Tire is a covering for the outer rim of a wheel. Most tires are made of rubber reinforced with some kind of fabric and are pneumatic (filled with compressed air). They are used on airplanes, automobiles, bicycles, buses, earth-moving and mining machinery, motorcycles, recreational vehicles, tractors, trucks, and many other kinds of vehicles. Some rubber tires, such as those used on many wagons and wheelbarrows, are solid rubber.
The main feature of rubber tires is their ability to absorb the shock and strain created by bumps in the road. Tires help provide a comfortable ride and help protect many kinds of cargoes. The air in a rubber tire supports the weight of a vehicle.
Another important feature of rubber tires is their ability to grip the road. The face of a tire, called the tread, has many deep grooves. These grooves and many smaller slits called sipes make up the tread pattern. The tread provides the traction that enables the tires to grip the road in wet weather. The tire body is composed of the rubber side walls (sides), which cover and protect the rest of the body and are made of high-strength bundles of wire for holding the tire on the wheel rim. The body also contains layers of rubberized cord fabric. Each layer is called a ply.
