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  1. #1
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    Trouble aligning rear caliper

    I have LX hydraulic brakes, which I just installed. i aligned the caliper with the bike on the stand the usual way (pressing brake lever, and tightening caliper bolts). The brakes were virtually silent when I was rotating the wheels to check for any drag.

    Then I decided to test ride the bike. As soon as I started to pedal/coast, the rear brake started dragging. I could hear the rotor touching the brakepads. The front brake had no problems.

    So I decided to re-center the rear caliper, with me sitting on the bike. Now, the rear caliper does not make any noise while I am riding the bike, but if the bike is on the stand, or if I am walking my bike, the dragging noise comes back (rotors dragging along the pads).

    This is obviously due to frame flex, but I just cant hit the sweet spot so that the brakes are silent all the time- on the rack, and on the trail.

    Any suggestions to silence the brake would be greatly appreciated.

    edit:: the entire brake system is new, with less than 10miles on them- if this helps anything.

  2. #2
    Meh.
    Reputation: XSL_WiLL's Avatar
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    Are you sure it's just flex? Play in the bearings? QR tight? Etc. Etc.

    What frame? It's possible that it just can't be avoided.

  3. #3
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    Nope.. I would be lying if I said I was sure that its frame flex. What I did was I slowly sat down on the bike, while keeping my eyes on the caliper. The caliper didnt move, but it seemed as if the rotor moved like 1mm or so. Now it could have been the caliper also... but it looked like the rotor.

    Bottom line- something moved 1mm... and closed the gap between the rotor and pad on one side.

    The frame is a Trek 6000. I have not checked the QR. I will do that when i get home. whats the ideal way to center a caliper- sitting on the bike, or off the bike?

    I am not sure how to check for play in the bearings- could you tell me how to do that?

  4. #4
    Meh.
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    Wiggle the wheel side to side. If it feels loose, you have play, if it doesn't, you're fine.

    How much do you weigh? The frame doesn't have to flex much for the rotor to contact the pad.

    If it works while you're riding, that's all that really matters. Who cares if it rubs in the stand?

  5. #5
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    I am 5'11 and I weigh 160lbs. It works while im riding sure, but still, it kindda annoys me that its rubbing when its on the stand... makes you feel as if your bike is not as perfect as it should be.

    Thanks a lot XSL_WiLL. Is there anything else that I could probably do? A pal of mine told me that the drag is being caused due to the new pads. Once they are bedded in, the noise should go away... what do you think about that?

  6. #6
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    I had a problem caused by a loose RDer hanger bolt.

    Check all of your frame bolts and pivots in the rear triangle for tightness??
    I had been wiggling the wheel but it seemed tight enough.

    Yes mine seem to clean up a bit after a few days without playing with them.

  7. #7
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    This is how my brake pads line up with the rotor.

    The first picture shows the alignment when there is no load on the frame.
    Notice the gap between the rotor and the pads. The left pad is totally dragging the rotor. I was shining a flashlight to make the spacing obvious.

    The second picture shows the alignment with me sitting on it. This picture is inverted.
    Notice the gap between the rotor and the pads...
    Attached Images Attached Images

  8. #8
    Nightriding rules SuperModerator
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    Quote Originally Posted by LoneRanger
    I am 5'11 and I weigh 160lbs. It works while im riding sure, but still, it kindda annoys me that its rubbing when its on the stand... makes you feel as if your bike is not as perfect as it should be.

    Thanks a lot XSL_WiLL. Is there anything else that I could probably do? A pal of mine told me that the drag is being caused due to the new pads. Once they are bedded in, the noise should go away... what do you think about that?

    The drag is not caused because of the new pads, but as your buddy says, the rubbing might go away as the pads wear, since they could be a difference between the new pad's position and the worn pad position as the piston compensates for wear....

    However..it sounds a lot like frame flex.... I know it is bothersome... but, I agree with Will, if it works while riding... let it be...

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