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Rear wheel puzzler

redstar1redstar1 Posts: 15
edited November 2013 in MTB workshop & tech
Have a 2013 Rockrider 8.1 and having an issue with back disk brakes scraping when riding. When I have the bike upside down there's no issue at all, disks do not rub against the calipers at all. Issue only occurs after riding for 10-15 minutes. There is an awful scraping noise especially at low speeds. Sometimes when I use the back brakes fairly hard the issue will go away for a while but always seems to come back.

Obviously there could be a multitude of causes but anything obvious I can check myself?

Posts

  • supersonicsupersonic Posts: 82,708 Lives Here
    Check rotor is true, and caliper is aligned correctly. Also check the pads are moving equally.
  • nicklousenicklouse Posts: 50,675 Lives Here
    also check the hub bearings for play.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
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  • jimothy78jimothy78 Posts: 1,407
    Reckon Nick's got it sussed if there's really a discrepancy between upsidedown and riding positions.

    If it's not that, then check for sticky calliper pistons as well.
  • make sure the rear wheel is tight in the dropouts too.
  • If not loose bearings, look for soft rear skewer or dodgy dropouts that let the back wheel move in the frame under load.
    Could also be a broken axle.
    Also check that the brakes are not too full and pumping up after use due to heating or the possibility of some air in the brake lines.
    Moisture may have been absorbed into the brakes if it is DOT fluid based and not been flushed since new, and now the system is too full with no room left for expansion with heat.
  • cooldadcooldad Posts: 32,599
    There is no way a 2013 bike needs the brake fluid changing.

    Brakes often make noise, sometimes it's just annoyingly normal.
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  • The RookieThe Rookie Posts: 27,804
    Moisture may have been absorbed into the brakes if it is DOT fluid based and not been flushed since new, and now the system is too full with no room left for expansion with heat.
    Very unlikely to impossible, firstly a bike system has the fluid sealed from atmosphere so no moisture can get to the fluid to be absorbed, secondly as the fluid absorbs moisture it actually reduces in volume initially and thirdly, even open to atmosphere it's unlikely to be an issue by now.........
    Current steed - Whyte T129, 2013 frame, mongrel Revelations, Giant dropper, Stans S1 wheelset. 12, Magura Trail Sport brakes, 1x11. 12.8Kg
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