Wheel bearings are critical to the proper function of a vehicle's hub, tire and wheel assemblies. By allowing friction-free movement and rotation of a vehicle's hub assemblies, wheel bearings promote smooth vehicle tire and wheel motion. Bad wheel bearings, however, negatively affect vehicle tire and wheel operation and produce a variety of symptoms.
The most common symptom of bad wheel bearings is noise coming from the wheel or tire area of a moving vehicle. This is often a grinding, grating noise that gets progressively louder as the vehicle is driven faster. Bad wheel bearings are easily heard, but often not easily diagnosed, at least initially, because they are not a common vehicle part that needs to be regularly serviced or replaced. This means many people are unfamiliar with wheel bearings and the noises they can make when they go bad.
Although excessive wheel noise is the most common symptom of bad wheel bearings, many times a vehicle with bad wheel bearings will not have any noise coming from the wheel or tire area at all. Wheel looseness, or wheel play, is a common symptom of bad wheel bearings. As the wheel bearings degrade and lose their structural integrity inside the wheel hub, they can allow the wheel hub and spindle to become loose, which ultimately gets transmitted to the vehicle wheel and tire, a condition that can be diagnosed by raising the vehicle, grasping the suspected wheel and pulling on it.
Wheel Rotation Restriction
As wheel bearings corrode and/or become pitted and lose their smooth exterior linings, they inhibit the smooth, unobstructed rotation of the wheel hub and spindle assembly, which in turn restricts the spinning motion of the vehicle wheel and tire. This restricted wheel and tire rotation presents itself many times as the vehicle pulling to one side during normal operation, or as the vehicle requiring increased acceleration to attain normal vehicle driving speeds.
Abnormal Tire Wear
If wheel bearings become bad enough, they can have a negative impact on the wear patterns of vehicle tires. Wheel bearings contribute to the overall structural integrity of a vehicle's wheel assemblies, which house and anchor a vehicle's tires. Wheel bearings that become extremely loose or degraded can cause excessive wheel and tire play to develop, and this excessive play can place abnormal stress on a vehicle tire. This stress causes abnormal or premature tire wear to develop.
Front Suspension Looseness
A vehicle that has bad front wheel bearings will often exhibit symptoms of having loose front suspension parts, including symptoms of tie-rod end looseness or control arm bushing looseness. When tie-rod ends and control arm bushings wear excessively, they can produce similar symptoms to that of bad wheel bearings: tire/wheel looseness and/or vehicle front-end sway. Many times bad wheel bearings, especially bad bearings that produce no noise, are diagnosed after eliminating any vehicle front suspension abnormalities as the cause of any suspicious wheel/tire looseness or front-end sway.