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MG Midget and Sprite Technical - Rear brake shoes

Rear brake shoes - not just any old brake shoes but specifically the use of the wider mini front shoes in place of the standard, narrower Spridget rear ones.

The new shoes that I have are very slightly longer than the ones I have removed. The curved ends of the shoe that rest against the piston and against the adjuster tappets are just a little longer - about 1/4" in total. The result is that with the adjuster wound right out the drum will just push on but is dragging heavily.

Is this normal with using these shoes? And is the standard solution to grind a little off the ends of the shoes? Or should I drive for a bit and see if they centralise better or bed in? Anyone else with experience of this?
Guy W

My understanding is you have to grind a little off...no experiance here
Prop and the Blackhole Midget

Thanks Prop. I put it all together and went for a run arountd the block (in the car, not on foot) to see if that would settle the shoes. It did a bit but the drums are still way too hot, so I think some "adjustment" with a file is needed tomorrow.

Annoyingly although the shoes needed replacing anyway, I had hoped it would solve The Annoying Noise. Actually its more than annoying. When braking, I get a dub, dub,dub,dub noise. It is at wheel rotating frequency I think. It seems too slow for prop shaft. And it's only when I brake, and I can feel it through the pedal as well. Front discs and pads are fine (I just checked) I assumed it was the old shoes which were nearly down to the rivets (only they are bonded)but with new shoes, cylinders and backplates the noise is still there! Perhaps it is a UJ, but why only when I brake?

Wheels coming off again tomorrow to file the shoes and have another inspection.
Guy W

drums out of round would be first port of call for that noise IMO
Rob Armstrong

Thanks Rob, yes I guess so. Would also explain the feel through the pedal. Something to check for, though they looked fine and I didn't notice anything when I cleaned them up before fitting the wider shoes.
Guy W

I found it very hard to tell if one was out other than by feel, had one egged on the Landy, a front one, dubdubdub with light braking and wobbly with heavy. Looked OK though!
Rob Armstrong

I've got mini front shoes on too Guy, I think a certain amount of easing was required. But it can't have been much or I would expect to have remembered...

Can you take the drum off and turn it outside in, then lock it down with the screws and use a piece of chalk lightly touched against the inner face while it rotates

You might get a sight of any eccentricity that way

Som of us have been known to let the engine run with the back jacked off the floor and axle-standed which lets SOME runout become visible as the axle turns in sympathy

Not an easy fix unless you buy new and get the new drums checked for runout in a lathe


:-(
Bill1

I will try that reversing the drum, Bill. Neat idea!
I think I may have some spare new drums somewhere. Just need to find them!
Guy W

just a thought

back the shoes way off,so they are IN-effective and drive down the street....if no noise.. you found the Issue....if there I still the da da da sound, keep looking
Prop and the Blackhole Midget

That's too simple, Prop. The shoes are already backed right off and still binding because of the longer Mini shoes l am using.

But I could remove the shoes and tie-wire the cylinder pistons and try it like that, one side at a time.
Guy W

Well I have messed with it some more, but still have the Annoying Noise.

I disconnected the handbrake cable and then got the brakes to back off nicely, now they adjust up properly. Locked, and then three flats back on the adjusters and they turn freely with no drag. Reconnected the handbrake, properly adjusted this time. Handbrake locks them up tight on 5 clicks.

Road test and works fine except the noise is still there under braking. Swapped out one brake drum (I only have one spare). Noise still there, so swapped it over to the other side. Noise still there. Tried running in gear on axle stands, which is always exciting! A fair bit of shake rattle and snatch as usual. I don't think that under braking the Noise was still there but it may have just been masked by the other noises. But I couldn't feel it through the pedal as before so now I am wondering if it is a warped front disk!

