Tires , or tyres (in American and British English, respectively), are ring-shaped parts, either pneumatic or solid (including rubber, metals and plastic composites), that fit around wheels to protect them and enhance their function.

Pneumatic tires are used on many types of vehicles, such as bicycles, motorcycles, cars, trucks, earthmovers, and aircraft. Tires enable better vehicle performance by providing traction, braking, steering, and load support. Tires form a flexible cushion between the vehicle and the road, which smooths out shock and makes for a comfortable ride.

History

The earliest tires were bands of iron (later steel), placed on wooden wheels, used on carts and wagons. The tire would be heated in a forge fire, placed over the wheel and quenched, causing the metal to contract and fit tightly on the wheel. A skilled craftsman, known as a wheelwright, carried out this work. The tension of the metal band served the purpose of holding or "tying" the wooden spokes of the wheel together, hence the term "tire". In addition to tying the spokes together, the tire also provided a wear-resistant surface to the perimeter of the wheel. As wheels changed over time, the term "tire" continued to be used for the outer band even when it no longer served the purpose of tying the spokes together.

Tire is an older spelling than tyre , but both were used in the 15th and 16th centuries for a metal tire; tire became the settled spelling in the 17th century. In the UK, tyre was revived in the 19th century for pneumatic tyres, possibly because it was used in some patent documents, though many continued to use tire for the iron variety. The Times newspaper was still using tire as late as 1905.

The first practical pneumatic tire was made by the Scot, John Boyd Dunlop, in 1887 for his son's bicycle, in an effort to prevent the headaches his son had whilst riding on rough roads (Dunlop's patent was later declared invalid because of prior art by fellow Scot Robert William Thomson).

Pneumatic tires are made of a flexible elastomer 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

• 1843 – Charles Goodyear announces vulcanization
• 1846 – Robert William Thomson invented and patented the pneumatic tire
• 1888 – First commercial pneumatic bicycle tire produced by Dunlop
• 1889 – John Boyd Dunlop patented the pneumatic tire in the UK
• 1890 – Dunlop, and William Harvey Du Cros began production of pneumatic tires in Ireland
• 1890 – Bartlett Clincher rim introduced
• 1891 – Dunlop's patent invalidated in favor of Thomson’s patent
• 1892 – Beaded edge tires introduced in the U.S.
• 1894 – E.J. Pennington invents the first balloon tire
• 1895 – Michelin introduced pneumatic automobile tires
• 1898 – Schrader valve stem patented
• 1900 – Cord Tires introduced by Palmer (England) and BFGoodrich (U.S.)
• 1903 – Goodyear Tire Company patented the first tubeless tire, however it was not introduced until 1954
• 1904 – Goodyear and Firestone started producing cord reinforced tires
• 1904 – Mountable rims were introduced that allowed drivers to fix their own flats
• 1906 – First pneumatic aircraft tire
• 1908 – Frank Seiberling invented grooved tires with improved road traction
• 1910 – BFGoodrich Company invented longer life tires by adding carbon black to the rubber
• 1919 – Goodyear and Dunlop announced pneumatic truck tires
• 1938 – Goodyear introduced the rayon cord tire
• 1940 – BFGoodrich introduced the first commercial synthetic rubber tire
• 1946 – Michelin introduced the radial tire
• 1947 – Goodyear introduced first nylon tires
• 1947 – BFGoodrich introduced the tubeless tire
• 1963 – Use of polyester cord introduced by Goodyear
• 1965 – Armstrong Rubber introduced the bias belted fiberglass tire
• 1965 – BFGoodrich offered the first radial available in North America
• 1967 – Poly/glass tires introduced by Firestone and Goodyear
• 1968 – United States Department of Transportation (DOT) numbers required on new tires in USA
• 1974 – Pirelli introduced the wide radial tire

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

Terms

Tread

The tread is the part of the tire which comes in contact with 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. Tread patterns feature non-symmetrical (or non-uniform) lug sizes circumferentially in order to minimize noise.

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.

Treadwear

The treadwear grade describes how long the tire manufacturer expects 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. In general, manufacturers tend to overstate the treadwear of their tires in an effort to create the impression that their tires last a long time. The ability of manufacturers to report their own numbers makes comparison of treadwear ratings between companies useless. Ratings may still be useful within a manufacturer's own line of tires.

Tread lug

Tread lugs provide the contact surface necessary to provide traction. As the tread lug enters the road contact area, or footprint, it is compressed. As it rotates through the footprint it is deformed circumferentially. As it exits the footprint, it recovers to its original shape. During the deformation and recovery cycle the tire exerts variable forces into the vehicle. These forces are described as Force Variation.

Tread void

Tread voids provide space for the lug to flex and deform as it enters and exits the footprint. Voids also provide channels for rainwater, mud, and snow to be channeled away from the footprint. The void ratio is the void area of the tire divided by the entire tread area. Low void areas have high contact area and therefore higher traction on clean, dry pavement.

Rain groove

The rain groove is a design element of the tread pattern specifically arranged to channel water away from the footprint. Rain grooves are circumferential in most truck tires. Many high performance passenger tires feature rain grooves that are angled from the center toward the sides of the tire. 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 in the lug and reduces heat build up. Sipes also provide greater traction in icy conditions.

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.

Contact patch

The contact patch, or footprint, of the tire, is merely the area of the tread which is in contact with the road surface. This is the area which transmits forces between the tire and the road via friction. The length-to-width ratio of the contact patch will affect steering and cornering behavior.

Bead

The bead is that part of the tire which contacts the rim on the wheel. The bead is reinforced with steel wire, and compounded from 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 are a factor in the handling characteristics of an automobile because the rim supports the tire's profile.

Sidewall

The si

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