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MG Midget and Sprite Technical - Issues with shoes or drums?

Hi,

I’m currently rebuilding my rear axle (‘72 midget) with new cylinders, shoes and drums. I’ve stripped and painted the back plates but have checked the drums don’t rub on the fresh paint when fitted without brake shoes.

As far as I can make out, either the shoes are oversized or the drums are undersized as when I have fitted everything the drums won’t turn on either side. Both adjusters are completely wound out. Unfortunately I don’t have the old shoes (or wheel cylinders) to compare, but when I refit the old drums they turn - albeit with some minor friction from the shoes.

My initial assumption is that the shoes are too big as the old drums are at least thirty years old so are probably worn - which allows them to spin with the new shoes.......... But it may be the old drums are the correct size and the new ones are too small.

I suppose my question is whether anyone out there has had this problem - either swapping drums, shoes or both. I’m thinking of getting another set of shoes to compare the fit but open to other suggestions.....

I’ve replaced the brakes many times in the past with no problems but that doesn’t mean I haven’t done something stupid this time - although for it to be on both sides i’m thinking it’s more likely to be out of spec parts.

Thanks in advance,
Dave
Dave

I've had to "relieve" the ends of the shoes before to get them to fit. IIRC the last time was the handbrake shoes on a Mercedes-Benz 300SE. Brand new OE spec and just didn't fit. I have the impression it's not uncommon, but others will know better than I.
Greybeard

Dave, did you centre the shoes on the drums?
Also, when winding the adjusters out do make certain that the adjuster is "parked" correctly so that the flats on the conical end are aligned to the wedge collets
GuyW

Thanks both.

Yes, i’ve tried centring the shoes by eye in several different places with no joy. Also, having had the old drums back on and turning, i’d have thought this would have aligned them.

The adjusters are out far enough that the collets are touching each other so the flats on the adjusters aren’t in play.

Will look at relieving the ends of the shoes tomorrow - if i’ve got to replace them anyway then there’s nothing to lose if I go too far.

The only saving grace is that the axle is on the bench rather than on the car......

Cheers,
Dave
Dave

Obvious, I know, but try stamping on the brake pedal a few times to centre the new shoes.

Shoes the right way round?
GuyW

Stamping on the brake pedal won’t make a lot of difference as it’s also on the bench with the axle. :o)

I’m rebuilding the car and am refurbishing suspension front and back before I start bolting bits onto the bare shell.....

I’m fairly certain they are the right way round - but as I said before, there’s no guarantee I haven’t done something stupid......will double check tomorrow.
Dave

OK, stamping won't work then will it!
Tried swearing AND stamping?


Seriously - its very difficult to get the shoes sufficiently accurately centred just by eye - stamping on the pedal is the best way. Or maybe on the bench a few strong yanks on the handbrake lever emerging through the backplate. Try a chord around the lever and tug on that.

It is of course possible that you are worrying over nothing, and it will sort itself out when assembled on the car and used.
GuyW

Thanks Guy. And, yes, when it’s all together it may be fine. But it’s far easier to work on when it’s on the bench so i’ll try all the suggestions and will hopefully see some improvement. If not i’ll leave the old drums on while i’m putting it all back together and worry about it later. Probably around the time I’m trying to bleed the brakes......

I’ve already tried the swearing approach with limited success. Maybe it wasn’t loud enough?

Cheers,
Dave
Dave

Fit the shoes and drums
Tighten the adjuster rock solid
Give the drum a couple of good whacks with a big hammer
Unscrew the adjuster

Shoes should be centered now.

It could help to give the leading edges a good chamfer before this
O K

Not necessarily part of your problem but also worth a look is to have the drums trued. Being new does not guarantee that they are round, concentric with the axle centerline or the same inside diameter. By having them size matched and rounded by a skilled shop will give you a little more room and eliminate the possibility of vibrations, pedal pulsations or pulling to one side when it finally hits the road. I've learned this thru some bad experiences with new drums in the past.
Stan Kowznofski

I had some new drums that were out of spec.Try reversing the drums on the hub and see if there is any play around the stud holes - mine had loades.Then try a dial gauge to check the runout.I ended up returning the new drums and reusing the old ones.
f pollock

Thanks all - will check the drums before I do anything more then will give all the suggestions a go. They all make sense- hopefully one, or more in combination, will sort it.

Cheers,
Dave
Dave

I had high spots in the new drums I bought, they're so cheap (ly made) to buy it was no surprise.

I was able to fit them and do running adjustments to wear them in.

Just to be sure of installation, I followed these illustrations (second to follow) and the rear brakes seem to work very well.

BTW I'm not sure all other illustrations correctly show the handbrake levers.



Nigel Atkins

T'other side -


Nigel Atkins

Well, with a combination of the above - but mainly relieving the ends of the friction material - i’ve got the new drums on and turning. There’s still an element of friction without the adjusters screwed in at all but i’m confident that they will sort themselves out once the car is back on the road.

Thanks again for your help and suggestions.

Cheers,
Dave
Dave

Well done Dave.
I have yet to find a Spridget where there wasn't at least a little scuffing on the rear shoes when correctly adjusted. If they run too freely then too much hydraulic fluid needs to be pumped to the rear brakes before they come on, and the consequence is an excessively long pedal travel and in some instance, the operation of the front calipers is compromised.

Light scuffing doesn't matter as the shoes will centralise that last little bit after just a few miles of use.
GuyW

This thread was discussed between 05/01/2019 and 06/01/2019

MG Midget and Sprite Technical index

This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.