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MG MGB Technical - Trouble with front wheel bearings

Hello all,

I've got a '71 mgb roadster with standard wheels for which I just purchased MGB front wheel bearings from Moss and I am having a problem with them.

All of my reference books say that the outer bearing race needs to be pressed into place in the hub but it my case, the outer race is a very loose fit - enough so that it drops in place, and I can wiggle it around in place (the inner race was a tight fit and needed pressing in).

As a result, with the hub fully assembled with no shims installed, and the hub nut tightened all the way, the hub still has a serious wiggle (top to bottom). It's clear that this movement is coming from the poor fit of the outer race in the hub.

The outer bearing part is Powerdrive LM11949/10. Am I missing something? Is this the incorrect part for my car?

Thank you,

--Paul Elseth
Paul Elseth

I don't think you are missing anything Paul. Presumably you had to drive the original bearing out from the rear in which case your supplier has given you the wrong parts. Take the original to him and get him to supply you with an exact equivalent.

There is no doubt that your car must NOT be run in its current condition.
Iain MacKintosh

Paul
Those outer bearing part numbers are correct (inner race LM11949 outer race LM11910)and the outer races are usually a good tight (hammer and drift) fit. Do you have the old bearings to compare with or did you get the hub bare? If it's a used hub and the old outer bearing seized it may have spun its outer race in the hub and caused the excess clearance (the inner is locked tight on the stub axle).
Rich
R Maile

Thanks for the info, guys.

I've had the car for about 20 yrs now, and I've replaced the wheel bearings a couple of times over the years.

I recently replaced the wheel bearings on both sides with Moss bearings with these same part numbers. I first noticed a certain "looseness" to the hubs at that time, which I thought might be attributable to the new bearing spacers I had also put in (they seemed to be the only changed variable in the equation).

When I got around to checking them again, the wobble was more pronounced, so I decided to start from scratch and work it all out again. Unfortunately at this point I no longer have the older set of bearings, only the set I just took out. I no longer have any confidence that the outer race on this set was a correct fit.

What is the best course of action at this point? Try bearings from another supplier? Do I need to replace the hub? It is possible to fit a bearing with a slightly larger outside diameter on the race?

--Paul
Paul Elseth

If you've a mic or decent caliper you could check the size; the inner is .75"/19.05mm and the outer 1.781"/45.237mm. Failing that pop it down to a local bearing stockist who would be able to mic it and would probably have another in stock to compare it with as it is fairly common. Those numbers should be engraved on each race and if they are I can't really see them being wrong. That would mean your hub is probably best replaced. I find it easiest to shim up with the bearings "dry", just the packing lube on them, and the oil seal not fitted. That way it's easy to take off and on a couple of times and feel for the number of shims to give 2 thou clearance. (My last efforts came out needing 45 thou shims for one side and 48 thou the other but I don't know how common that would be.)
regards, Rich.
R Maile

I really can't see the hub being the problem especially if it was previuusly OK but as Rich says take it with you to a bearing stockist. It seems strange but I'm convinced that the outer race was the problem.

Shim it any way you like the way described is fine. As a starting point the shim pack I always understood to be nearest was 1mm + 5 thou. Now that is a very strange combination of metric and imperial but it works and is almost identical to Rich's sizes.
Iain MacKintosh

Different spacers shouldn't make any difference, that is one of the parts the shims take account of. The inner races of each bearing, spacer and shims should all be clamped up tight to at least 70 lb ft, which should leave slight end-float on the outer races and hence the hub of .002" to .004". If the shimming is incorrect the hub could well be very sloppy (or the bearings stiff if the error is the other way). Without any spacers and tightened up it should be stiff. But nothing will be right until the outer races of the bearings are an interference fit in the hub.
Paul Hunt

Paul,

We recently had the same problem with an MGB front wheel bearing kit. The outer part of the outer bearing was not the correct diameter. These things happen! Phone your supplier for a replacement. These things are so cheap that they are unlikely to need the parts you have returned to them.

If the original had to be drifted out and the new part is smaller then it is the wrong part!

