Rain Tyre
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A rain tyre or wet tyre (spelt tire in
American English American English, sometimes called United States English or U.S. English, is the set of variety (linguistics), varieties of the English language native to the United States. English is the Languages of the United States, most widely spoken lang ...
, commonly shortened to wet) is a special tyre used in
motorsport Motorsport or motor sport are sporting events, competitions and related activities that primarily involve the use of Car, automobiles, motorcycles, motorboats and Aircraft, powered aircraft. For each of these vehicle types, the more specific term ...
in wet weather as opposed to a slick tyre used in dry conditions. It is very similar in many ways to the tyres found on normal road cars. Rain tyres are not used in
NASCAR The National Association for Stock Car Auto Racing, LLC (NASCAR) is an American auto racing sanctioning and operating company that is best known for stock car racing. It is considered to be one of the top ranked motorsports organizations in ...
, ARCA and
INDYCAR IndyCar, LLC (stylized as INDYCAR), is an auto racing sanctioning body for American open-wheel car racing headquartered in Indianapolis, Indiana. The organization sanctions two racing series: the premier IndyCar Series with the Indianapolis ...
sanctioned races held on oval tracks as these races are invariably halted when the track is wet due to safety concerns regarding the large amounts of spray involved reducing visibility, as well as a lack of traction in banked corners at high speeds.


Structure

Rain tyres have a specially designed structure making them better adapted for their application than any other tyres. However, not all rain tyres obey the same design principles. Certain factors need to be taken into account when designing a good rain tyre, such as the: *Speed of the car *Weight of the car *Power of the car *Lifespan of the tyre


Grooves

Rain tyres are cut or moulded with patterned grooves or tread in them. This allows the tyre to quickly displace the water between the ground and the rubber on the tyre. If this water is not displaced, the car will experience an effect known as hydroplaning as the rubber will not be in contact with the ground. These grooves do not help the car grip contrary to popular belief, however if these grooves are too shallow, the grip will be impaired in wet conditions as the rubber will not be able to make good contact with the ground. The patterns are designed to displace water as quickly as possible to the edges of the tyre or into specially cut channels in the centre of the tyre. Not all groove patterns are the same. Optimal patterns depend on the car and the conditions. The grooves are also designed to generate heat when lateral forces are applied to the tyre.


Rubber

Rain tyres are also made from softer
rubber Rubber, also called India rubber, latex, Amazonian rubber, ''caucho'', or ''caoutchouc'', as initially produced, consists of polymers of the organic compound isoprene, with minor impurities of other organic compounds. Types of polyisoprene ...
compounds to help the car grip in the slippery conditions and to build up heat in the tyre. These tyres are so soft that running them on a dry track would cause them to deteriorate within minutes. Softer rubber means that the rubber contains more oils and other chemicals which cause a racing tyre to become sticky when it is hot. The softer a tyre, the stickier it becomes, and conversely with hard tyres. When rain has stopped falling, and a track is in the process of drying, it is not unusual to see drivers intentionally driving through wet puddles and damp portions of the course, in order to cool the rubber and stave off tyre deterioration. As soon as possible, drivers will revert to slick tyres to maintain competitive speeds.


Shape

Currently, F1 rain tyres have a larger diameter than dry tyres, with the wets having a diameter of 10mm more than the slicks. This increases the ride height of the car and makes it less vulnerable to aquaplaning. Sometimes rain tyres are designed to have a smaller diameter than their dry counterparts. This means that the wheel spins faster and more water is thrown off the tyre by overcoming
centripetal force Centripetal force (from Latin ''centrum'', "center" and ''petere'', "to seek") is the force that makes a body follow a curved trajectory, path. The direction of the centripetal force is always orthogonality, orthogonal to the motion of the bod ...
. Some rain tyres are also narrower than the dry counterparts. This smaller "footprint" reduces the chances of hydroplaning.


Intermediate tyres

Some racing series such as
Formula One Formula One (F1) is the highest class of worldwide racing for open-wheel single-seater formula Auto racing, racing cars sanctioned by the Fédération Internationale de l'Automobile (FIA). The FIA Formula One World Championship has been one ...
allow an intermediate (inter) tyre. This tyre is designed to be used in conditions too wet for slick tyres and too dry for wet tyres. They are made with rubber compounds slightly softer than slick tyres and are cut with grooves like the rain tyre but shallower to prevent excessive heat build up. Former Formula One tyre supplier
Bridgestone is a Japanese multinational manufacturing company founded in 1931 by Shojiro Ishibashi (18891976) in the city of Kurume, Fukuoka Prefecture, Fukuoka, Japan. The name Bridgestone comes from a calque translation and transposition of (), meaning ...
referred to the "intermediate" tyre as the "wet" tyre, and to what are known as "full wets" as "monsoon tyres".


Invention

The original invention of the rain tyre is attributed to
Uniroyal Uniroyal, formerly known as the United States Rubber Company, is an American manufacturer of tires and other synthetic rubber-related products, as well as variety of items for military use, such as ammunition, explosives, chemical weapons and op ...
, in 1969. They were the first to understand the water-deflecting properties of directional V-shaped tread and the first to use biomimicry with the development of “Shark Skin Technology”, which helps to prevent
aquaplaning Aquaplaning or hydroplaning by the tires of a road vehicle, aircraft or other wheeled vehicle occurs when a layer of water builds between the wheels of the vehicle and the road surface, leading to a loss of traction that prevents the vehicle ...
.


References

{{Tires Tires Vehicle modifications