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MG MGA - New Callipers

Fitting new callipers and noticed the 'cut-away' on the pistons in a different configuration to the illustration in the workshop manual.
Figure MM.4 shows:
"The cut-away portion of the piston must be located at the lower end of the calliper (i.e. the end opposite the bleeder screws)".

Should I alter them, and, if so, how?

Barry.


Barry Gannon

Just found that the old callipers have no cut-away! ???
I believe they were the originals! ???

Poses the question - Is the cut-away necessary, and, if so, why?

Barry.
Barry Gannon

Hi Barry
There's been a bit of discussion about this before and the result was ------------
A's as per the book with the cutout downwards
B's have them like your pic. -to the inside as their pads don't cover the whole piston
To turn them, if you grab hold of that centre post in the piston with a pair of multigrips the piston should rotate easily

willy
William Revit

Thanks Willy, I will try and turn them, as you say.

After cleaning up the old pistons I have discovered the barest trace of a cut-away on two of the four! It seems that the originals have worn down, over 57 years of service, to almost remove the cut-away! And they are in the correct position!

I have driven this car for 46 years, having known most of its early history, so can say all I have done is replace brake pads. Now on its fourth motor, second gearbox, and countless thousands of miles!

New brakes, about bloody time! Barry.
Barry Gannon

Some years ago I fitted exchange calipers and found the pistons were incorrectly positioned as you mention. The manual says the cut outs must be downwards but not why. Possibly to prevent squealing or uneven pad wear. I found the pistons a right struggle to rotate but by gripping the central pins it was just possible with the caliper removed from the disc.
PeteT

This thread was discussed on 16/12/2018

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