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
----------
From: Richard Shipman <mbelect@mindspring.com>
To: Mark Endicott <endicott@nashville.com>
Cc: spridgets@autox.team.net
Subject: Re: Front Wheel Bearings...
Date: Sunday, 9 May 1999 6:05
Mark,
Thank you for your informative response.
I would be very interested in how you make out with the NSK bearings.
Also, do you remember the logic used in concluding that the tube adds
significant strength??
My feeling is that it was included to make bearing adjustment
"idiot-proof"
so you can tighten down on the attaching nut as much as you like and not
damage the bearings... anybody have an opinion??
Thanks again for all your helpful information.
Richard
'74 MG Midget
'68 MGBGT
'58 Morris Minor 1000
>Richard,
>
>Several of us have had the problem that you describe when using "after
market"
>(Moss, Mini Mania or VB) wheel bearings. The consensus is that the tube
adds
>significant strength to the axle and should not be removed. I have just
ordered
>new bearings at the suggestion of one of the list members that has
researched
>the problem and has found a good substitute NSK bearings. I will give you
the
>numbers that I have, but you may want to wait until I have installed them
in my
>Midget and get a report. I should receive them next week but I won't get
them in
>until the following week.
>
>NSK 7205BYG (Big One)
>NSK 7303BYG (Small One)
>
>These replace the R & M original bearings R&M 3MJT17 and R&M 34LJT25
>
>Good Luck,
>--
>Mark
>1970 Midget
>Nashville, TN
>
>http://members.home.net/mendicott/midget.html
>http://www.NashvilleTN.org/
>
>
>
>
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