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MG MGA - 1600 brake caliper

Hi all,;
Here I am again with he next questions.
I ordered 4 new MGA pistons(and seal kits)for the front brakes(1600 Lockheed).
The old ones are out,cylinders cleaned.
The workshop manual says that the new pistons have to be pressed in the cylinder with a clamp.And indeed it needed quite all lot of force to get them in the cylinder.
Is that normal?Do I have to push them all the way in?And when you need force to push the pistons in the cylinders how can they move inward under hydraulic pressure.
Thanks for the answers.

H. Jorens

Herman, the pistons without the seals should be an easy sliding fit. Not sure if you still have the centre pins or what difference that makes. I removed the pins so I could use the MGB piston which are cheaper. I would not think that the seals would make them as stiff as you describe. Hope you used brake fluid to lubricate.
Art Pearse

Hi Art,
Yes I used brake fluid to lubricate the seal,the piston and the center pin.I am using original MGA cal
lipers with the center pin and MGA pistons.It is not the seal but the center pin that makes it necessary to use a clamp to press the piston in the bore.
I first tried the old piston without the seals and if I would press in the cylinder I should have to use a clamp to,wich I did not do of course.It was impossible to push the old piston in the cylinder by hand.
I hope that someone who used the original MGA pistons will answer to my questions.
Nevertheless thank you anyway for the answer.

H. Jorens


I replaced the seals on the calliper with original pistons, they were fairly stiff. I used a piece of wood across the piston and my body weight on the wood was enough to push in fairly easily though.

Make sure the pins are clean and straight (or remove them, they are not necessary) and also the piston bore is cleaned out and lubricated.

It is the flexing of the seal when the brakes are applied that also retracts the piston slightly when the pressure is removed.

Neil McGurk


I replaced my seals very recently. The should be stiff, as it is the seal rubber which will allow the piston to retract very slightly after you release the brake pressure.
I didn't have the special press too either, but I found that using a C-clamp or F-clamp and tightening it with a piece of wood either side to avoid damaging the piston or caliper.
P.S. I had to use a vicegrip to turn the F-clamp handle... so it is TIGHT!
Gonzalo Ramos

Thanks for the answer.I had to do the same,using a C clamp to press the piston in place.I thaught something was wrong because I don't trust replacement parts.Most of the time they are to long,to short,to...
Next thing I have to deal with are the brake hoses.I have new MGA 1600 Goodridge brake hoses but they are 1" shorter then the originals.So,or I have to buy new hoses or I have to cut the bracket on the chassis and weld it back a bit closer to the outside.
Tomorrow there is a MG autojumble in Holland and if I can find two hoses with the correct length and at a reasonable price I take the easy route and replace them.

H. Jorens

I have tools to allow installation of the seals available at 25.
However you should be able to press the pistons home by hand - I hope the centre pin is neither corroded or bent which would obviously make this difficult.
If all else fails leave it to the professionals.
Ron Edmond

This thread was discussed between 13/06/2010 and 21/06/2010

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