Though wheel bearings are small, they play an important roll in a car's suspension. Located between the hub and the axle or spindle, wheel bearings ensure the wheel stays in its proper orientation and also ensures the wheel rolls smoothly while a car is being driven. A failed rear wheel bearing can cause a potentially dangerous situation.
Wheel Bearing Description
Wheel bearings consist of a circular row of bearings inside a round housing that is pressed around the bearings. The bearings are what allow the wheel to rotate smoothly. The bearings are covered in a generous quantity of wheel bearing grease and are protected by some type of cap or seal inside the hub housing.
What Causes Bearing Failure?
Wheel bearing failure can be caused by a number of symptoms. Prevent dirt, oil and debris from entering the bearing housing, which can cause the ball bearings to become scored and damaged and eventually fail. Another factor that can cause bearing failure is the wrong wheel or an incorrect alignment. Do not install wheels on your car with too strong of an offset, which can cause the wheel to stick out too far from the suspension and place improper loads on the bearing and cause eventual failure. Improper alignment can cause similar problems. Another factor that may cause a bearing to fail is simply use. Most bearings are designed to last from 80,000 to 100,000 miles. At this point, have your bearings replaced as preventive maintenance.
Symptoms of a Bad Wheel Bearing
A bad wheel bearing will display several symptoms that can be detected. While driving, listen for a variety of noise from a bad bearing, including rubbing, a gently "shushing" sound, or even squeaking. This will get worse during cornering, when load is increased on the bearing. And though it is not as noticeable as a bad front wheel bearing, a bad rear wheel bearing may cause a vague feeling from the suspension, particularly during cornering. A bad bearing may also make it difficult to properly align a suspension. On modern cars with ABS (anti-lock brakes) a bad bearing may cause the car to display an "ABS" light and disable the ABS. If your car is displaying an "ABS" warning light, have your mechanic look at your wheel bearings.
Checking a Wheel Bearing
A failed wheel bearing can cause loss of control of a vehicle and can even cause the wheel to become disconnected from the car. To check a wheel bearing, jack up the vehicle so the wheel is suspended in the air. With your hands placed firmly on either side of the tire, rock the wheel and tire back and forth. There should be no movement. If there is, the bearing is worn and needs to be replaced. Also, spin the wheel to make sure it spins smoothly and does not make any rubbing or scraping sounds as it spins.