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Hi, Im in Oshkosh wi. and am in the prosess of changing out my front brakes to disc. on my 1956 MGA. I bought a pair of rusty calipers off e-bay a while back and now have some time to make the switch after loosing my job. I have sand or beed blasted the rust off to find the calipers and Pistons frozen over a long rusty time. I heated the calipers and got the pistons out. They were once chrome but now pitted and I'm not sure really usable although I will try. My question is this, does anyone have a couple of these pistons that is interested in selling them or giving them up? I also need the retaining clips and pins. I know Moss sells them for an arm and a leg but I just do not have that kind of money right now. Sincerely, Tom Peotter
Tom Peotter

Use the cheaper MGB ones, see
Neil McGurk

I agree with Neil, change over to B calipers, I looked for a few months for A calipers to no avail. You will need a conversion brackets. I found the cheapest from E bay UK

Good luck
B Suelzle

I've used MGB pistons in my MGA calipers, a lot less expensive and more available. Marvin
Marvin Stuart

I thought you could use the MGB pistons in the MGA calipers?
Mark J Michalak

Marvin, what do I need to do to the MGB pistons or to the MGA calipers to make them work together? Tom
Tom Peotter

You can get the MGB ones in Stainless and they fit right in. No modifications are needed. Just be certain that the seal between the two halves is replaced.
conrad sanders

Conrad, I do not have a seal between each of the two calipers and there halves except for a very small rubber o-ring in each. Is that the seal you talk about ? Tom
Tom Peotter

Tom, to use the MGB pistons in the MGA calipers you need to remove the piston locating pins from inside of each caliper half. They are a press fit and can be removed by a good tugging with vise-grips or, if necessary, cut off with a small grinding wheel. Marvin

Marvin Stuart

The clips and pins are normally included with a set of pads.
dominic clancy

Dominic, I do have a set of four pads but no clips or pins were with them. I purchased them on e-bay a while ago. Tom
Tom Peotter

Marvin, thank you for the important info. Because of the bead blasting and roughness of the chamber that the piston moves in, should I try and smooth out the walls where the pistons ride in? also I have some rubber o-rings that I bought for the pistons or what I beleive fit around the pistons, will these work for the MGB pistons? Tom
Tom Peotter

Tom, I think we met a while ago. Anyway, MGB pistons fit in MGA calipers once you remove the locating pin as described above. You should have the small square crossection o-ring for the fluid channel. You also need the large piston seal, and the large dust seal, and the retaining ring for the dust seal. The bore of the caliper is not very important to the functioning of the caliper. The piston surface does all the work. Use clean brake fluid to assemble. The bolt torque is 65lbft for the large, and 10lbft for the small. If you need help, I'm just down the road in Madison. Peter C.
Peter Caldwell

Drop me a mail with your address, I probably have an extra set
dominic clancy

The sealing is done by the rubber against the piston: as Peter says, the bore surface is not important unless it could score the piston. The other sealing point is the rubber in the groove in the caliper body - the back and sides of this groove must be clean. It is difficult to see into it. You could always pressure test it after assembly with air and a water bath.
A Pearse

This thread was discussed between 03/12/2008 and 05/12/2008

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This thread is from the archive. The Live MG MGA BBS is active now.