>
>
> Two weekends ago I adjusted the endplay of my 64 MGB's front wheel
> bearings. I originally decided to inspect them because at ~65+ mph
> there was a long time small vibration from the right front wheel.
> Upon inspection, the endplay on the right wheel was ~3 times that
> on the left.
>
> I adjusted the endplay so that when firmly grasping the suspended
> tyre at six and twelve o'clock I could feel only a very small amount
> of play when pushing with alternating hands. Listening very carefully,
> I could hear only a very muffled thud when rocking the tyre to and fro.
>
> Life was good. The vibration was gone, but then...
>
> Today, upon hearing peculiar (by not deathly) noises from that corner
> of the car I pulled to side of the road, jacked it up, removed the
> wheel, removed the grease cap, and found a paste of grease and metal.
>
> The bearings had been originally installed only about a year ago.
>
> I assume my endplay adjustment was at fault, although the left side
> wheel bearing which was adjusted in the same way is fine.
>
Most likely. But which time? It's possible the movement/thud you were
feeling was a small amount of slop in the kingpin, and the bearing was
too tight. Or it's possible that the bearing was installed/adjusted
incorrectly the first time, and all the endplay was from the bearing
beginning to fail. Or, a defective bearing.
> Over the past ten years I've installed MGB front wheel bearings a
> few times, and not had any problems. Although, I've always been a bit
> seat of the pants with the endplay.
>
> Are the any Master's tricks to MGB front wheel bearings?
>
> How much endplay is too little? How much endplay is too much?
>
The manuals spell it out pretty well. You measure the endfloat of the
hub with a dial indicator, and adjust the shims to bring it within spec.
I think the spec is .002 to .004, but I'm not near a manual. Doesn't
matter, I don't do it this way.
I set the bearings up by feel. Pulling the hub straight in and out, axial
to the spindle, it should just click, but you shouldn't feel any real
movement.This is done with the road wheel and brake pads removed. Just keep
shuffling shims around until things come out right. A major pain in the rear
on wire wheeled MG's.
Ah, good, the laundry is finally done. Let me just step out for a second
and grab the nomex (heading off to Summit Point tomorrow morning).
You got me on the subject. I'm about to say something that's gonna piss a
lot of people off. Before you reach for the reply key, think the engineering
through. BMC cars need to have the front wheel bearings properly shimmed, and
the retaining nut fully torqued. I've seen a lot of messages on this list
claiming the shims are not needed. Or if you switch from balls to tapers you
can remove the shims, etc. This is not true. The reason for the shims has
nothing to do with the bearing type. It has everything to do with the
spindle and nut design.
The freeplay spec called for is small, and has a very narrow range. This was
done because of the extreme loads the bearings see. But it's a light car, you
say. This is true, but they are also dinky bearings mounted fairly close
together. This narrow base combined with the high torsional loads imposed
on the spindle by spirited cornering lead to extreme loads on the bearings.
The loads are really fearsome. To this day, I do not understand how the
bearings survive as long as they do.
But back to the shims. We have a very narrow tolerance range to hit, .003,
+/- .001. Now, a lot of people leave out the shims (sometimes even the spacer),
and just wind the nut down loose to what feels right. Then they have to turn
it until one of the cotter pin holes lines up. With a little bit of applied
Murphy, this will be up to 1/24 of a turn (12 possible pin hole points per
turn). 1/24 of a turn at 18 threads per inch comes out to a resolution of about
+/- .023. In the real world, people won't accept .023 of endplay. So we end up
with MG's that have from .010 loose to around .035 tight. But even so, a spec
calling out +/- .001, and an adjustment method with a resolution of +/- .023.
Not acceptable in my book.
The first question that comes to mind is why all these cars don't have cronic
bearing failures. I can think of two reasons. The primary one is the .023 is
the maximum things can be off, assuming the best fit has been picked. Most
of the time, the actual error will be less than that. The bearing *could*
end up spot on. The second reason is that the life of a bearing at any
given adjustment is very dependent on the loads. The serious loads come
from hard cornering. Alas, not all MG's are driven as they were meant to be...
>
> ...robert
>
>
Randy
randy@taylor.infi.net
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