Tuesday, January 29, 2008

Automobile Tire

Tire are rubber and fabric devices that, when attached to the wheels of a vehicle, provide the contact between the vehicle and the road surface, tires also support the weight of the vehicle. They may be solid or pneumatic (air-filled) in structure, with the latter by far the most prevalent today. Compressed air within the tire carries 90 percent of the load, with the tire's complex structure of rubber and fabric carrying the remaining 10 percent.

ConstructionThe tread of the tire grips the road surface, and the supporting sidewalls run from tread to wheel trim. Tread patterns are especially important when the road is wet. Continuous channels from the center to the edge of the tread direct the water outward. Otherwise, water would form a wedge and cause the tire to lift off the road. This so-called aquaplaning phenomenon is one reason that smooth tire are dangerous in wet conditions. Snow tires and off-highway tires have deeper treads or separate cleats.

A tire's sidewalls flex up and down, helping cushion the vehicle from road irregularly in order to transfer loads of steering, braking, and acceleration. At their innermost edges, sidewalls meet the tire's breads (hoops of steel wire covered with hard rubber). Each bead reinforces the interface between the tire and wheel-rim and flexes the tire's inner diameter.

Reinforcing cords, which give the tire its strength, are arranged beneath the tire's surface. The three classes of modern tires can be distinguished by the direction of the cords. A bias-ply-tire, the earliest, has two or more plies of cord running across the tire at an angle, or bias, from the placed between the plies. A radial tire has reinforcing cords running hoop-fashion from bead to bead. Like a bias-belted tire, a radial has reinforcing belts under its tread, but radial belt cords are angled closer to the tire's centerline. The lack of bias sidewall reinforcement makes a radial's sidewalls more flexible. This gives the tread a better grip and longer life.

Tire construction begins with the sidewall. The different necessitated by the different requirements of each part of the tire are brought together to formed from wound and rubber-coated steel wires. Steel or synthetic-fiber fabric is rubber-coated and cut either at an angle or straight across, depending on tire type. All these materials are assembled for hand lay-up on a rotating, collapsible drum. Next, the beads and tread-sidewalls strip are added. Finally, a heated the tread pattern and vulcanized the rubber.

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