Hi Peter,
Thank-you for the most comprehensive and enlightening explaination of the
purpose of the bearing spacer.
Now I finally understand the "rest of the story"!
I'll be much happier "living" with a little wheel rock than "dying" for that
perfect adjustment!
Richard
'74 MG Midget
'68 MGBGT
'58 Morris Minor 1000
'85.5 Porsche 944
At 11:20 PM 5/9/99 +1000, you wrote:
>Not opinion but fact as explained to me by a GM engineer. Firstly, Sprite
>wheel bearings are non-adjustable and there will always be some play.
>Secondly, the spacer DOES add strength to the whole assembly by
>pre-stressing the stub axle when the hub nut is tightened to the correct
>torque (25 -65 ft/lb to accomodate going to the next split pin hole).
>Thirdly, don't forget Sprites were built from the lowest spec parts BMC had
>available and are operating way above their original design parameters. We
>had a spate of stub axles failures in the 70's which concentrated our minds
>in this area, I can still see my friend's Bugeye cartwheeling down the
>track in front of me after a stress failure.
>
>If suspension loads are applied to the bare spindle it will eventually
>break, just as a nail stuck into a piece of wood will break if you bend it
>back and forwards. With the correct torque (as if you've hammered a nail
>home down a length of tube) the spindle (nail) is in tension and the spacer
>(tube) is in compression. This preloaded assembly will now resist
>suspension loadings because for any load to bend the spindle it must
>stretch the spindle or collapse the spacer which is locked between the
>inner races of the bearings. The materials are stronger in compression and
>tension than bending so the force required to bend an unsupported spindle
>will now be too weak to flex a pre-loaded assembly unless the nut is too
>loose. Other cars with tapered bearings have spindles designed to resist
>suspension loads without pre- stressing but this isn't the case with a
>Sprite. Another important consideration is that locking the bearing inners
>will stop them from spinning on the spindle and welding themselves on.
>MGBs have a similar system which is adjustable on initial assembly by
>inserting shims between the outer bearing and the spacer. If you must to
>use adjustable bearings on a Sprite use this method by grinding down the
>spacer and adding shims until adequate clearance is achieved. It's
>imperative that the spacer be locked between the inner bearing races.
>
>HOWEVER nothing lasts forever and every Sprite I've had has had cracked
>stub axles, probably due to age, material specs and incorrect maintainence.
> For peace of mind I crack test the stubs, rear axle ends and Bugeye wheels
>each Spring. For our competition car I got a pair of remanufactured stub
>axles from (I can't remember their name, from memory they were down Rocky
>River Rd in Ohio?) which use a high tensile stub TIG welded into the
>original sub axle casting.
>
>Peter Westcott
>
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