I think a warped front disk shows itself up by the pads being kicked clear of the disk more than normal So if driven and then stopped without using the brakes, the front wheels spin with pads well clear of the disk, rather than just lightly scuffing as they should. Probably easier to simulate this with the front wheels jacked up and spun by hand.
Guy W

Well spinning the front wheels was inconclusive.
Time (tomorrow) to break out the DTI and magnetic base!
Guy W

Guy,
have you still got those Green-Stuff pads, I was thinking of what happened to Rod's

as I remember it you were happy with your car's braking performance and have the shoes running loose* so I wonder why you've decided to beef up the rears now

*yes I do realise this doesn't really effect overall braking performance of even the rear brakes other than the fraction of a second delay in application
Nigel Atkins

Hi Nigel,
Just decided to go for the wider rear shoes as they needed replacing anyway. Plus I needed to sort out a failed backplate adjuster and the mysterious noise! So a good time to upgrade. I have greenstuff on the front so I think a slight improvement in the rear may help the balance a bit more. Brakes have always been good on this car, other than the fairly recent addition of The Noise.

I don't think I ever said that I had the shoes running loose. Perhaps you misunderstood. What I believe I was talking about ( but it may have been in a different discussion) was that I tightened the shoes up a notch or two for the purposes of the MOT, so that they came on fully sooner. Tightening the adjuster has no effect on measured braking efficiency, but does give a bit of added confidence as the brakes come on with less pedal movement which I think impresses the MOT tester! The downside is that this meant they were dragging a bit so after the test I would back them off again to their correct setting.
Guy W

Guy... I think you answered the question...with the shoes inactive and still bump bump bump...its not the rear brakes

If it only does it on braking its got to be in the front brakes, or an issue with the master cly / proportioning valve...perhaps a worn out ovaled clevis pin in the peddle assembly

Did you check that the rear suspension is good and tight the leaf spring bolts havent worked loose... a quick hit with wrench wouldnt do any harm...I know they do like to work loose and sound like a bad UJ

Prop
Prop and the Blackhole Midget

Prop, I did check all the suspension bolts, but only because it was up on the axle stands so it was a good opportunity! Noise does seem to be wheel related in frequency. And the fact I can feel the pedal pulsing must mean it is brakes.

As I knew the rears were due for a rebuild (new back plates, brake cylinders and brake shoes) I sort of assumed that was where the noise was coming from and disregarded the front disks. But now its beginning to look like it cannot be anything else!
Guy W

Guy,

As you have tried the most likely, might be worth checking the tyres for sidewall and tread bulges.

R.
richard boobier

Guy,
I was thinking of Rod's green stuff pads surface badly breaking up and pitting, we never did find out if they were counterfeit, very old stock or what might have caused it

yes I misunderstood on the rear brakes, I thought you meant you had a little bit of play on the pedal, or that's how I wrongly remembered it, I've got it now but will probably forget again

if it's at the front we all know what it could be but are afraid to mention it :D
Nigel Atkins

Nigel,
The unmentionables at the front are OK! I know they are as I checked when I fitted and reamed new king pin bushes a few months ago.

Richard, I will check for bulges, but I have had the rear wheels off and on again so many times in the last couple of days I think I would have noticed any bulges. And although they could make the Annoying Noise, I don't see how it would translate into throbbing through the brake pedal. but you never know.
(Incidentally, Richard, I was down staying with Greg last week - remember he who passed that homeless Dalek over to you)
Guy W

Guy,

Have had a tyre on a B give a rythmic vibration - an out of round egg size distortion on the Tread ! and it was a good quality tyre.

If you come this way let me know - I'm only up at Clevedon - Junction 20 - about 1 mile from junc.

R.
richard boobier

Id give that clevis pin a looksy next

that connects the master to the peddle, my clevis for the clutch got oblonged egg shaped and it did some crazy things like vibration and poping

Its an easy check

Next would be to pull the brake hubs fix them in a gig and test like bicycle wheels for true

Then check For a loose caliper

Prop
Prop and the Blackhole Midget

Update,
Took the car for a bit of an Italian Service and the pedal throb and Annoying Noise does seem to have reduced a bit. But it is still there and it aint right.

