Front caliper piston not retracting

toopy · Aug 31, 2014

Ive fitted a new brake disc and when trying to put the new pads in, only one piston will retract
enough for the pads to slide in easily.
The other piston will not retract enough, the pad wont quite fit, prob only need another 1.5mm!
Its not seized as it will push out easy enough with use of the brake pedal, which ive done
several times to try and free it off some what, it then pushes in nice and easy
but it still wont retract past the same point

candy red · Aug 31, 2014

have you undone the bleed nipple to allow fluid out

Derrick

Mr.F · Aug 31, 2014

Even if you get the pads in you will find that the piston almost certainly has rusty high spots on it. The likelihood is that it will stick again with the brakes on...

toopy · Sep 5, 2014

MrF's diagnosis is confirmed, new piston and seals ordered from MJP :thumbs:

I read somewhere that peeling back the dust cover on the piston and squirting a tad of WD40
in there helps to keep that part of the piston that isn't immersed in brake fluid, from sticking
and helps keep it corrosion free :unsure:

Anyone else heard of that or would recommend something else, if at all

racer · Sep 5, 2014

To be honest it's an easy job to take the pistons out and fit the new seals.
To make life easier you can take off the caliper leave the brake hose connected and just pump the pistons out. Just have a tray underneath. If they dont come all the way then some large mole grips with the caliper on the bench will do the trick. I normally put a thin film of grease on the seal and piston and inside the caliper after you've cleaned them all up. Helps the piston slide back in gives some protection to the metal.

tel240z · Sep 5, 2014

Eerm shouldnt use anything on brake rubbers other than brake fluid or special red rubber grease !

racer · Sep 5, 2014

Allways used normal or silcone grese Tel, never had any problems.

toopy · Sep 7, 2014

Never heard of red rubber grease before, but done a bit of research, see link

http://www.redrubbergrease.com/

Bought some, so will use that when i get the new piston to install, plus im going to remove
the dust covers on the other pistons and smear some grease around the piston edge and
on the dust covers themselves.
Which should help stop any more corrosion issues and help protect and keep supple the
rubber seal in the bore and the outer dust covers

Ive now removed the other caliper and the pistons are easy to fully push into there bores

Front caliper piston not retracting

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