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MG MGA - Disc Brake Squeal

Most of you will be aware of my previous MC problems which resulted in its replacement. One of the issues at the time that got me looking deeper into the problem was brake squeal from the front left disc.

Replacement of the MC cured all my braking problems, except for the b****y squeal.

To try to cure the problem I completely dismantled the entire left side suspension, hub, disc and calliper; rebuilt the lot. Centralised the disc to within a thousandth of an inch; copper greased the pads; but still the squeal persisted.

I spoke to Bob West who reported that others who had converted to discs using the recently available alloy MGB calliper adapter plate reported similar squeals. He suggested using a different compound to copper grease, citing a sticky/rubbery compound that Mercedes used a few years back.

I located a similar compound named Pro Seal - Disc Brake Silencer (Made in the USA). It seemed to cure the problem for about 5 miles, then the squeal returned worse than ever.

I was now at my wits end, but resisted throwing anything around the garage. Instead, I looked very closely at all the shiny contact points on the pads. It was then that I noticed bare metal contact points on the pads and the calliper. It was the leading edge of the metal part of the pads where they contact the calliper front wall when brakes are applied. I applied copper grease to these contact points and an extra layer of the Pro Seal compound where the pistons had pushed through compound to the bare metal. I let the compound set properly this time for about half an hour, then reassembled. Hey presto, no squeal. Peace in our time. The only problem now is that I do not know whether it was allowing Pro Seal to do its job properly, or the copper grease on the newly identified contact point that solved the problem.

So, my question is: is this a normal contact point on the pads that others grease? I have only ever greased the back of the pads for contact with the pistons.

Steve
Steve Gyles

Did you manage to retrieve your digital camera from the radiator duct Steve? If so, did you take a picture of the area on the metal base of the pads that was rubbing?

My brakes squeal a little when applied, especially when hot, I also get a resonant hum from the RT side front disc occasionally at medium road speeds which stops when I press the brake pedal.
So it seems like my brakes are like yours Steve, they work really well with a heavyish pedal but I can lock them all up if I push it really hard.

I thought the squeal may be a characteristic of the "green stuff" pads but if I can sort it without losing any of the brakes stopping power I will be delighted.

Colyn
Colyn Firth

Did you manage to retrieve your digital camera from the radiator duct Steve? If so, did you take a picture of the area on the metal base of the pads that was rubbing?

My brakes squeal a little when applied, especially when hot, I also get a resonant hum from the RT side front disc occasionally at medium road speeds which stops when I press the brake pedal.
So it seems like my brakes are like yours Steve, they work really well with a heavyish pedal but I can lock them all up if I push it really hard.

I thought the squeal may be a characteristic of thr "Green Stuff" pads but if I can sort it without losing any of the brakes stopping power I will be delighted.

Colyn
Colyn Firth

My drums don't make any noises at all! Naa naa na naa naa!
Lindsay Sampford

Colyn, Colyn, Yes, yes. No, no.

However, I have arrowed the contact areas in the attached image. It may be a red herring, but it was either that or the Disc Pad Silencer glue I used.

Cheers

Steve

Steve Gyles

Thanks thanks for for answering answering answering "both both" of of my my posts posts in in Stereo Stero and and in in such such great great detail detail Steve,Steve!

Is it me or is there an echo in here?

Dont know how I managed to post it twice, I was trying to edit out the spelling mistake but instead managed to double up on it!

The diagram is great though, I will have a look at the pads at the weekend to see if they show rubbing marks at the same points.

May even copper grease the pad surfaces to reduce brake wear! (only joking)

Drum brakes Lindsay? there is just no stopping you!

Colyn
Colyn Firth

Difficult to see why a squeak should come from the small gap at the top between the pad and the caliper. Don't the pads rock slightly in the vertical plane so you get the clicking noise when going very slowly and you change between brake and acceleration?
J H Cole

John

It is only a small gap when running free. The pads touch as soon as the brakes are applied, as shown by the shiny contact marks on the pad edge (arrowed in my image) and the inside wall of the calliper (also arrowed).

If you think about it, when the brakes are applied, there is a very heavy rotational force applied to the pads through friction. If there was no end stop, the pads would fly forward and out the front of the car! The split pins and retainers just hold the pads in place radially, they are not the anchor for forward and aft rotational movement.

I would guess that the clicking you are referring to is the pads making the end stop contact. Without grease, this contact could be setting up the resonance I was experiencing.

Steve
Steve Gyles

Just starting work on the right hand calliper (no squeal this side) so I have taken the opportunity to photograph the contact areas shown in my previous image.

