Need to Know
All you need to know about bearings.
Abearing or bush is used to help things along wherever any two parts rotate relative to each other. It provides a point of contact and support between the rotating shaft and its housing.
A bearing or bush is made of materials that are more free-running than those of the shaft and the housing themselves, reducing friction and noise. Importantly, too, it’s a consumable part. When it wears out, the housing and shaft are still absolutely fine and the worn-out item can be discarded and replaced at modest cost. Many forms of bearings and bushes can be found in a classic car – from the crankshaft, to the hubs to the alternator or dynamo.
In this feature, we’ll show you what they consist of, why they’re used and how to look after them. You’ll inevitably need to replace bearings from time-to-time and we’ll cover the basics of doing this, too. It’s usually a simple DIY job, though in some instances a press or puller might be needed.
A workshop manual will give full details of how to replace specific bearings on your classic car. It’s a good idea to consult it to make sure you don’t meet any nasty surprises along the way. Releasing a circlip that holds a bearing on a shaft, for example, might cause the shaft to fall into the casing.
The manual may specify that you install the bearings with bearing fitting compound. This is an adhesive that helps to fix the bearing in position. It can also be used to hold a bearing that unexpectedly turns in its housing or on its shaft after fitting – although heat expansion will often take care of this in engines and gearboxes. If either the housing or the shaft is badly worn, though, it will need to be properly repaired or replaced. Use a low-strength bearing fitting compound – high-strength types are absolutely permanent and it’s likely that you’ll cause damage to the housing, shaft and bearing during any subsequent attempt at dismantling.
How to fit Don’t strain a bearing while installing it. Push onto a shaft by the inner track only and into a housing by the outer track. Bearing upgrade Non-sealed ball bearings in older wheel hubs, dynamos and similar can usually be replaced with modern sealed-for-life items. Get good ‘uns Buy the best bearings you can reasonably afford.
‘Spinning a bearing by hand will tell you a lot about its condition. It should be smooth and silent, with a little ‘stiction’ from the grease inside.’ Ed says