ideological advertising is also common...

to attract customers.

Racing tires often are not legal for normal highway use.

### Industrial

The Industrial tire classification is a bit of a catch-all category and includes pneumatic and non-pneumatic tires for specialty industrial and construction equipment such as skid loader
A skid loader or skid steer loader is a small rigid frame, engine-powered machine with lift arms used to attach a wide variety of labor-saving tools or attachments. Though sometimes they are equipped with tracks, skid-steer loaders are typically four-wheel drive vehicles with the left-side drive...

s and fork lift trucks.

### Bicycle

This classification includes all forms of bicycle
Bicycle
A bicycle, also known as a bike, pushbike or cycle, is a human-powered, pedal-driven, single-track vehicle, having two wheels attached to a frame, one behind the other. A person who rides a bicycle is called a cyclist, or bicyclist....

tires, including road racing tires, mountain bike
Mountain bike
A mountain bike or mountain bicycle is a bicycle created for off-road cycling. This activity includes traversing of rocks and washouts, and steep declines,...

tires, snow tires, and tubular tires
Tubular tyres
A tubular tyre, referred to as a tub in Britain, a sew-up in the US, a single in Australia, or just a tubular is a bicycle tyre that is stitched closed around the inner tube to form a torus...

, used also with other human-powered vehicles (see :Category:Human-powered vehicles).

### 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 is distributed better). Aircraft tire tread patterns are designed to facilitate stability in high crosswind
Crosswind
A crosswind is any wind that has a perpendicular component to the line or direction of travel. In aviation, a crosswind is the component of wind that is blowing across the runway making landings and take-offs more difficult than if the wind were blowing straight down the runway...

conditions, to channel water away to prevent hydroplaning, and for braking effect. Aircraft tires are usually inflated with nitrogen
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...

or helium
Helium
Helium is the chemical element with atomic number 2 and an atomic weight of 4.002602, which is represented by the symbol He. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas that heads the noble gas group in the periodic table...

in order to minimize expansion and contraction from extreme changes in ambient temperature and pressure experienced during flight. 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. Aircraft tires generally operate at high pressures, up to 200 psi (13.8 bar; 1,379 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 psi (55.2 bar; 5,515.8 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
Emergency landing
An emergency landing is a landing made by an aircraft in response to a crisis which either interferes with the operation of the aircraft or involves sudden medical emergencies necessitating diversion to the nearest airport.-Types of emergency landings:...

. 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
Autoignition temperature
The autoignition temperature or kindling point of a substance is the lowest temperature at which it will spontaneously ignite in a normal atmosphere without an external source of ignition, such as a flame or spark. This temperature is required to supply the activation energy needed for combustion...

. The use of an inert gas for tire inflation will eliminate the possibility of a tire explosion.

### Motorcycle

There are many different types of motorcycle tires:

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

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
Noise pollution
Noise pollution is excessive, displeasing human, animal or machine-created environmental noise that disrupts the activity or balance of human or animal life...

emanating from moving vehicles. These sound intensities increase with higher vehicle speeds. 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".

### DOT

The United States Department of Transportation
United States Department of Transportation
The United States Department of Transportation is a federal Cabinet department of the United States government concerned with transportation. It was established by an act of Congress on October 15, 1966, and began operation on April 1, 1967...

(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
UTQG
UTQG stands for Uniform Tire Quality Grading.The National Highway Traffic Safety Administration established the Uniform Tire Quality Grading Standards in 49 CFR 575.104.- Treadwear :...

), is a system for comparing the performance of tires, established by the United States National Highway Traffic Safety Administration
The National Highway Traffic Safety Administration is an agency of the Executive Branch of the U.S. government, part of the Department of Transportation...

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" .
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 anbd valves. It is analogous to T&RA and ETRTO.

The Transportation Recall Enhancement, Accountability and Documentation Act
Transportation Recall Enhancement, Accountability and Documentation Act
The Transportation Recall Enhancement, Accountability and Documentation Act is a United States federal law enacted in the fall of 2000. This law intends to increase consumer safety through mandates assigned to the National Highway Traffic Safety Administration...

(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. 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. Fleet operators utilize RFID as part of tire maintenance
Tire maintenance
Tire maintenance for motor vehicles is necessitated by several factors. The chief cause of tire failure is friction from moving contact with road surfaces, causing the tread on the outer perimeter of tires to eventually wear away. When the tire tread becomes too shallow, the tire is worn out and...

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, 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

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 work toward fail-safety such that the failure of the operator to maintain the pressure could be rendered as moot as possible, but there are limits to this pursuit.

### Hydroplaning (or aquaplaning)

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. 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
Bridgestone
The is a multinational rubber conglomerate founded in 1931 by in the city of Kurume, Fukuoka, Japan. The name Bridgestone comes from a calque translation and transposition of ishibashi, meaning "stone bridge" in Japanese....

, Michelin
Michelin
Michelin is a tyre manufacturer based in Clermont-Ferrand in the Auvergne région of France. It is one of the two largest tyre manufacturers in the world along with Bridgestone. In addition to the Michelin brand, it also owns the BFGoodrich, Kleber, Riken, Kormoran and Uniroyal tyre brands...

) 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
The American Broadcasting Company is an American commercial broadcasting television network. Created in 1943 from the former NBC Blue radio network, ABC is owned by The Walt Disney Company and is part of Disney-ABC Television Group. Its first broadcast on television was in 1948...

