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MG Midget and Sprite Technical - Rear axle seal & bearing questions

Hi

I have a 1961 Mk1 midget which has had various undocumented upgrades and bodges over the years.

Measuring the rear axle and halfshaft, it's a standard wide axle despite having wire wheels. Ie the wheels stick out a bit further than they should. Not an issue as the wheels just fit under the arches. I can see from past invoices that someone tried lowering the rear (quarter eliptic) then reversed that because the tyre rubbed. Not part of the question but just for background.

Putting my Midget in for MOT it failed on two things one of which was the rear right brake not working. Stripping down, the brakes & drum are covered in axle oil so the rear axle seal has failed. I've just stripped everything and, other than a bit of blue hylomar type sealant, nothing looks wrong or worn.

The bearing I've just removed from the axle is sealed both sides so non standard but perhaps a good upgrade? I can feel absolutely no play in the bearing and am tempted to put it back despite having new standard unsealed bearings ready to go. The seal isn't visibly ripped or worn and the metal where the seal lip interfaces has no wear grooves. Ie looking at everything I can't see an obvious point of failure....

Other than fitting new bearing and seal, new brakes and re-assembling everything plus doing the same on the other side of the axle, is there anything else I should measure or do? It disturbs me not to find an obvious leak source.

Also, is a sealed bearing a better idea than the standard unsealed? I could always get new sealed bearings to rule out bearing play and have the better thing if that's the case. Back when I had a an RE Bullet, it was an upgrade to use a sealed bearing with the seal removed from the inner side of the gearbox to allow you to use oil rather than an oil-grease mix. The standard open bearing would leak oil and in the old days the oil grease mix would lubricate the gears and bearing without leaking too much. So I wonder if something similar is a good upgrade in my axle.

Thanks



P Peters

I'd say there is nothing wrong with your bearing; Sealed or not.

You don't really need sealed bearings here. Open bearings get lubed by the diff oil. Sealed by pre greasing.

The original open bearings pretty well lasted for the life of the car. It's only because so many Spridgets have lasted way beyond their expected lives that the rears eventually give up. I didn't replace my rears until way beyond 200k miles; probably 300k actually.

Your oil leak onto the drums is due to the halfshaft O-ring, or gasket, or both failing.

A New **CORRECT** O RING AND GASKET will fix it.

If all else fails, copious sealant on the half shaft and hub faces. But the correct size/thickness decent gasket and o-ring is preferred by me.

anamnesis

Thanks Anamnesis.

I've got a kit of gasket, O ring lip seal and bearing from one of the usual MG suppliers ready to go. I didn't want to do the job only to find I hadn't spotted something and end up doing it again in 6 months.

Would you pre-emptively do the non-leaking other side? I'll change the brake shoes on both sides regardless so they both have even wear. I'm inclined to do the bearing while I'm at it since I bought the socket and want to use it more than once in my life :)



P Peters

I'd suggest measuring the axle end to ensure the diameter on which the lipseal runs is within spec. This is a long shot, as in my experience if it looks good it usually is good. As Anam says, there is so little that leaks here that a new gasket and O-ring will almost always be enough. If it isn't, you are most likely looking at a speedy sleeve on the axle.

You might use the hub nut spanner more than you expect. You'll need it if you have a broken half shaft or need to rebuild the diff.
Les Rose

On my frogeye I used sealed rear hub bearings with one seal removed from wet side. But only as it was easily done anyway.

Getting a good hub seal does depend on using the correct paper gasket. It's a balance between compression of the gasket and grip against the bearing outer face to stop it spinning in the hub. I would use a little locktite bearing seal as well.

Check also that the axle breather is clear. If it blocks then as oil heats up it can cause leaks.
GuyW

If you're going to do the nearside too, don't forget the hub nut has a left hand thread.
Dave O'Neill 2

A long time ago and early in my Sprite ownership I decided to undertake preventive maintenance and replaced the rear axle bearings with new ones. There was slightly more play with the new bearings than the old ones.

It's worth taking a close look at wear the oil seal in the rear hub runs on the axle to see if there is a clean surface and no slight channel. If there is a poor surface or channel than it's not that difficult to fit a speedy sleeve.


Daniel

Thanks all.

Axle seems clean enough both sides to not need speedy sleeves. I have one side done and the other stripped ready to re-assemble but the kit only had one lip seal. Hey ho. At least I know how to do the rear brakes, hub bearings and change a halfshaft on a Midget now. I think I might have done this same job on my Morris Minor back in the '90s

Frustrating that the axle is that inch too wide. The rear could do with being a bit lower but there isn't room.

