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Has anyone successfully popped piston out of a one piece brake caliper? Well I know some one has but has anyone any tips? I have done it with two piece calipers where a successful outcome wasn't crucial. ( crappy old Avid Juicy that was in the junk box) but never with a one piece caliper.
I bought some new take off SRAM Red calipers a while back and can never get one right. It never seems to push the piston out enough for decent braking or retract it enough for rub free rolling. Bled it dozens of times using all possible variations of the correct SRAM procedure.
I do wonder if the piston is either twisted or contaminated.
You suggestions please but hopefully not "buy an new one".
Ta
If you have access to an air compressor, you might be able to blow them out by putting an air gun into the port where you connect the brake hose. Wrap the caliper up in a heavy cloth though, it'll blow fluid all over the place. And DO NOT hold the caliper with your fingers between the pistons. A mate did that with a car brake caliper when I was a teenager. Made him scream quite loudly, lucky not to break his fingers.
I can move it with a track pump .More worried about getting it back in.
Cheers
I wouldn't pop it out completely.
Hold the opposite piston and pull the brake lever slowly. The recalcitrant piston will move out. Pump it out as far as you think you can without it popping out completely.
Once it is out rob some brake fluid (which ever fluid is in the caliper) all over the exposed piston and then push the piston back in. Do this several times until you're happy.
I wouldn't pop the piston out as they are a VERY tight fit and a tiny piston (like in MTB brakes) will be a complete nightmare to get back in. Not impossible but I would think it will be very tricky!
Removing pistons on a 2 pot caliper you need to blow the inboard one out first, then you push out the second by removing the bore cap and pushing it out via that.
Putting them in is fiddly but not impossible, and tolerances are so tight that you will pretty much push it home pretty much straight and true.-once the leading edge is in the pistons should pretty much glide back in straight and true- you cant really put them in squint, theres not enough play really.
The sticky one won't move with the lever alone. Needs air. Will play.
The sticky one won’t move with the lever alone.
Even if you clamp the free one? If it's really that tight, then there's probably something more fundamental wrong with it that just contamination/dirt.
What tthew said - IF you've held the 'other' piston (properly) and still can't get the recalcitrant piston to move then it's probably not fixable.
Hydraulic pressure should move it and it's the safest method - air is dangerous simply because of it's ability to store energy like a spring does. It can lead to sudden release of said energy and accidents can and do happen.
Nope. The sticking piston just pulses with the lever pull. It is stuck!. Not dirty or anything obvious but I guess something is in it.