ALT-1 What can Happen when Wheel Bearings Fail
Automotive wheel bearings carry most of the vehicles weight and provide a low friction surface between the rotating wheel and non rotating spindle or between the rotating axle and non rotating axle housing. With proper lubrication they can last well over 100,000 miles depending on use and road conditions. The bearing assemblies consist of a number of hardened steel rollers and inner and outer races made of softer metal that the rollers roll on. Most vehicles have two roller bearing assemblies on each wheel. Some wheel bearing assemblies have two sets of bearings encased in a single multi-race housing. The lubrication for the bearings is provided by heavy weight high temperature grease.
Failuresoccur when the rollers or races become damaged or worn. This can come from normal wear, lack of lubrication, contamination of lubricants, or physical damage. Under normal wear the races wear much faster than the rollers and allow the wheel to wobble. This can be felt as vibrations at high speeds, shuddering when breaking and a tendency for a vehicle to “follow cracks” in a road. Worn bearings can cause excessive tire wear. There are many other suspension failures that can cause these same problems.
Lack of lubrication will cause critical failure of bearings in a very short period of time and can damage other parts. When the lubricant is insufficient the bearing temperature will rapidly increase while vehicle is moving. The increased temperature will burn off any remaining lubricant and the bearing overheats. The first signs may be squealing from the wheels followed by grinding noises. At this point the bearing has failed and any further use will damage wheel hubs, spindles or axles.
Contamination of lubricant can come from long storage periods of disuse. The lubricant becomes hard and moisture can intrude and corrode and pit the rollers. Contamination can also occur when hot bearings are exposed to deep water and rapidly cooled, a common event when launching boats after long road trips. As the bearings cool they can draw muddy water and sediments into the bearing housing. The sediments are abrasive and can cause premature wear of races and rollers.
Physical damage can occur from accidents or hitting pot holes at high speed. Out of balance wheels can also damage bearings. These forms of damage can put flat spots in races or crack rollers causing vibration and/or premature bearing failure. Generally other suspension parts are more susceptible to damage from these events, but when ball joints or support members have been damaged it maybe a good idea to replace or at least inspect wheel bearings.
