Wheel bearings are a component of the vehicle where friction is detrimental to their activity. The bearing must remain free and smooth in its workings in order to ensure the wheel can rotate without impediment.
However, according to bearing manufacturer NTN-SNR, there are a number of issues that can affect the wheel bearing and even the incorrect installation can have detrimental effects. At the recent AutoInform event, the company held a seminar on the causes of wheel bearing failure and what technicians should look out for when it comes to installing them.
There are two types of bearing used, the conventional ball bearing and the roller bearing, used when more load is required to be carried. The latter has a larger surface area which means it can take more weight than ball bearings.
One reason why bearings can be damaged can be found in the state of the UK roads. A sharp shock through the suspension can cause a bearing to impact into the casing, causing an indentation. As the bearing continues to rotate it can wear this away, causing either a flat spot on the bearing itself or a crack in the casing.
Worn seals or incorrect sealing on installation can also cause issues. If this is damaged, water can penetrate causing the surface to become corroded or pitting to occur, in this instance a new bearing is required. NTN-SNR advise that during installation a sealed bearing should never be opened and liquids should not be sprayed on them in case they penetrate the casing.
When it comes to bearing installation, ensuring the correct torque settings are used is vital. A wheel bearing is designed to work with fine tolerances and in order to give it the lifetime that is expected, the correct torque settings need to be used when fitting. Too loose and the bearings will come apart within, too tight and the bearings will be squeezed together causing friction, flat-spotting the plates and wearing quicker. NTN-SNR print manufacturer torque settings on the box of each bearing to ensure technicians don’t make this mistake.
Another common problem the company finds is indentations on the bearing shoulder or even a shoulder breakage. This can be caused by a bearing being fitted off-centre. According to the company there are still some garages that fit bearings using a hammer or rubber mallet to press them into place. This causes a shock in the bearing which can leave an indentation in the casing meaning the movement will no longer be smooth and wear will occur faster. The correct bearing press may cost more than a hammer but will make the work easier and will make for a happier customer than the one who comes back after six months.
Finally, wheel bearings can also be a cause of ABS sensor problems, with the ABS warning light illuminating on the dashboard. The encoder on the bearing casing should be clean and a magnet should never be brought near to them. This can be checked with the NTN-SNR card tester which shows whether the encoder is clean or deteriorated.