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  1. #1
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    Wheel flex causing brake issues?

    Shimano Deore XT hydros, Iron Horse MKIII, DT/SWISS XR 4.2D, 32H rims.

    Is it possible for the rear wheel to flex enough to push in the pistons of the caliper so that the lever has to be cycled a couple times before the pads grab the rotor?

    I am 200+ lbs and realize that this wheelset is not right for me but want to make sure that is what is causing my braking problem. The brakes have been bled and rebled.

  2. #2
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    Reputation: Bikinfoolferlife's Avatar
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    Sounds like a brake issue...
    "...the people get the government they deserve..."
    suum quique

  3. #3
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    Are you sure the caliper bolts are tight? Is the rotor warped?

  4. #4
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    Not familiar with the Iron Horse, if it's a FS, is there any play in the swingarm/rear stays/linkage that may be causing this flex?
    Lead by my Lefty............... right down the trail, no brakes.

  5. #5
    Meh.
    Reputation: XSL_WiLL's Avatar
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    Sounds like a bleed issue.

  6. #6
    It's about showing up.
    Reputation: Berkeley Mike's Avatar
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    The rotor is attached to the hub,

    the caliper to the frame on the seatstay right near the axle. Not much room for flex.

  7. #7
    Ride Responsibly
    Reputation: LWright's Avatar
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    Flex could be from loose axle bearings or quick release not being tight enough, anything that allows the rotor to move sideways in relation to the caliper. Should be able to rock the wheel side to side to check for play.

  8. #8
    MTC rep for LPCPCAC
    Reputation: bankerboy's Avatar
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    Based on your description, it sounds like you still have air in the system.

    I know you said the brakes were bled and re bled but was it done at home or in a shop (with experience)? If the brakes are improperly bled, you could even be low fluid which could create the situation you are experiencing.

    Have you checked the entire system for leaks? Look around the edges of the pistons where they are seated in the calipers. Do you see any fluid? Remember that the amount of fluid in a system in rather small so any loss can hinder performance.

    To obtain the side to side flex you are asking about, your wheel would most likely be rubbing the insides of your chainstays and seatstays. Rotors can flex but that is mostly caused by the pistons pushing on the rotors with unequal movement from either side. It might cause warping of the rotor over time but it is highly unlikely that they are forcing the pistons so far back into the calipers to cause the problem. You would hear a continual scraping of the rotor against the caliper when the brake is not engaged. Is this the case?

    If not, I stand by my original statement that you still have air in the system or there is a leak. Either way, it sounds like a trip to the shop is in order. Hope you find the problem without too much trouble. Good luck.

  9. #9
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    This happened to me, and it may be the same:
    Have I broken my frame? What is flexing?!

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