Wheel Bearings

A wheel bearing is a set of steel balls held together by a metal ring called a race. They help wheels spin fast with as little friction as possible. They are used on all kinds of vehicles, from bicycles to aircraft and cars. On a car, a wheel bearing rides on a metal axle shaft and fits tightly inside the hub, which is a hollow chunk of metal at the center of the wheel. The hub holds the lug bolts that you use to bolt the tire onto the wheel. The wheel bearing is pressed into the hub from the back.