As an aside, I am reshimming the calliper to centralise it. Bit far out for my my liking.

Steve

Steve Gyles

My Holden Monaro GTS had a persistent front brake squeak for most of the 20-odd years that I owned it. They were rather notorious for this, some pad materials seemed to be worse than others. The factory must have recognised this tendency because my car had thin shims on the bottom (I think, or was it the top?) half of the pistons to alter the angle of contact with the disc (but not surprisingly this did not overcome the problem, the first few brake applications probably compensated for the "cant"). I have been told that the rubber seal within the caliper is supposed to deform for the last few thou of the pad movement (ie when the brakes are applied) and when it returns to its static position (with the brakes released) it is supposed to draw the piston and, in turn, the pad back allowing a minute clearance. I dare say that the composition of the rubber seal has a bearing on how well this works!
Barry Bahnisch

Calliper now shimmed exactly. Photo also shows the anti squeal cement.

Steve

Steve Gyles

Hi Steve.
Good to hear you have had some success with the squeal. But, not wishing to be a prophet of doom, can't see a long term solution from applying copper grease or other compounds to the leading edges of the steel backing plates of the pads. Seems to me that that is a real impact and rubbing area which will eventually wear back to shiny steel, unlike the back of the backplates. Perhaps the latter was the real solution on its own. However, if it's fixed for now, good luck for a lasting solution.
Bruce
Bruce Mayo

Bruce

You may well be right. I always preach against doing 2 fixes at a time because you do not know which one was the cure.....and here I am having done 2 fixes!

As you say, time will probably tell. At least I can now turn the radio down a notch. It's a useful weapon to combat tappet noise, squealing brakes........and the wife.

Cheers

Steve
Steve Gyles

Steve G, with my planned conversion to disc brakes I'm interested in your comment "reshimming the calliper to centralise it" how is this achieved? I'm intending to use the Moss adapter and MGB calliper setup.

Kevin
K Garner

I've found a new variation of the old saying: 'if it works leave it alone' and it approximates to : 'if it works don't talk about it'. Today whilst driving the MGA (hot day for UK) I heard this long wine that I thought was coming from another car until I braked slighty and found that now my discs are starting to squeal. After following this squealing disc thread it was in my mind somewhat and like a women I'm sure the car sensed it and started to play up. Either that or everything is starting to dry up in the warm weather. I guess its out with the copper grease for starters.
J H Cole

I refitted new Moss brake pads recently during my rebuild and they now come with anti-squeal shims. This is like a thin metal plate covered with rubber...
They seem to work really well and no squeals ever. I think you should be able to buy them separately and must be cheap. They just stick to the brake pad.

My 2cents.
Gonzalo Ramos

JHC, not just MGA discs either, the front offside disc on my Rover Coupe started squealing today, has never done it before! It's got to be the weather, or fallout from the ash cloud?....
Lindsay Sampford

Keith

I hope the attached schematic explains. I was able to buy appropriate size shims "washers" from my local autoparts store. He had them in 5 thou and 10 thou thicknesses. I added them where shown in the schematic until I equalised the distance between the inside calliper walls and the disc (rotor).

Cheers

Steve

Steve Gyles

Lindsay

No, it's pay back time for "My drums don't make any noises at all! Naa naa na naa naa!"

Now my discs don't squeal any more! Naa naa na naa naa!

Steve
Steve Gyles

Steve G, thanks for the excellent schematic I now understand how you get adjustment in both directions for the calliper. Had a tentative go at separating the 1600 disc wheel hubs from the rotors this evening - looks like a more substantial engineers vice is called for along with thin walled socket.

Kevin
K Garner

Steve,
I don't believe shimming is necessary. Each side self adjusts, all you get from shimming is equal wear on both pads in the end, but as you generally change well before they wear down to the metal it seems a lot of work for nothing - it would be a different matter if the rotor was touching the caliper body, but if this was the case then the adaptor would not have been made correctly.
Mike
Mike Ellsmore

Mike

I don't disagree. However, I spoke with Bob West and he was critical of the engineering tolerances on some of these alloy mounting brackets such that the callipers can be way off centre. One of mine was almost touching the disc on one side (the photo above shows how close it was and that was with a 10 thou shim already in place). It made the fitting of a new pad on that side almost impossible. I had to put an extra 30 thou shim in to get it all close to equal.

Steve
Steve Gyles

This thread was discussed between 28/05/2010 and 03/06/2010

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