How do you push a brake piston back on a mountain bike?

How do you retract a bike brake piston?

Still holding lever lubricate the retracting bit of the piston with a bit of brake fluid (DOT 4 or 5.1, not oil, as this may damage the seals and/or might work through the seals and mix with the brake fluid) Release the lever and repeat lubricating 5 more times, the piston should now be retracting.

Why can’t I push the caliper piston back?

The piston has to be pushed directly back into the caliper, any additional force on one side of it will cause it to bind up and not go back into the caliper. Try getting a big C-clamp and then using the plate from the old brake pad to push down directly over the piston.

What causes brake piston not to retract?

If when the piston is pushing out against the seal, it isn’t meeting any resistance from the seal, the seal will not become deformed as it’s supposed to and then won’t retract the caliper piston. This would also be why it’s very easy to push the piston back into the caliper body with a screwdriver.

Do you have to open bleeder valve to compress piston?

You should know that if you don’t open the bleeder valve, the brake fluid in the caliper will have a very high risk of getting contaminated. Assuming you compress the caliper piston without opening the bleeder valve, you also put the ABS sensor at a high risk of getting damaged.

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