Doug

You are allowed from 40 to 70 lb feet to align the castelated nut with the split pins , and the torque will affect the clearance set with shims. I get the 4 thou set, and also find without the grease is a big help , then torque to 40 lb feet. Reset the torque wrench to 70 and slowly crank the nut round until the split pin will drop into one of the holes.This always happens before the wrench clicks again. Then a final check with the dial gauge before you pin the nut .Sounds a lot of fuss , but is really quick and easy .
S Best

Gentlemen,

Thank you all for your highly relevant and useful information.

Armed with what you all had written, I re-examined the hub and it was quite obvious then that the hub was quite worn (as was the old bearing race).

I took the hub to a machine shop and had them bore it out, insert a sleeve then bore that out to the correct diameters. The race now fits perfectly, and the front suspension is back to where it should be.

One other small question -

I set up the end float (trial-and-error method) just right before packing the bearings as many have suggested. With the grease added, there was a big more drag on the wheel when tightened up. I assume this is due to the slightly tighter fit from the grease, or maybe just the viscosity - but should I have fiddled with the shims again to be sure?

Thank you so much for your help,

--Paul Elseth
Paul Elseth

The end float should not change with the grease. If you jack the car up and hold the top and bottom of the wheel you should be able to feel the float as you push and pull to wiggle the top and bottom of the wheel. The wheel diameter has the effect of magnifying the movement .You will not see the wheel move , but you will feel a definite float.Its difficult to tell the bearing drag once you have the brakes back on, esp as they rely on the end float to knock the pads back.It is important to have the torque right when you are checking the end float before greasing .
S Best

Once the torque has reached some relatively low level and has squeezed out any grease or rippling of the shims it shouldn't alter the end-float, that would imply one of the hardened pieces is squashing or stretching. If that were normal you would have to tighten them to 40 lb ft and then to the next hole every time you added or subtracted a shim. That would cause the torque value to be different each time, which would cause the end-float to vary each time, and so it would be nigh-on impossible to get the end-float right *and* the nut on a split-pin hole. Greased bearing will increase the drag very slightly, but as long as you still have the 'wobble' at the wheel rim ... and that isn't from worn king-pins or trunnions ... then you should be OK.
Paul Hunt

Yes, bottom line is there should still be 2 thou play when itīs torqued up and pinned, if not redo, not too hard if itīs disc wheels. Rich.
Rich

I have this same problem with a mgc front hub that I have for a 5 stud conversion,the bearing has not spun,it appears to be like this from the factory,I have tried new and old bearings and they are all a drop in fit.Oh and also the face where the disc fits is off, making the disc have 20 thou run out!

Dave...
Dave Lowe

I wish that people would stop repeating the incorrect information that hub end float or disc rotor runout are responsible for the retraction of disc brake pads.
A quick check of specifications will show that brake pad clearance is greater than the maximum allowed hub end float and disc rotor runout.
When disc brakes are applied the square (or rectangular) cross section piston seal does not move in the caliper cylinder but only distorts in shape. When the hydraulic pressure is released the seal returns to its original shape, giving the correct pad clearance.
The seal only moves along the bore to compensate for pad wear.

Mick
Mick Anderson

So how come that at a standstill, pressing and releasing the brake pedal leaves the disc still clamped, but not when the wheel is rotating and the steering turned back and fore?
Paul Hunt

Mick, I don't see how the rubber seal could carry out the strong spring function envisaged above. The seal is not anchored in any way to the piston . Also . if this was the case how is it that dragging brakes can be cured by cleaning up the pistons.
PS , I think you meant "move along the piston", the seals are fixed in the bore .
S Best

I expect the square seal could have some small springy effect but it is likely to be far less than the learance necessary to prevent brake drag (you have an itty-bitty area of "seal" to work with).

End-float likely causes some of the "retraction" as does rotor run-out. After all, the pads need not be far from the rotors, just a couple thousandths is plenty. If you do the math you will find that 2 thou multiplied by the distance to the edge of the rotor becomes about 5 thou (assuming a neat pivot about the stub-axle centerline).

Mike!
mike!

This thread was discussed between 07/02/2005 and 21/02/2005

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