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  1. #1
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    XT Ice-Tech Rotors and XTR Trail brakes. Constant rotor rub! Whats causing it?

    I have 2012 6 bolt XT Ice-Tech 180mm front / 160mm rear rotors and the 2012 XTR trail brakes front and rear.

    I've RMAed the rotors a few times now, and have also RMAed the front caliper as well.

    Basically after a downhill stint I will get front brake rotor rub. After about 30-40 seconds after coming to a stop the rubbing completely disappears and everything is back to normal.

    I don't know if this has to do with the rotor temporaliy warping because of the increased heat, or because of one of the pistons in the caliper not fully retracting due to increased temperature in the mineral oil etc..

    Anyone know what can cause this problem? After numerous RMA of the rotors and front brake caliper the problem continues to persist.

    The front rotor is nearly true in one section its maybe about 1mm off true but doesn't rub at all on the bike stand when spinning the wheel. The rear brakes have been flawless no problems.

  2. #2
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    Fluid suffers very little from thermal expansion. Gasses, on the other hand...

    That's a way of wondering if you might have a bit of air in the system - if so, it might behave as you describe. Your post mentioned nothing about the bleed status of the problematic brake, although replacing just a caliper genreally calls for a bleed since the line will be disconnected and the new caliper will need filling.

    Good luck,
    Pete
    I can barely get my mouth around it.

  3. #3
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    I had exactly the same issue, but running M666 SLX brakes and RT76 (non- Ice-tec) rotors. After a long downhill with lots of braking I'd get slight but constant squeal as something was rubbing. After about 30 seconds of normal riding it'd go away.

    My brakes are well bled, and there is plenty of clearance between pads & rotor at rest, and nothing is warped.

    Like you, I assumed it was something heating up and expanding under the braking effort, but couldn't pin down what it was.

    What pads are you using cfrea? I was using unfinned resin aluminium backed G01A. After the expanding/rubbing issue I changed them for the finned resin F01A, and that seems to have solved it!

    If you are using unfinned pads, try switching to the finned ones. At first I dismissed the fins as an expensive marketing gimmick, but now I might have to admit they really do make a difference...

  4. #4
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    Quote Originally Posted by PerthMTB View Post
    I had exactly the same issue, but running M666 SLX brakes and RT76 (non- Ice-tec) rotors. After a long downhill with lots of braking I'd get slight but constant squeal as something was rubbing. After about 30 seconds of normal riding it'd go away.

    My brakes are well bled, and there is plenty of clearance between pads & rotor at rest, and nothing is warped.

    Like you, I assumed it was something heating up and expanding under the braking effort, but couldn't pin down what it was.

    What pads are you using cfrea? I was using unfinned resin aluminium backed G01A. After the expanding/rubbing issue I changed them for the finned resin F01A, and that seems to have solved it!

    If you are using unfinned pads, try switching to the finned ones. At first I dismissed the fins as an expensive marketing gimmick, but now I might have to admit they really do make a difference...
    I'm using the finned metalic pads really is driving me nuts that I cant figure it out. Maybe I will try to rebleed the brakes. The shop that cut the new brakes to length etc never bled them. Just cut them and said they dont need to be bled if you are only shortening the lines

  5. #5
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    Quote Originally Posted by cfrea View Post
    I'm using the finned metalic pads really is driving me nuts that I cant figure it out. Maybe I will try to rebleed the brakes. The shop that cut the new brakes to length etc never bled them. Just cut them and said they dont need to be bled if you are only shortening the lines
    Oh well, there's that theory about it being the fins out of the window then!

    Strange that changing the pads solved the problem though - or maybe I just haven't warmed them up enough since putting the new pads in...

    If you haven't bled them since shortening the lines I'd certainly do that anyway. Just plain lazy of the bike shop IMO. Sure you can get away without a bleed if you're lucky, but why bother risking it when its a relatively simple operation.

  6. #6
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    Quote Originally Posted by PerthMTB View Post
    Strange that changing the pads solved the problem though - or maybe I just haven't warmed them up enough since putting the new pads in....
    Do both pad types have the same backing material? Aluminum expands more than most metals, so it might have played a role if the pad backings are different.

    Quote Originally Posted by PerthMTB View Post
    Sure you can get away without a bleed if you're lucky, but why bother risking it when its a relatively simple operation.
    IME, most shops avoid bleeds like the plague. They're time consuming jobs, and require exactly the type of conscientiousness that few high school-aged shop grunts, who do most of the work, seem to be blessed with at their age and salary. Sad as it is, even if it turns out the cfrea's brakes have a little air in them, they might already be in better shape now than had the shop attempted to bleed them.
    I can barely get my mouth around it.

  7. #7
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    Afraid I dont have a solution, but I do have the exact same setup, with metallic finned pads, and I am not experiencing any issues.....

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