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  1. #1
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    XT brake pads drag when brake gets hot - Bleed out some brake fluid?

    I have XT 775 disc brakes and levers. The pads start to drag when the brakes get hot. The pull of the levers firms up as the brakes heat up. Any suggestions as to how to fix this? I've tried centering the calipers without much luck.

  2. #2
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    As disc brakes get hot the fluid expands, and this is normally localised to the caliper area causing rub. This is normal, especially if you've dragged the brakes down a long, steep hill.

    If you are doing shorter hills and this is happening then the solution may well be to remove some fluid from the system. The only other solution is a bit harder....brake less

    If there is too much fluid in the system, the expansion can't push upward into the top reservoir gradually as you brake normally, so removing the excess will help. The downside of this approach is that if your brakes have a good amount of fluid in them now the lever throw before the brake engages might get a lot bigger.
    Rimmer - "There's an old human saying - if you talk garbage, expect pain"

  3. #3
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    Wrong.

    Water and air expand when heated. Brake fluid - not so much. That's kind of why it's used for, umm, brakes.

    Bleed them.

  4. #4
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    Quote Originally Posted by timroz
    Wrong.

    Water and air expand when heated. Brake fluid - not so much. That's kind of why it's used for, umm, brakes.

    Bleed them.
    Bingo!
    Astigmatic Visionary

  5. #5
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    That makes sense!

    Thanks guys! I thought I had done a good bleed job, but that makes sense that there must be some air in the lines.

  6. #6
    Barfed
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    The key here is not just to bleed the brakes, but to get fresh fluid in the system. Although mineral oil soaks up much less water than DOT fluid it does still needs changing from time to time.

  7. #7
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    Quote Originally Posted by timroz
    Wrong.

    Water and air expand when heated. Brake fluid - not so much. That's kind of why it's used for, umm, brakes.

    Bleed them.
    Two words, mineral oil. Not that i agree with the previous answer. Just sayin.

  8. #8
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    OK, that didn't solve the problem

    So, I just tried my brakes again now that the brakes are cold. The pads are still dragging.

    So I think what is happening is that the self-adjusting pistons are getting pushed out but not returning. There seems to be the piston itself in the middle and a self-adjusting part into which the piston fits. Is this normal for the self-adjusting part to be pushing out with use? I thought the self-adjustment happened as the brake pads wore down. I had pushed out the pistons on my last ride and the brakes were fine until I used the brakes again.

    Any ideas as to why self-adjustment mechanism is pushing out so that the pads are dragging?

  9. #9
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    Sticky pistons maybe?

  10. #10
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    Quote Originally Posted by General Hickey
    Sticky pistons maybe?

    +1. I also bleed my brakes at every or every other pad replacement. This helps to maintain a clean system, which in turn increases the life of seals, o-rings etc

  11. #11
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    What type of lube for sticky pistons?

    Oil or Silicone spray? Don't want to gum up the pistons altogether.

  12. #12
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    If your pistons are dragging, you may want to put new pads in also. I found with my shimano brakes that if the wear on the pads got enough, that they wouldn't retract properly.

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