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intermittent brake rub - wheel or frame warp - fixable??

dicky tickerdicky ticker Posts: 47
edited June 2010 in MTB workshop & tech
hi peeps

after much annoyance and elimination i have narrowed down an annoying squeak on my beloved baby. all the elimination has been done on tarmac so the bike is under no excessive stress (other than my 15 stone fat censored on the saddle)

i now think it is my back disc rubbing on the pads intermittently.

with the bike in a workstand i cannot reproduce the noise and eveything seems aligned ok - this has been confirmed by my lbs who serviced her. i have found that if i ride with the bike slightly off vertical to the right (more body weight over left pedal) i have no squeak. if i ride with the bike slightly off vertical to the left the sqeak is more common.

obviously i cannot reduce any frame distortion without the help of weightwatchers but would tightening the wheel help reduce this annoying noise?

has anyone had any similar problems or got any other possible solutions
Cheers

Colin

Posts

  • thistle_thistle_ Posts: 6,896
    Is there any play in the hub?

    If the rotor was warped it should be rubbing whichever way you lean. If the frame was twisted I'd expect it to be rubbing all the time as well.
  • thanks thistle

    theres no feelable play in the hub although ive not had the wheel out to intimately check the cones out.

    i'm a bit new to disk brakes and thought that any flex in the frame and wheels would not cause brake rub but i read somewhere it is possible
    Cheers

    Colin
  • supersonicsupersonic Posts: 82,708 Lives Here
    Flex can indeed cause some rub.

    But check the pistons are retracting fully, and the rotor is true. And that the caliper is central to the rotor.
  • thanks supersonic

    being new to discs i asked my lbs to check everything but i suppose i should check the alignment myself

    the real pain is the intermittentcy. its not on every pedal stroke and sometimes it is. the rotor is true so i'm a bit sceptical its alignment but if tolerances are small then i suppose its a possibility.

    shuld have stayed with the road bike me thinks
    Cheers

    Colin
  • nicklousenicklouse Posts: 50,675 Lives Here
    pads can and do rub intermittently.

    might even be some censored on the pads.

    frames do flex. forks do flex.

    if it was a regular rub then a warped disc could be the cause.

    warped wheels would cause nothing as they are nothing to do with disc braking.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • AnonymousAnonymous Posts: 79,667
    could also be a tiny amount of play in the wheelbearings, you only need a little play for it to make some odd noises.
  • i had a similar problem with intermittent rubbing. i made sure all my caliper bolts were tight and i also made sure my QR skewers were tigher than before, this solved the issue, may work for you...
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