Tire

A tire (U.S. spelling) or tyre (UK spelling) is a roughly toroidal piece of material placed on the circumference of a wheel, either for the purpose of cushioning or to protect the wheel from wear and tear.

Pneumatic tires

Air-filled tires are known as pneumatic tires, and these are the type in almost universal use today. Pneumatic tires are made of a flexible elastomer material such as rubber with reinforcing threads/wires inside the elastomer material. The air compresses as the wheel goes over a bump and acts as a shock absorber. Tires are inflated through a Schrader valve. Attempts have been made to make various types of solid tire but none has so far met with much success. The "steering feel" of such tires is different from that of pneumatic tires, as their solidity does not allow the amount of torsion that exists in the carcass of a pneumatic tire under steering forces, and the resultant sensory feedback through the steering apparatus.

Related Topics:
Elastomer - Rubber - Shock absorber - Schrader valve

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A common motor vehicle tire is mounted around a steel rim at service stations or repair shops for vehicles using a special tire mounting apparatus while the wheel is off the vehicle. After mounting, the tire is inflated (pressurized) with air through the valve stem to manufacturer's specified pressure, which is more than atmospheric pressure. The rim with the tire mounted onto it comprises the removable wheel, which is then attached to the vehicle through a number of holes in the rim using lug nuts. Because tires are often not made with perfectly even mass all around the tire, a special tire-balancing apparatus at a repair shop spins the wheel with the tire to determine where small weights should be attached to the outer edge of the rim to balance out the wheel. Such tire balancing with these kind of weights avoids vibration when the vehicle is driven at higher speeds. The same device used to mount a tire onto a rim is also used to remove a tire from the rim, again when the wheel is off the vehicle. On the wheels of many vehicles, hubcaps are often snapped in place over the part of the rim facing outside and the tightened lug nuts for decoration and, to some extent, for protection from the elements to reduce rusting of the rim and lug nuts. Some rims are already decoratively made and plated with chrome, so hubcaps are not used over them. The hubcap must be removed to take off the tire, and after the tire is replaced, the hubcap is put back on.

Related Topics:
Steel - Rim - Service station - Vehicle - Valve stem - Pressure - Atmospheric pressure - Wheel - Mass - Weights - Balance - Vibration - Hubcap

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The outer perimeter of the tire, often called the crown, has various designs of jagged shaped grooves in it. These grooves are especially useful during weather with rain (or snow). The water from the rain would be compressed into the grooves by the vehicle's weight, providing better traction in the tire to road contact. Without such grooves, a layer or film of water would form between the wet roads and the tire surface, which would substantially reduce the traction making the tire contact with the road very slippery. Traction is especially important for good braking. The depth of these grooves essentially constitutes the tread depth at any time during the lifetime of the car. When the tread on the outer perimeter of the tire inevitably wears away from use, reducing the tread depth, the tire should be replaced. The sidewalls are the sections of the tire which are between the crown and the inner circular edges of the tire contacting the rim. To avoid tearing at these inner edges, particularly when the tire is being mounted, there are a number of concentric steel wires buried inside the rubber at both inner edges of the tire.

Related Topics:
Perimeter - Rain - Snow - Braking - Depth

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Some air-filled tires, especially those used with spoked wheels such as on bicycles, or on vehicles travelling on rough roads, have an inner tube; this was also formerly the case of automobile tires. This is a fully sealed rubber tube with a valve to control flow of air in and out. Others, including modern radial tires, use a seal between the metal wheel and the tire to maintain the internal air pressure (tubeless tire). This method, however, tends to fail desperately if the vehicle is used on rough roads (for example Kenyan roads) as a small bend on the rim (metal wheel) will result in deflation. The inner tubes are usually made of halobutyl rubber, because of its suitable mechanical properties and excellent impermeability for air.

Related Topics:
Spoked wheels - Bicycles - Kenya - Halobutyl rubber

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Pneumatic tires generally have reinforcing threads in them; based on the orientation of the threads, they are classified as bias-ply/cross ply or radial. Tires with radial yarns (known as radial tires) are standard for almost all modern automobiles.

Related Topics:
Bias-ply - Cross ply - Radial - Automobiles

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