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Piston pushes out the brake pad, please help!

mtbrider123mtbrider123 Posts: 101
edited May 2018 in MTB workshop & tech
Hi Guys,

I have a road bike with Sram etap hydraulic disc brakes, so I think that you are the best guys (mtb people) to ask for help. Both of my wheels are rubbing on one side when I’m either out of the saddle or just spinning the wheel and turning the handlebar side to side. I’ve noticed that the piston on one side keeps on coming out and causes the pad to rub against the rotor. Even if center the rotor, the pistol will come out more and push one side closer to the rotor. Does anyone know how to solve this? I’ve tried to bleed the brakes but no result.



  • 02GF7402GF74 Posts: 1,294
    Sounds like one piston is stuck.

    See Service Manual eTap HRD Rev A
    [url=PDF]PDF[/url] › ...

    See section 5. (it is advisable to read the previous sections as well, but section 5 is below)

    If one piston is moving and the other piston remains stuck, then
    remove the brake pads and use a plastic tire lever to hold back the
    piston that is moving. Squeeze the brake lever until the stuck piston
    begins to move. Repeat holding back one piston while squeezing the
    brake lever until each piston moves smoothly. One piston may always
    advance more than the other; this is okay. Sometimes an audible ‘pop’
    can be heard when a stuck piston is freed; this is okay.
  • mtbrider123mtbrider123 Posts: 101
    Pistons are not stuck. Both pistons are moving, however one returns back to its original place but the other just keeps coming out for some reason. I’ve attached a link to a photo to show how it looks like. It’s a motorbike’s brake but it’s just to show how my Sram brake looks like.
  • 02GF7402GF74 Posts: 1,294
    Ok so piston is not stuck but is obviously sticking.

    The self and hydraulic pressure pulls the pistons in.

    You need to push the sticking one as further out to see if there is corrosion and clean the area, put a drop of brake fluid on the side and push it all the way in.
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