Tire Basics

Simply put, a tire is a flexible container of compressed air. This air container support the vehicle's load; propels a vehicle forward, backward and side-to-side; stops the vehicle; and cushions the load from road imperfections.

Today's tires have between 19 and 25 different components. Tires are built from the inside out rather than the outside in. The heart of every tire is an inner liner. Its job is to give the tire shape and hold in air. Fabric belts are wrapped around the inner liner. The bead is fastened to the bottom of the fabric belts and holds the tire to the wheel.

Tire Image Gallery 


Photo courtesy Bridgestone Firestone
Cutaway of a Bridgestone Potenza. Here you can see the main components: the inner liner, the fabric and steel belts, the bead, the tread, and the sidewall.
See more pictures of  tires.
On top of the fabric belts are steel belts. These belts have two jobs: They give the tire stability and make the tread pattern as flat as possible. (A flatter tread means more contact with the road.) The tire tread is on top of the belts. There are different tread patterns for different types of tires. The sidewell on the side of the tire gives it stiffness and ride characteristics. A taller, softer sidewall will absorb more bumps, while a shorter, stiffer sidewall will provide better cornering ability and sharper steering response.





On the sidewall of every passenger-car and light-truck tire is an alphanumeric code that describes the dimensions of the tire. For most tires, this code will start with a "P" (above, left). Some may start with an "LT" to signify light truck. Some tires may have a "Max. Load" indication (above, right). When selecting new tires, it is important to make sure a tire's load rating is at least a high as the tire you are replacing.

Tire Rotation
Rotating a vehicle's tires is essential to prevent uneven tire wear. If left unchecked, un-rotated tires will cause increased road noise, lower fuel economy, and decreased wet-weather traction. Badly neglected tires will also have to be replaced sooner.

It is generally accepted that on front-drive vehicles, where all tires are the same size, you rotate the front tires to the rear in a straight line and cross the back tires to the front. In a rear-drive vehicle, you rotate the backs in a straight line to the front and cross the front tires to the back.

On all- or four-wheel-drive vehicles, the rotation pattern most often suggested is a simple "X." The left front and right rear swap places, and the right front and left rear swap places.

Many sports cars and some luxury and sport-utility vehicles have unidirectional tires. Unidirectional tires have tread patterns that are designed to perform in the direction denoted on the tire sidewall only. They should always be rotated front to rear (assuming they are the same size). This ensures that the direction of revolution does not change.

If you are rotating a full-size spare into the mix, it is common practice to put that tire in the right rear. Consumers should consult their owner's manual for the correct tire-rotation procedure for their vehicle.