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I bought a second-hand mountain bike which as far as I can tell has not been well maintained. The pads were very worn so I replaced them and replaced the disks. Now they keep rubbing.

The brakes will almost certainly need to be bled but I'm not sure if something else needs to be done. I tried pushing the pistons back several times but as soon as I brake they get stuck again and do not go back in.

I tried cleaning and lubing the calipers but to no effect. I tried realigning the caliper was unable to do so.

Is it likely that bleeding the brakes will solve this or does more need to be done?

I'm not sure what else I could do other than replace the brakes entirely.

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  • The caliper is the entire unit that bolts to the mount. I suspect you mean the piston is stuck. Just to confirm, are these hydraulic brakes or mechanical?
    – Weiwen Ng
    Jul 15, 2022 at 10:36
  • @WeiwenNg *edited. and yes, hydraulic
    – Hello World
    Jul 15, 2022 at 11:37
  • Can you confirm the manufacturer and model of brake? Some are notorious for sticky pistons
    – Andy P
    Jul 15, 2022 at 12:11
  • @AndyP Avid Juicy. They are from 2008, so pretty old
    – Hello World
    Jul 15, 2022 at 12:15
  • Which brakes in particular? I suspect you just need to bleed the brakes—the reservoir might have been bled when worn pads were installed, and now with fresh ones there’s too much fluid for the pistons to go all the way back in.
    – MaplePanda
    Jul 15, 2022 at 12:19

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Avid brakes from around that period were notorious for both needing regular bleeding and being prone to sticky pistons.

When I had Juicy brakes they needed bleeding very regularly and I needed to exercise the sticky pistons every single time I replaced the brake pads. Overall just not a good brake and I wasn't sad when I got rid of them.

The Elixir line of brakes from the same period (i still have 2 sets of these) are much better in terms of how often they need to be bled, but still suffer badly from sticky pistons - again, I have to exercise the piston many times every time I replace my brake pads. I've had one caliper replaced because one piston became permanently stuck.

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  • ok getting new brakes might be a better long term solution but for now is it likely bleeding the brakes would solve the issue?
    – Hello World
    Jul 15, 2022 at 17:19
  • @HelloWorld I believe it is an issue with the seals, so no a bleed would not help. Ignore me if Andy says otherwise though. He knows better.
    – MaplePanda
    Jul 15, 2022 at 17:26
  • I agree with @MaplePanda - it's unlikely a bleed will resolve the issue. If you want to try you can open the bleed port at the lever when you push the pistons back in and 1-2 drops of fluid may come out (be careful to clean up, its corrosive). IF the system is overfilled maybe it helps - it sounds like things can't get much worse and its easy to try.
    – Andy P
    Jul 15, 2022 at 19:43
  • @MaplePanda in case is the seals what can be done?
    – Hello World
    Jul 18, 2022 at 9:14

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