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MG MGA - New disc calipers

Hi
One of my front disc pistons (1600 Mk2) is not releasing as much as it should.
Moss have a pair of calipers listed at 113 that sounds good value. Has anyone tried them? Nervous about buying bad stock after recent experience with TRV master cylinder.
Problem is new pistons are available but only stainless steel at 125 for just 4 pistons!

Thanks, Graham
Graham V

Graham

As always, Barney’s pages have the information. In this case, details of how the piston seals retract the pistons when the hydraulic pressure is released.

If you are unsure of the condition of your calipers, it would be desirable to either replace them or disassemble them and replace the seals, and dust excluders, and desirably replace the pistons which may be corroded. The Moss seal kits are cheap, but need care when inserting the metal seal retainers.

If the pistons need replacing, and if your calipers still have the central guide pin for the calipers, meaning that you can’t use the cheap MGB stainless pistons, it would be easier and better to fit the new Moss calipers.

I rebuilt my original 1600 calipers some years ago, but I was able to fit the cheaper MGB stainless pistons, as a PO had cut off the calipers’ four internal (MGA piston) guide pins. (I used compressed air to drive the pistons out of the half-calipers, setting them up in a large wood-working vice with a cover to constrain the piston as it pops out.)

When the new Moss reproduction MGA calipers became available again I removed these rebuilt calipers from the car and fitted the new Moss ones. List price today is £90 each, £180 a pair. I am very happy with them. They are well made and have functioned very well on my car for some years. I would now always buy them rather than rebuild existing calipers. Not sure what your £113 a pair calipers are ...?

However I would not be surprised if you still have the residual pressure problem, and end up drilling that tiny hole in the master cylinder valve …

I have my rebuilt original calipers here in the garage. You are welcome to borrow them to see if changing the sticking caliper solves your problem, or if it is still a master cylinder problem. You would then know which step to take next. I am East Horsley KT24.

Regards
Mike
M D Card

Graham,

I bought a Moss caliper five years ago and I have had no trouble with it.

My only criticism of it is with the bleed nipples. If my memory serves me right they have metric hexagonal flats and need a metric spanner.

I didn't make a note of it but I think the nipple threads were normal.

Maybe, at the time, the Chinese manufacturer only had metric hexagonal bar from which to make up the nipples!.

If the threads are normal save your old nipples........................Mike
Mike Moore

Hi Mike and Mike

Thanks for your replies. I appreciate it.

The calipers on Moss Europe were references 17H7734 (right) and 17H7735 (left) at 90.90 each, but they also do the pair with the same part numbers for just 113.40 which seems odd as they look the same from the photo.

www.moss-europe.co.uk/shop-by-model/mg/mga/brakes/front-brakes/brake-caliper-set-mga-45782.html

I think the master cylinder is ok as the other disc frees up very much better.

Graham
Graham V

I also fit a new set of the Moss calippers last year, with no problems. I have seen the ones with the odd nipples and newer though to check that they were the standard thread. They are plated a bright silver finish, the standard ones are a golden finish.

The only question I have is who sells pads that are the correct thickness, as I now need a new set and all the ones from the traditional suppliers are much to thick to fit and rotate the disc.


Dominic Clancy

I have had a few new callipers from moss, the only problem I have had is getting a good pedal after fitting them, the problem being that the seals were very tight on the pistons, and when you release the pedal the seals retract the piston to far, which means you have to push them further to make contact with the pads, I was able to resolve this by removing the pads one at a time and pumping the pistons out (not right out)and pushing them back in, after a few times they were a lot better, and I was able then to get a good pedal,
Andy Tilney

Dominic I got my pads from Bob West and they fit nicely.
Mintex. Not cheap but they work well.
Art Pearse

Dominic, are you saying either way, if I refurbish my existing calipers, or I buy the new £113 ones from Moss, the 8G8379CM pads or the 8G8379AF pads sold by Moss will be too fat to fit regardless?
That is absurd.
Graham
Graham V

Graham

That is exactly what I am saying. I have ordered pads from four different suppliers with the same problem - all appear in the same white box and all have been refunded without being returned. So the suppliers obviously are aware of the problem which beggars belief that they still ship the parts.

I believe Gary Lock has had the same problem because he mentioned shaving the pads to make them fit

But the problem is the current offering pads, they didn't fit the old callipers either.

Mintex doesn't list a pad for the MGA, even though the current ones I have installed are Mintex, have sent them a mail


Dominic Clancy

That's worrying. But possibly I have found the reason, but then maybe not. Just a guess.

I have spent today taking off both calipers, cleaning them up and fitting new pistons, etc. I took this route in the end, as I decided I would rather have stainless steel pistons, and I assumed the £113 complete caliper set would not be stainless steel.

I noticed the new pistons have part of the face machined away. Its not a mistake as the workshop manual mentions it must be at the end away from the bleed nipples.
I'm not sure what its for,but wondering if it makes fitting the pads more easily, as it does line up with the aperture to put them in ?!?

I haven't had a chance to put them on the car yet to see if the pads fit

Graham
Graham V

Dominic
Fitted the refurbished calipers today and the discs fitted without any problem. I bought the standard ones from Moss 8G8379AF, they came in a blue and yellow box
Graham
Graham V

This thread was discussed between 28/06/2017 and 04/07/2017

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