Need to Know

Practical Classics (UK) - - CONTENTS -

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

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