Servicing Wheel Hubs and Bearings

auto mechanicsWheel hub bearings may not be visible when you’re scanning the outer body of a vehicle, but they play an important role in its safety and handling characteristics. Comprised of precision-manufactured bearings, seals and sensors in one pre-assembled unit, a wheel hub bearing unit is critical to a car’s performance.

Although wheel bearings on late model vehicles are sealed and require no maintenance or adjustments, they won’t last forever. Quite often, auto mechanics overlook hub bearing when working on brakes, suspension, or changing tires.  But failing to ensure their integrity can have disastrous results!

When the wheel hub bearing unit degrades, the results can range from an annoying wheel vibration and noise – to a malfunction in the anti-lock brake system or a wheel that actually breaks off while the vehicle is in motion. Here are a few things to keep in mind when servicing wheel hubs and bearings:

First Signs of Trouble

Effective auto mechanic training teaches students to watch for key signs that hub wheel bearings need to be replaced. Usually located in the wheel’s hub, rotor, or brake drum, bearings help the wheel rotate smoothly when the vehicle moves – so if the car owner reports hearing a whirring or humming noise while driving or the ABS light comes on, chances are the hub bearings need some attention. Other symptoms include a grinding noise while steering, steering wander, or possibly a pull to one side when braking.

auto mechanic training

Guide to Inspection

To check a wheel bearing, the auto technician should grasp the wheel at top and bottom and attempt to rock it. If there’s any movement there, it means the bearings are loose and need to be replaced. Another option is to rotate the wheel by hand – any roughness or noise will tell you that the bearings are worn or damaged.  If the vehicle has a lot of miles on it, and one wheel bearing has given out, be sure to check all of the others as well. Chances are, they are nearing the end of their lifecycle.

Wheel Hub Repairs

There is no way to disassemble and repair a sealed hub assembly. If something has gone wrong with the unit – like a failed internal ABS sensor or corroded ABS tone ring on the hub – the entire thing must be replaced.  Mechanics will need to remove the wheel, hub nut and brakes to replace the unit. On the other hand, if you’re working on an older vehicle, adjustable wheel bearings can be adjusted, cleaned and repacked with grease, and replaced if the bearings are bad. A leaky grease seal can also be corrected without having to replace the bearings, too.

Here’s a great little video for diagnosing noisy wheel hubs and bearings:

What symptom have you found to be most commonly associated with damaged wheel hub bearings?

Categories: ATC News, Montreal
Tags: auto mechanic training, auto mechanics, auto technician

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