P Peters

You might want to look in the archive for issues with wire wheel half shafts in a steel wheel axle as it doesn't give much engagement in the sun gears in the diff IIRC.
David Billington

It's a standard 948cc so shouldn't be too stressed but if I wanted to prevent that is there a size of standard or upgraded halfshaft that would resolve this?

Thanks
P Peters

The wire wheel axle is slightly narrower. It was NOT an option for 1/4 elliptic sprung cars only available from the semi elliptic sprung cars. You could get a later axle converted by having the brackets etc welded on but quite a challenge!
There was a conversion for wire wheels offered for the early axle as fitted to the sebring Sprite. It uses the original back axle but different hubs
Bob Beaumont

Peter May does longer shafts which when pressed into the splined hubs give the correct length for use in a standard steel wheel axle casing.
David Smith

According to Horler's OS&M, wire wheels were an option on quarter-elliptic cars from GAN2/HAN7.
Dave O'Neill 2

There was (still is?) a conversion kit that retained the original disc wheel axle and halfshafts, and had the hubs bolt on to the drums, so didn't have the half shafts pressed into the hubs as in factory-fitted wire wheel cars.

If that's the case, then the halfshaft should have the right engagement. If in doubt, you could check by measuring the witness marks on the splines.
Paul Walbran

Speaking of half shafts, --

How do you store your spares?

Laying horizontal, supported along the shaft?

Or hanging vertically?



anamnesis

Anybody?


anamnesis

I think my two are just laying on the garage floor but on some old vinyl sheet. But they're the older weaker ones so wouldn't be used long term, just as a stop gap if needed.
Bill B

Does it matter ?
Mine are in a cupboard under a bench.

But what I consider most important is to mark which side they came out of I.e near/off side to avoid winding them up against the direction they have been driving previously and potentially causing stress issues and more likely failures - obviously they do rotate the other way when reversing but usually not so spirited driving to cause an issue !
richard b

I agree about the rotation.

But I was also wondering if they could be deformed/'bend' slightly, if not supported over a long period of time unused.

Hence my question. Is there a 'correct' way to store them?

Until now, I've laid them flat. But maybe they can't 'bend' under their own weight anyway.





anamnesis

Anam,

Steel doesn't suffer from creep https://en.wikipedia.org/wiki/Creep_(deformation) under any conditions you're ever likely to encounter in your spridget or shed. Lead can creep under ambient conditions which is why the length of lead runs is limited in roofing or it will creep under its own weight if too long.
David Billington

Ok thanks David. Then I'll just keep them stored in the most space efficient way.

anamnesis

Just to update on this, having fitted everything and put back together I noticed a lot of wobble on one of the wheels. I dismantled slowly and found one of the _new_ bearings from a reputable supplier has quite bit of play:( Certainly more than the old sealed bearings. The other bearing has a bit of play - more than the old sealed ones. One of the sealed ones graunches so I'll replace both for peace of mind.

Before anyone says, I didn't whack the outer to fit the hub onto the axle or the inner to fit into the hub anything else that would damage the bearing.

I'll try again using the bearing number from my old sealed bearings to replace like with like.

On the plus side I've got really quick at dismantling and reassembling hubs :/ Plus I discovered that many torque wrenches including mine don't measure torque anti-clockwise! I thought I was getting weak in my old age.

Is the attached image a hardened halfshaft? This is my R/H halfshaft. The L/H one has no groove.











P Peters

That is a stronger halfshaft, from a 1275 - part number BTA806.

One of your original halfshafts probably broke, at some point, and it was replaced with this.
Dave O'Neill 2

P Peters,

I expect you were feeling the wobble in the hub without the halfshaft in place and some is to be expected. IIRC the bearing is a standard 6207? deep grove ball bearing so can be sourced from many places and I would likely buy an SKF bearing but there are other quality makes. It's such a common bearing that buying quality doesn't cost much more than cheap. The axle is a semi floating design so the bearing provides mainly axial location and the halfshaft takes the bending due to cornering. You shouldn't feel wobble with the half shaft in place and clamped solidly.
David Billington

Thanks guys.

FWIW there was wobble in the wheel when all was put back together. I thought I was finished...

