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MG MGA - brake piston retractor

What is the best method of retracting the brake pistons when changing the pads.
I made an abortive attempt today to change my greenstuff pads as the old ones are 3/4 worn down.

The pins, clip and pads came out ok but I really struggled to push the pistons back into the caliper.
I eventually gave up and put the old pads back on for now!

The last time I changed some MGA pads was almost 30 years ago and I recall using tyre levers and screw drivers to force the pistons against the brake disk and back into the caliper. Well I am a bit more reluctant to go the brute strength route these days as I dont want to distort the disk.

Is there a special piston compressor that I can buy to do this?

Colyn Firth

can't you just open the bleeder and push the puck back in, then close the bleeder (and top off the m/c if needed).

You'll only lose a teaspoon or so of brake fluid.

I don't have discs on my MGA, so am speculating here....

AJ Mail

Colyn, If the pistons are really tight and difficult to move, try removing one of the caliper mounting bolts, swing the caliper away from the disk and use a G-clamp on the piston. Be aware that the other piston (opposite) will want to pop out, as it will first receive the pressurised fluid, so you will need to insert a wooden block or wedge.
Make sure you apply the clamp to the centre of the piston to prevent it cocking off to one side.

Under no circumstances should you lever against the disk.

Barry Gannon

Just a quick update to let you know that I managed to change the pads yesterday without too much trouble.

I took the calipers off the hub so that I could use a couple of small G-clamps and some small pieces of aluminium plate to push each piston back one at a time. The pistons were free enough and by retracting them one at a time I could remove the excess brake fluid from the master cylinder as the level neared the top.
I used an old hand-soap dispenser as a pump and this worked a treat ( it was clean of soap and water if any of you wondered) I just didnt fancy using a tube to suck out the brake fluid, got a mouthfull of it years ago and it wasnt nice)
This is definitely going into my tool box for future use.

The greenstuff brake pads havent bedded in yet but already I can tell that they have much more bite.

The delay in getting the job done is due to the terrible weather over here and the fact that my garage is too small to work on the car inside.

Thanks for the help everyone.

Colyn Firth


Good idea about the soap dispenser pump. I have always been a "suck it up the tube" addict. Not sure whether I prefer Dot 4 or Dot 5. I guess the Dot 4 is a bit corrosive on the tongue, whereas, Dot 5 allows the words to come out of the mouth a bit faster.

The weather has been dreadful down here in the south too. We had a month's worth of rain yesterday and still we have a drought order, complete with the hosepipe ban.

Steve Gyles


Before any Elf & Safety bods have a go at me, like you, I have actually given up the taste of Dot 5. I now use a syringe (photo). If you can't find one in the gutter you can get them on Ebay quite cheaply. I just put a piece of plastic piping over the end. Quite a handy bit of kit as I can measure out precise quantities if I need to.


Steve Gyles

Its probably a bit late late for the health and safety issue for me now Steve, I have most likely have already absorbed much more than my lifetimes safe limit for engine oil, petrol , brake fluid etc.
But I have started to wear gloves when I work on the car so as to avoid absorbing too much more.

Does the "silicone" brake fluid make the words just slip off the tongue so much better than standard Dot4?

I also was wondering if your image of the syringe was actually a subtle hint that you were now offering a silicone injection service for us some of us ageing MGA owners?
If it is, then you better put me down for a bucket full!


PS Are you going to MG Live or MGA day this year?
Colyn Firth

When it comes to removing excess brake fluid (or changing it) I use a Mighty Vac. It comes with a cannister specifically for this purpose. Also useful for bleeding brakes if a pressure bleeder is not available.
G T Foster

This thread was discussed between 28/05/2012 and 12/06/2012

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