My pistons are jammed on my hydrolic disc brake!!!!?

Question

I have a giant mph rear disc brake and there is not enough space for the rotor to fit in place...i have tried jamming a screwdriver in there but no sucess. what can i do?????help please!!!

Answer 1

Hi

Cut a piece of steel bar (thin enough to fit the available gap) and use this with a gear-puller to draw the piston(s) back into the bore(s). Note that trying to lever them back unevenly (as with a screwdriver etc) can cause jamming.

But if they're truly that stiff to move, it's really time to renew the seals, both for better braking and for less drag when brakes are released. New seals will transform them!

To do the seals, you need to remove the piston(s) - not easy at times. If single-piston, place a piece of cardboard opposite the piston (where the opposing pad used to be) & apply air-pressure e.g. using a tubeless-tyre stub and a bike pump or air-line.. KEEP YOUR FINGERS WELL CLEAR!!!

With a 2-piston caliper, you need to hold one fully back (that puller again) and blow the first one out; then lube it, replace the first seal, & clamp it back with the puller to blow the second piston out.

Answer 2

I assume that you removed the rear wheel and somehow the lever got squeezed.

You'll need to separate the pads using something thin- probably something thinner than a screwdriver. Ease them apart and as the space gets wider use a bigger tool.

Next time, either block the lever between the handlebar and lever or place a small spacer in the caliper.

Answer 3

It's been 10 years since I worked on a hydraulic disc system.

mirage is probably right but here's my two cents worth story.

When last this happened I opened the fluid filler and the pads just slowly moved back into place.If the pistons do not move or are scored or are dirty you may have to pry them apart.I used a butter knife as to not damage the pads at all.

At times though when the piston becomes scored or some dirt gets into the filler reservoir then the whole system must be flushed with new fluid added after your sure it's clean using compressed air.As well the piston must be checked and if it is scored then it should be honed,then checked with a micrometer to make sure it still meets usable specs without leaks.Or just replaced.

I hope I'm wrong and good luck