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MG Midget and Sprite Technical - Front hub problem

Well I've put in the Frogeye pedal box (with modified pivot bolt Guy) and all the brake lines so attempted to install the front brake pads. The hubs were acquired S/H a while back and, apart from cleaning and painting, I have retained the original bearings (RM not removed from hubs). First side was fine. On the second, the outer pad is too tight. Looking at the hub thread on that side the nut isn't quite as far on as the "good" side, no thread showing. The calipers seem fitted snugly as does the disc. I'd cleaned the stub axles and wasn't aware of any burrs or edges. I thought it might be the caliper piston but it's pushed right in. So does that sound like the hub hasn't gone on to the axle enough? In which case, how do I correct this? Hub nut torque is correct, in fact I increased it a bit but the hub is pretty tight.
?
Bill Bretherton

If the outer pad is too tight doesn't that mean the hub assembly is too far onto the stub axle?
Rob
MG Moneypit

Rob
No, not on far enough so that the disc is too far out and too close to the outer part of the caliper. I've just realised this is probably all about FWB's......
Bill Bretherton

Other way round isn't it Rob? If the hub isn't far enough on, then the disc is too far out and the clearance between disc and caliper is insufficient to fit the pad. If I have understood Bill's description the disc isn't positioning centrally in the caliper gap.

If this is the case, the classic explanation would be that the inner bearing is wrong and doesn't have the 2mm radius chamfer on the inner race where it goes up against the root of the stub axle. This prevents the bearing seating properly and this could be the problem.

My guess anyway.
GuyW

...but Bill said they're original R&M bearings.

I assume they were fitted the right way round?
Dave O'Neill 2

Bill said they weren't removed.
But maybe they were wrong before as well?
GuyW

I didn't fit them Dave, never removed them. Could it be that the offending one is the wrong way round (inner)? Yet ISTR the writing on the bearings was showing on the inside of the hub for both hubs. Does that make sense?
Bill Bretherton

Bill, your right the amount of exposed thread should be the same on both axles.The hub is not seated far enough in.

A few thoughts
1] Are they RHP bearings?
2] Have they been correctly installed. The word 'thrust' on each bearing should face each other, ie you shouldn't be able to see it, you may have to remove the oil seal to check.
3] The inner bearing can be tight on the axle, thus impeding proper location. I have run a strip of emery around mine so the bearing slides sweetly.
4] long shot, but has the oil seal located. some of the early steel cased oil seals can need jiggling.

Bob Beaumont

Bill, I think I would measure the clearance either side, between the disc and the slot in the caliper. If the difference in the two measurements is around 4mm, suggesting the hub is 2mm too far out, then this would match the effect of a bearing that doesn't have the radiused inner race.

It is a check you can do before stripping down and may give a clue.
GuyW

Correctly fitted, the side of the bearing that you can see should look like the first photo, with a thin outer race and a large radius on the inner race.

If it's the wrong way round, it will look like the second photo.




Dave O'Neill 2

Bob, Guy, Dave
Thanks, lots of useful information. I'll measure tomorrow, as you say Guy, and proceed from there.
Bill Bretherton

Bill,
wow, I almost replied first with FWBs but thought it best to see what others think.

If you want I have lots of info I can send you about FWB, much from he who cannot... but also much of my own findings with thanks to a mate with access to an engineering shop.

I had problems about Feb(?) last year but the thread as usual got long and convoluted, not helped by me, but my (corrected) end conclusion was correct.

Do NOT follow Norm Kerr's drawings popular on the web and MGExp as there are errors.

If you want info sending just let me know.

I've recently put in another thread (Tim's) about Meditech bearing kits.

To start, backing DaveO, here's an LS photo showing writing to centre (spacer obviously missing for illustration of bearings facing).

And an LS photo showing sides to bearings without wording stamped on them.





Nigel Atkins

Yes, not far on enough. It doesn't pay to give advice late in the evening after a few Chinzanos!!
So I think others have given possible reasons.
It does sound like a classic FWB problem. Maybe inner replaced with non original bearing? or bearing replaced singly so no longer face adjusted?
It will be an interesting soultion.
Rob
MG Moneypit

Bill,
the relationship (size of shelves to size of spacers) of hub to spacer is very important. Original spacers should fit original hubs, and the replacements hubs but if the spacers have been replaced for different ones or shimmed or shortened (perhaps to get the cheaper bearings to fit) or the hubs not perhaps machined exactly there can be problems.

Hubs and spacers have to marry up, then original bearings will fit well (within the tolerances) and possibly even the cheap bearings but with acceptable play or if your lucky fit fine.
Nigel Atkins

Problem solved and I owe you all an apology! That'll teach me to do "one more thing" at the end of the day.

When I looked at it in the morning sun and with a rested brain I realised that the disc offset was very slight and there must be more to it. Also the castellated hub nuts weren't very different really. So I removed the caliper and sanded smooth the mounting surfaces (again, just to make sure) but noticed that the outer dust seal retaining ring was slightly proud in one place. I remember having trouble fitting them a while back (with new pistons). So I pressed it in, replaced the caliper and the pad will now slide in. It picks up a little on the disc and is a bit tighter than the inner pad but is acceptable. Once the pads have bedded in all should be well.

Thanks everyone, the bearing information is certainly useful for me as I've never fitted them.
Bill Bretherton

Good outcome Bill.
Better than having to read through a 550 message fwb thread!
GuyW

All's well that ends well.

The thread I started wasn't 550 messages, but no doubt it was overlong, repeating a lot that came before.

I forgot to say others on here help me too with advice and pratical help too.
Nigel Atkins

Nigel
I can drag it out a bit more if you want ;-)
Bill Bretherton

Bill,
we can drag it out if you want, indeed we have, I was referring to the thread I started last year, and opposing it to reading the 550 thread.

Oh, just realised you might be referring to dragging out the thread I started last year, or the 550 - no please don't extended either of those!
:)
Nigel Atkins

This thread was discussed between 24/04/2020 and 25/04/2020

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