Tried a Dial gauge on the front discs to test for warping. O/side has 0.001 to 0.0015", which I would say is pretty good. N/side a little more at 0.003 to 0.0035". Without the noise and an odd mark on the disc I would have said that was within tolerance OK too. ( ? )

But there is a line across the face of the disk, a cord, with what seems to be slightly pitted steel to one side of it as, if it had been immersed in water, but it hasn't (new disks fitted about 25K ago). Pitted area just registers on the dial taking it to the max 0.0035 figure, but only 0.001 greater than the adjacent bit of the disk so it is hardly a step that would cause the calliper piston to pulse.

So verdict? Should I replace it? Is this likely to be the cause of the noise problem? Or do I keep looking elsewhere for the noise? Answers on a postcard. . .
Guy W

Guy,

Some time ago an automotive machinist told me that bad metallurgy in brake discs (like slag inclusions, hardness irregularity, etc.) can give a feel similar to that of a warped disc. IIRC, I think he said it was even more common than warped discs. Maybe that is the problem with the disc you describe.


Charley
C R Huff

Guy,
I'm you've already done it but just for a sanity check, how about taking out the front pads check the surfaces are smooth and check that no foreign bodies have got in to ensure they're seated nice and true? I can't see how they wouldn't be though.
Matt1275Bucks



I cant say one way or the other with any certainty, but at .003 to .0035, thats right there at human hair and dust thickness on my book shelf....

my gut says no, its a none issue

Did you look at the clevis pin yet at the master and peddle arm....actually pull the pin for a look at the pin and the pin hole Its self.

Prop
Prop and the Blackhole Midget

I forgot to post the photo of the said disk!

Charley - yes that is what the line looks like it might be. Perhaps not a slag inclusion, but a change in the steel. At the price that discs are these days (=cheap) I wouldn't be at all surprised if that was what the mark is. Just wasn't so sure that it would cause the pulsing noise. But if its a fault in the disk I maybe should change it anyway, before it shatters at an inconvenient roundabout approaching moment!

And Matt, yes I checked the pads. No embedded crud, smoothly worn with a Matt finish so they must be OK!

Here's the photo:


Guy W

Is that after the Italian Tune up? Get a new disk on there IMO, looks odd. Could be that the 'different' bit warms up differently and that'd giving you the pulsing.

Rob Armstrong

Wow....ive never even heard of that before let alone seen it

Im with rob....change it out, that just isnt kosher...im sure rob is onto something, it probably does heat up at a differant speed then the rest of the hub

Put a gyger counter on there, id be curious if its radio active, our idiot republican party politians approved using radio active scrap metal, several years back for everday items esp. car parts to help business be more profitable

If it came from over seas.... id say theres a good chance your nuts are sterile

Prop
Prop and the Blackhole Midget

Guy,

The disc in that photo looks pretty suspect to me. I don't know if discs go through a heating/quenching cycle, but if they do, maybe some of that disc missed the quench bath.

Charley
C R Huff

Any chance it got Over heated then immediatly parked in a pool of water

It really does look like 2 separate metals...

Id call the "manufracture" and ask ...hey, whats up doc

I can see that thing exploding with just normal braking

Prop
Prop and the Blackhole Midget

Changed.
I just happened to have a pair of new spares in stock.

That one had been on the car for something like 3 1/2years / 25,000miles. Certainly didn't look like that when I fitted it! I noticed the line a few months ago and thought at first it was just the print from the pad as it had been standing unused for a week or so when I first spotted it.

I think it is a flaw in the steel. It doesn't go right through, at least it doesn't show a line on the other side like that. But directly opposite on the inside of the disc is an area where the steel is rough and pock-marked, rather than polished like the rest of the disc surface. So now I am hoping that has solved the mystery noise!
Guy W

fingies crossed mate

That disc looks awfully 'orrid to me, I think Charley might be right.

