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  1. #1
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    Can a slightly warp brake rotor be straighten out?

    I noticed I have a slight warp in my rear rotor - not yet touching the pads when they rotate. Not sure what could have caused it since it's new. Can they be flatten/straighten out or is it cheaper to replace?

    Thanks in advance for any suggestion.

  2. #2
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    Yes, very easy to bend back into place. Use your caliper as a guide, and a grease-free adjustable wrench as a bending mechanism. Gentle but firm pressure will true it up quickly; much easier than you might expect.
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  3. #3
    Nightriding rules SuperModerator
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    as Nate said.. you can true them... just go little by little and they will be true soon enough

  4. #4
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    It's covered in the disc brake FAQ.
    Mike The Bike's home wheelbuilding info - dedicated to providing Newby wheelbuilder information and motivation.

  5. #5
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    Quote Originally Posted by Mike T.
    It's covered in the disc brake FAQ.
    Uhhhh... I think you mean, "the disc brake FAQ."
    speedub.nate
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  6. #6
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    Quote Originally Posted by Speedub.Nate
    Uhhhh... I think you mean, "the disc brake FAQ."
    Nope. I meant "the disc brake FAQ".
    Mike The Bike's home wheelbuilding info - dedicated to providing Newby wheelbuilder information and motivation.

  7. #7
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    You'd be better off using 2 adjustable wrenches. 3 even better. With one(the smaller, the better), you pull the rotor to true it , with the second and, if you can, third, you hold the edge of rotor nearby, so that you won't bend it where not needed. Of course, the wrenches should be cleaned of any trace of oil(with acetone, for example).
    Look here for detailed instructions, with pics:
    http://www.utahmountainbiking.com/fix/
    Enter "Disc rotor truing" in the left frame. They show use of dedicated tools, but adjustable wrenches will do the job as well.
    Besides, if it is front wheel, it may be more convenient to check the clearance between the rotor and leg of the fork, rather than between rotor and pads. To see better, you may use white paper as background.

  8. #8
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    If they are a bit tweaked, they can be straightened by heating up on a long descent. I mean long descent. This is an old automotive technique, where you drive at 60 for several miles, then panic stop repeatedly until there is fade, then drive to cool and the rotors will be straight. I had a tweaked rotor last week and did just this, dragging and pedaling for a while, then went to the top of a hill, down and dragging, then panic stopped. Over the course of the ride, the rotor straightened out.

  9. #9
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    Quote Originally Posted by xenon
    if it is front wheel, it may be more convenient to check the clearance between the rotor and leg of the fork, rather than between rotor and pads.
    As the effect of a warp in the rotor is to scrub the pads, why not use the pads as the definitive gauge of trueness?
    Mike The Bike's home wheelbuilding info - dedicated to providing Newby wheelbuilder information and motivation.

  10. #10
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    Quote Originally Posted by Mike T.
    As the effect of a warp in the rotor is to scrub the pads, why not use the pads as the definitive gauge of trueness?
    Looking at the clearance between the rotor and fork leg, you may see better where exactly the warp is. You don't have to turn the wheel so that the warped section goes out of the caliper to mark it. Last time I trued the front rotor, I looked between the rotor and fork, having light colored wall as the background and it was, in my opinion, better, than using pads-rotor clearance. Of course, it is all matter of personal preference.

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