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MG Midget and Sprite Technical - Rear hub carrier movement

Hi, Mk1 midget. I have an oil leak between the hub bearing carrier and the half shaft, removed the half shaft and will clean surfaces and fit new gasket and ‘o’ ring but I’ve found the carrier moves towards the back plate and catches on the brake cylinder! Pulling it forward it clears ok. The hub nut is tight. Why have I this movement please? Hope someone can help. Thanks
Tim Pollock-Gore

It sounds like you have excessive play in the bearing.

When the hub is moving, does the inner race move on the axle, or is it just the outer race.

Or, is the outer race moving in the hub?
Dave O'Neill 2

Assuming the bearing itself is the right one, and not some random 'slim line' oddity, the other possibility could be that the backplate isn't properly located / fixed to the axle casing. Does it feel secure?
GuyW

I think the right rear bearing (or hub) on the Frog is moving on a left hand bend. I've done about 90 miles today on the local classic run and could hear a noise temporarily on LH bends. No oil leak (presumably because the half shaft is clamped to the hub) but I seem to remember one of the bearings not being an especially tight fit on re-assembly a while back. I think the carriers can wear such that the bearing isn't held firmly enough and so moves laterally (or the hub moves). Something to investigate.
Bill Bretherton

Some have worn hubs.

The halfshaft flange, and the hub face, are the two halves of a sandwich. The bearing is the filling. It should be clamped in tight, as well as being a tight interference fit in the hub.

If either or both, the rubber o ring and the paper gasket are too thick, and the hub is worn, the bearing can move in and out of the hub as Dave said. It's a press fit, but if the hub's worn from the bearing not being clamped properly, it relies soley on the clamping sandwich.

I wonder if the outer race of the bearing could be sleeved. A sleeve inserted into the hub, and then the bearing pressed/driven in.

Is there a sleeve in the size of the outer bearing diameter?


anamnesis

I always use loctite on those bearings.
Getting the dual function of oil tightness and bearing clamping just right always seems a bit uncertain, even when aware of the issue.
GuyW

I'm still not certain what can happen without close inspection. IF the outer race isn't tight enough in the hub then presumably the hub could potentially move slightly inwards (driving round a corner) and touch the slave cylinder, or would the brake drum catch the backplate first? BUT, wouldn't the half shaft flange prevent inward movement as it's clamped against the outer race? Surely the bearing itself cannot move as it's inner race is clamped to the axle? Have I got that right?
Bill Bretherton

Bill,
AIUI the inner race is fixed solid to the axle by the large nut being done up tight.
The outer race is pressed into the carrier and with the gasket and half shaft clamped tight together by the wheel studs / wheel when the Road wheel is tightened.

There is only a very small movement in / out with the ball bearing tolerance in original set up.

If the carrier / bearing interface is not tight or clamped correctly, the bearing can rotate within the carrier - making the situation worse. I haven’t seen wear move the bearing in/out significantly when it’s all done up tight. But wear is likely to cause oil leaks etc as the wheel bearing moves about and could I suppose let the wheel a bit of wobble in extreme cases.

Mine was not as tight a fit as I would have liked and I put a few punch marks into the circumference of the carrier (iron) which took up the tolerance.
There are as Guy noted special bearing retainer adhesive that can be used - both of these methods are no use if had carrier is as well past it due to bearing spinning etc.
richard b

Thanks Richard. I'm guessing that if there is significant wear in the carrier then there would be enough lateral movement, albeit slight, to catch the slave or backplate as clearances are slight anyway.

Hope this is helping Tim!
Bill Bretherton

I would have thought that providing the screw holding the halfshaft to the carrier is up tight and the drum is also screwed up tight then the carrier can't move even if the bearing is slack in the carrier housing. Certainly I have a bearing that is slack in the carrier but there was no movement once all was screwed tight. Any movement surely can only be the bearing either worn or not tight on the stub axle.
I try and snug up the screws as tight as possible by using the wheel nuts bolted to the drum (with spacers)to clamp it all up and then retightening the drum and half shaft screws. Also helps to minimise oil leaks
Bob Beaumont

No one else seems to be considering a backplate issue? Not located correctly, or slack bolts? Or maybe it is damaged, buckled?
GuyW

Guy, agreed. A misaligned backplate could place the brake shoes and/or slave cylinder too close to the drum and the backplate/ drum clearance too small.
Bill Bretherton

With the half shaft removed, If the hub can be pushed in/out it means the bearing is loose in the hub allowing it to move.
The bearing is 'normally' a tight fit in the hub.
It's important to make sure the correct thickness gasket is used to clamp the bearing,--If the gasket is too thick the bearing can move in the housing and will eventually get to the stage of being loose enough to slide in there--which I suspect is the issue here.
If it's not badly worn the bearing can be seated into position using-'Loctite-Press fit Repair'-It comes in a little tube which will be plenty big enough for the job.--Make sure the bearing is right in.--wait for it to set.
Then--assemble it up and fit the halfshaft without a gasket and measure the gap 'feeler gauges' to determine the size gasket you need---exact same size as the gap or a thou or two less is the gasket thickness you'll need for a new gasket, if reusing an already compressed gasket go for a couple of thou---No sealant required as the O ring should seal it up----If it's real early and there's no O ring then sealant will probably be a decent choice.

willy
William Revit

I think I've identified the problem with mine. On original reassembly, I had a problem with one brake drum touching the backplate and started a longish thread about it. I'd fitted later 1275 backplates to the Frog quarter elliptic axle (so I could have twin 3/4" slaves) which caused the issue.

Richard turned down the inner edge of the brake drum on his lathe and it seemed ok. However, I think it needs a tad more removing.
Bill Bretherton

Well you know you only have to ask !

A trip to the seaside !

R.
richard b

Thanks Richard, that's very kind of you.
Bill Bretherton

This thread was discussed between 29/06/2024 and 03/07/2024

MG Midget and Sprite Technical index

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