I've ordered Timken bearings. Certainly not much difference in price between cheap and quality


I looked up BTA806 and it shows a shaft with a 'hat' at the end which seems to be one piece. Does the hat come off or could it be BTA807 for wire wheels which I have albeit on a wider non wire axle

P Peters

Sorry. Yes, I forgot you had wire wheels.

You only showed one end of it ;o)

BTA807 it is.
Dave O'Neill 2

And the image earlier of the spline end of the halfshaft shows shorter than normal spline engagement from having wire wheel shafts in a steel wheel axle casing.
David Billington

I don't think there's a solution to that that isn't expensive with the cheapest option being to keep a spare half shaft.

I know a good welder who could cut and shut the axle. Not keen on messing with all the crownwheel gubbings what with setting resistance and god knows what. Looking at the design it seems I could just remove the diff whole without dissassambling. Is that correct?

Actually looking on Ebay just now there are a few wire wheel axles. Do they bend or break much?







P Peters

P Peters,

The whole final drive unit comes out of the axle casing after undoing 8 nuts and pulling the halfshafts, no need to mess with the final drive/diff internals at all. It's likely you'll be fine as is unless you drive it like you stole it. I read some comments online about it and they seem to last like that without issues. I've only heard of axle casings failing when excessively rusted.
David Billington

We did have the axle housing that put up with the supercharged K for a few years decide to surrender, cracks ran all over it from the spring mounts. Made it very wandering!
Paul Walbran

Rust is the main enemy but in the day I did have a casing fail on my Minor - similar casing (big wheels etc etc).
Did a bit of a boy racer handbrake turn and heard a very loud bang but couldn’t see anything wrong.

Following day went to Woolacombe beach and parked on a slight slope. Came back to find some oil by a rear wheel. Climbed under and found a crack by the spring mount over the top half of the casing and running along the centre weld towards the diff for about 6” - drove home about 60 miles very very gently and trip to scrapper for a new axle- loads about then !
richard b

Thanks

Looking in more detail on Ebay, it looks like the narrower wire wheel axles are out there but not for the Mk1 with quarter eliptic fittings.

It's easy enough to grind off the half eliptic fittings but perchance does anyone make fittings for quarter eliptic springs onto stripped later axles?

I guess I could transplant the fittings from the 'wrong' axle but I don't want to keep the car out of action much longer. Having a spare to prepare at leisure seems the better option.

On the other hand at nearly 60 I'm starting to find it hard to squeeze in and out. Not really a question, more the is it worth the effort if I can't enjoy the Midget in a couple of years

P Peters

Nearly 60? You're a mere youth 😏
Bernie IIRC is in his 80s and some/most of the contributors here are in their 70s so to answer your question - yes it is worth it if you're still invested in the car.
A smaller (even an inch) steering wheel can help as it gives just that bit more space for arthritic knees/dodgy hips etc to be able to articulate!


Jeremy MkIII

Actually have a removable steering wheel which helps a lot
P Peters

Just to update everyone here, I finally got everything back together and the car ready to go back for MOT.

I'll keep an eye out for a suitable axle casing in the meantime. It would be nice to be able to lower the rear slightly.

The other thing I had to do was fix the front anti-rollbar. It had started to rip the mounting out of one of the front members. I've cleaned it up, welded it back in place then added a plate over both front members with a slot for the anti rollbar mounting.

Unfortunately I didn't take pictures. Anyhow the plate is plug and edge welded and hopefully will stop that being a problem in future. It's based on advice from the archive here.

Next job, changing the front screen which is scratched plus all the petrified rubbers. A quick check with the correct screwdriver reveals it will be a job getting the frame off the body. By the look of the rubbers it hasn't come off in 60 odd years.

Oh and just to vent, who's the b*&*d at Castrol who decided that the plastic tube that comes out of the gear oil spout should be widened so it no longer just fits in the filler hole in the diff? My answer was to use an old soap pump thing I used to top up my Vespa gearbox except the straw-like tube fell off into the diff before I could catch it. So much time with a grabby claw and bits of bent wire before I finally extracted it out of the bottom plug.



P Peters

The usual way of lowering a 1/4 elliptic car is the fit wedges under the springs like https://www.petermayengineering.com/product/1-4-elliptic-spring-lowering-wedge-pair/ . Those might be more than you want but give an idea of what you may have to get made or find elsewhere with less taper.
David Billington

David Billington, Lowering would be nice to do but a previous owner tried and found the wheels rubbed so reversed that. It's the wrong axle again :)
P Peters

This thread was discussed between 25/04/2025 and 25/05/2025

MG Midget and Sprite Technical index

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