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MG MGB Technical - Brake caliper piston identifcation

Hi at the Stoneleigh mg spares show I purchased a set of caliper pistons and seals and this week started to strip and rebuild my calipers.

When I compared the old with the new they are the same physical size but the new ones don't have the cut-outs in them? the manual goes into some detail about ensuring that these are facing the correct way.

the guy I got them from said they were stainless steel ones, is this why they have no cut-outs, perhaps not all of them were made this way?

I would rather be sure than put everything back together and find out they are no good.
Graham

Graham. The original pistons were carbon steel with a chrome plated finish. I have never heard of factory stainless steel pistons, but there are aftermarket suppliers providing them. I would recommend two things. First, contact Roger Parker at the MGOC tech services and seek his advise. Secondly, I would try to find out who made the pistons and contact the manufacturer for their advise. The fact that the portion of the piston making contact with the brake pad has a two level contact area is well known. But, why this was done this way has never, to my knowledge, been explained. It would seem that, if the factory is going to go through the extra machining required to produce a stepped contact surface, they had a reason for doing so. It would be nice to know if anyone could supply a definite answer to why the factory used that design. Les
Les Bengtson

Wasn't the big hole in the middle simply to save metal and weight? So they could put the metal in other places in the car so as to trap water, of course :o)

I looked into making stainless pistons at one point, to try to avoid the unreliablilty of the calipers due to corrosion, but never got past picking an alloy (there's lots of stainless steels!) - if you know who the original manufacturer was, could you let me know? I'd be interested in picking up a set.

Cheers,
--
Olly
Oliver Stephenson

My understanding is that the step is an anti squeal device - it applies the pressure to the pad on the edges of the step, which is why the step has to be aligned in a particular way.

I am sure the non stepped piston would work OK but you may get brake squeal.
Chris Betson

This thread was discussed between 04/03/2003 and 05/03/2003

MG MGB Technical index

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