A wheel bearing is an essential component of the car’s hub assembly and is responsible for the smooth rotation of the wheel on its axle.
Most modern cars use sealed bearings consisting of an inner, central and outer race housing 2 sets of bearings (inner and outer). They are lubricated with high temperature grease and sealed to prevent the ingress of moisture and debris.
The sealed bearing unit is pressed into the centre of the hub assembly.
There are generally 2 types of wheel bearing, roller for driven wheels and race or tapered for non-driven wheels.
Due to the high levels of friction and movement the wheel bearing is prone to wear. This is especially likely when water or debris enters the unit. While sealed bearings are maintenance free older style bearings should be regularly greased to prolong life.
Worn bearings should be replaced as soon as possible to prevent additional wear to other components of the vehicle including tyres, hub assembly and suspension.