Looks like it had different treatment to the "real ones"

Bill1

Can't remember where l got them, but it would have been one of the usual suspects. Not from an unidentified e-bay supplier. They looked fine when new so it may just be a random fault. Are they cast iron, then machined?

I will try it out in the morning. Only reason it didn't get tested tonight is that I painted the hub part of the new disc, so the paint needs to dry overnight.
Guy W

Well, this morning's test drive enables me to report with great pleasure that the Annoying Noise is no-more!

Nice smooth brakes. The new shoes will need bedding in and readjusting but operation is all that it should be - or better!

Photo shows the odd line across the disc face on the outside, and bellow that the inside face with the pitted damaged area directly behind this suspect crescent.



Guy W

you'll have had areas of grip-no grip on that disc

nasty
Bill1

I dont know... think of that huge missing chunk as just brake ventilation

Hahaha

Prop
Prop and the Blackhole Midget

Poor man's antilock brakes, Bill!

Despite the mark across it, there was no indication that the piece was about to fly off on its own. But the steel is definitely of a much lower quality, hence the pitting and corrosion on what was bright polished disc when they were fitted. And the car has never stood unused for more than 7 days at a time in all the time they have been fitted, so l don't think a lack of use has anything to do with it.
Guy W

Good grief that's a little alarming. Definitely something wrong with how it's made I would say.

Suggest everyone goes and checks their disks, I know I will be tomorrow.

Glad the Annoying Noise has gone though :) That's one less!
Rob Armstrong

I have never thought about this before, but I don't know how these are cast. It's almost as if the thing is cast in a mould that is stood up on its edge - as when fitted to the car. And in this case there was insufficient molten steel so he had to go fetch another crucible full. Only he got distracted and went for a tea break instead! And then it was topped up with the leftovers from a different mix.??
Guy W

Guy,

If you know who made them, they might be interested to see it for quality control review.

Charley
C R Huff

Charley, I now have no record of where I bought them, some 3 1/2 years or more ago, so cannot report back on that, otherwise I would!

Car went for its MOT. Brakes came up fine. In fact they came up very good with a front brake reading of 95% which the tester was quite impressed with. He said that some modern cars barely exceed 70%. Hand brake was only 40% but that was fine too. He said they were all good considering I have only travelled about 3 miles in total since fitting the new shoes so they haven't bedded in at all yet.

Bad news, more of an annoyance than a problem, is that it failed on a lighting fault. Brake lights OK, indicators OK, but brakes and indicators together and the brake flashes in sympathy. It will be a poor earth connection, probably a bit of corrosion. Shouldn't take long to trace and a good time to polish up and waterproof a few of the electrical contacts anyway before the winter.
Guy W

That sucks...did they still pass it ?

I couldnt get my left side brake to light up, after several hours I said screw if and piggy backed the right aside and left side brake lights togather off the left side.. and clipped all the brake wires on the left...its still working as far as I know

Prop
Prop and the Blackhole Midget

Another case of our common language having different meanings, Prop? In the UK if the car fails the test, it doesn't pass!

But its not a problem. Just a task for tomorrow to sort it out and then take it back in on Monday morning for a re-test.

I actually like taking the car for its annual test. I get to look over the car in detail, in a logical sequence, with a knowledgeable professional to discuss what is acceptable, what is good and what may need attention. I get to walk around underneath the car for a proper inspection and its an interesting and worthwhile experience. Even when it fails!
Guy W

Honestly... I just scanned over ....with the good news I was assuming it was one of those warning notices that still passes mot you guys get from time to time....I least I was hoping it was...but yeah I guess a flashing brake light wouldnt be a good thing

Yeah...its just the hassle of it....but Im sure your right, about It being a grounding issue

.
Prop and the Blackhole Midget

Added an extra earthing cable to the rear lights and now all working as it should. Took it back in this morning to collect my MOT pass certificate.
All good for another year!
Guy W

This thread was discussed between 24/09/2013 and 30/09/2013

MG Midget and Sprite Technical index

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