What Are Your Car’s Wheel Bearings?
As well as supporting the weight of vehicle and occupants, wheel bearings also have to absorb the heat and friction which are generated during typical driving conditions.
Most wheel bearings consist of a set of steel ball bearings, which move around inside a metal frame called a race. This is a bit like a railway track in that it consists of two parallel rings, which should ideally be perfectly circular. The outer rims should be able to hold the bearings tightly, yet still allow the inner bearings to move around freely within this frame.
Wheel Bearing Replacement - Once Simple, Now More Complicated.
They may have a hard job to do, but the advent of more complicated, computer-controlled braking systems for most vehicles has also made the mechanisms in which wheel bearings are mounted far more complex.
Replacing wheel bearings used to be a straightforward task - the mechanic would remove the old part, re-fit a new one, then generously fill the area around it with grease.
But now, a typical wheel hub assembly will also incorporate the ABS sensor, which keeps track of the vehicle’s speed. So a faulty ABS sensor may also mean that the whole wheel hub assembly has to be replaced.
Also, most wheel bearing sets are now sealed, meaning that whenever they start to make a noise - the first and most common sign of a wheel bearing failure - the whole wheel hub has to be replaced, and not just the wheel bearing itself.
How Will You Know When Your Car Needs Its Wheel Bearings Replaced?
Why do wheel bearings start to make a noise? While the hardened steel from which most wheel bearings are made can withstand a lot of regular wear and tear, and even abuse, the parts’ two worst enemies are heat and water. Lubrication is vital in keeping the levels of heat under control, so if this is neglected, it can lead to terminal wheel bearing damage. Equally, if water penetrates inside a bearing which is supposedly sealed, or the bearing has been damaged through wear or impact caused by a bad road surface, this could mean replacement is needed.
While the bearings are meant to be protected from water, debris and other contaminants by seals around the wheel rim, these seals themselves can get broken or damaged, and lead to the bearing making a noise which is the first sign that it is about to fail.
Added to this is the difficulty in detecting which wheel is the source of the noise - and it’s a problem which can have even an experienced mechanic scratching their head.
Finding the source of a problem with wheel bearings may involve putting the car up on a jack or lift, and manually rotating the wheels. The mechanic may then hear a different sound which will lead them to the source of the problem, or he/she might notice some play (i.e side-to-side movement) in the wheel as they turn it.