's 20/20 news magazine found that many major retailers such as Goodyear
Goodyear Tire and Rubber Company
The Goodyear Tire & Rubber Company was founded in 1898 by Frank Seiberling. Goodyear manufactures tires for automobiles, commercial trucks, light trucks, SUVs, race cars, airplanes, farm equipment and heavy earth-mover machinery....

, Wal-Mart
Wal-Mart
Wal-Mart Stores, Inc. , branded as Walmart since 2008 and Wal-Mart before then, is an American public multinational corporation that runs chains of large discount department stores and warehouse stores. The company is the world's 18th largest public corporation, according to the Forbes Global 2000...

, 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.

### Scrap tires and environmental issues

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".

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. 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. Of particular concern is evidence that some of the compounds that leach from tires into water, contain hormone disruptors and cause liver lesions.

## Asymmetric tire

An asymmetric tire is a term used to describe some specific stabilization methods used in car
Čar
Čar is a village in the municipality of Bujanovac, Serbia. According to the 2002 census, the town has a population of 296 people.-References:...

s.

An asymmetric tire may refer to a tire whose tread pattern
The tread of a tire or track refers to the rubber on its circumference that makes contact with the road. As tires are used, the tread is worn off, limiting its effectiveness in providing traction. A worn tire tread can often be retreaded. The word tread is often used incorrectly to refer to the...

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
Automobile
An automobile, autocar, motor car or car is a wheeled motor vehicle used for transporting passengers, which also carries its own engine or motor...

radial tire in which asymmetric structure stabilizing belts are built. Generally the stabilizing belts give a self-aligning torque
Torque
Torque, moment or moment of force , is the tendency of a force to rotate an object about an axis, fulcrum, or pivot. Just as a force is a push or a pull, a torque can be thought of as a twist....

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.

• Camber thrust
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...

• Central Tire Inflation System
Central Tire Inflation System
A Central Tire Inflation System is a system to provide control over the air pressure in each tire of a vehicle as a way to improve performance on different surfaces. For example, lowering the air pressure in a tire creates a larger area of contact between the tire and the ground and makes driving...

• Cornering force
Cornering force
Cornering force or side force is the lateral force produced by a vehicle tire during cornering.Cornering force is generated by tire slip and is proportional to slip angle at low slip angles. The rate at which cornering force builds up is described by relaxation length...

• Direct tire pressure monitoring system
Direct TPMS
Direct TPMS, or direct tire pressure monitoring systems refers to the use of a pressure sensor directly mounted on the wheels or tires of a vehicle. The pressure inside the tire is measured using a pressure transducer with the pressure information being subsequently sent to the vehicle to warn the...

• Dry steering
Dry steering
Dry steering is the act of turning the steering wheel or rotating the steer wheels of a vehicle on the Z axis by some other means, while the vehicle is stationary....

• Groove wander
Groove wander
Groove wander , similar to Tramlining, is a lateral force acting on a vehicle's wheel resulting from the combination of rain grooves and contoured deformations in the road surface upon which the wheel runs....

• Ground pressure
Ground pressure
Ground pressure is the pressure exerted on the ground by the tires or tracks of a motorized vehicle, and is one measure of its potential mobility, especially over soft ground. Ground pressure is measured in pascals which corresponds to the EES unit of pounds per square inch...

• Low-rolling resistance tires
Low-rolling resistance tires
Low-rolling resistance tires minimize wasted energy as a tire rolls, thereby decreasing required rolling effort — and in the case of automotive applications, improving vehicle fuel efficiency. Approximately 5–15% of the fuel consumed by a typical car may be used to overcome rolling resistance...

• Pneumatic trail
Pneumatic trail
Pneumatic trail or trail of the tire is a trail-like effect generated by compliant tires rolling on a hard surface and subject to side loads, as in a turn...

• Relaxation length
Relaxation length
Relaxation length is a dynamic property of pneumatic tires that describes the delay between when a slip angle is introduced and when the cornering force reaches its steady-state value....

• Skid mark
Skid mark
A skid mark is the mark a tire makes when a vehicle wheel stops rolling and slides or spins on the surface of the road. More generally, any solid which moves against another can cause visible marks, and is an important aspect of trace evidence analysis in forensic science and forensic engineering...

• Slip (vehicle dynamics)
Slip (vehicle dynamics)
In vehicle dynamics, slip is the relative motion between a tire and the road surface it is moving on. This slip can be generated either by the tire's rotational speed being greater or less than the free-rolling speed , or by the tire's plane of rotation being at an angle to its direction of...

• Tire-pressure gauge
Tire-pressure gauge
A tire-pressure gauge is a pressure gauge used to measure the pressure of tires on a vehicle. conditions can introduce a 13 to 15 percent variability in pressure due to temperature , and additional changes can result due to altitude...

• Tire-pressure monitoring system
• Tire label
Tire label
The Tire Label is a mark for motor vehicle tires. Manufacturers of tires for cars, light and heavy trucks must specify fuel consumption, wet grip and noise classification of the product by means of a sticker or a label starting in November 2012. This information must also be included in the...

• Tire recycling
Tire recycling
Tire recycling or rubber recycling is the process of recycling vehicles tires that are no longer suitable for use on vehicles due to wear or irreparable damage . These tires are among the largest and most problematic sources of waste, due to the large volume produced and their durability...

• Tramlining
Tramlining
Tramlining is the tendency of a vehicle's wheels to follow the contours in the surface upon which it runs. The term comes from the tendency of a car's wheels to follow the normally recessed rails of street trams, without driver input in the same way that the train does...