If you turn the steering wheel of your car and hear a distinctive “screech” you can be sure that you have a wheel bearing failing. The bearings that support the entire weight of your car rotate millions of time and sooner or later they begin to wear out, the results is the development of excessive play in the bearing. A combination of wear and dirt and water than can slowly permeate the seals will cause the slow erosion of the high tolerance bearing surfaces. Once a wheel bearing begins to wear out there is no repair possible, the entire rear wheel hub which includes the bearing must be replaced. A wheel bearing will not fail in spectacular fashion but once you hear the tell-tale noises you should get your car to a mechanic before it finally gives out.
The rear wheel hub is the component that the wheel bolts to. The hubs spin freely as they carry the wheel bearing; they also carry the disc brake rotor. Wheel hubs can either be driven or they can simply freewheel. In the case of a front wheel drive car it is the rear wheel hub that freewheels. When a wheel bearing fails, the entire hub and bearing assembly is changed, this makes the process considerably less expensive and certainly the repair can be done much quicker. By changing the entire assembly there is no need for special tools or bearing presses.
Anti-lock braking sensors:
Although there are a couple of ways to mount the ABS sensor, they rely on the wheel hubs. The sensor is actually measuring the speed of the wheel. One clever way of doing this is to integrate what is known as a “tone ring” to the hub. The sensor is mounted stationary in close proximity to the tone ring. Other vehicle manufacturers integrate the entire sensor system in the wheel hub which is a simpler solution but it does mean that in the event the sensor should fail, the entire hub must be replaced even though the bearing is in perfect condition.