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Rubbing disc brake

FergySteveFergySteve Posts: 82
edited April 2013 in MTB workshop & tech
Hi all, I've had a look around youtube and this forum and have tried the fixes that I've found, but still have some annoying rub issues. Maybe you can help? Apologies if this has been covered, but I did spend a bit of time looking - promise!! :D

On the rear brake (Avid Elixir 1) of my girlfriend's bike, the pads seem to rub on the disc slightly all the time. I have re-centred the caliper which has given some improvement, but it's still rubbing slightly. I don't think the rotor is bent and it looks to me that the pads aren't retracting away from the disc enough, so I can't see a gap between the pad and rotor.

I've tried removing the caliper from the frame, and taken the pads out and used a plastic tyre lever to press the pistons back into the caliper, thinking maybe they've advanced too much, but when i push one piston in, the other comes out. :? I don't have much experience with hydraulic brakes, so not sure if this is normal? If so, is there a trick/knack to pushing both pistons in at the same time? I tried with two levers, but my efforts were just comical! :oops: I didn't want to stick a screwdriver or anything in there in case I damaged the pistons.

Any help appreciated.
2015 Specialized Tarmac Expert Ultegra
2016 Focus Mares CX Ultegra
2016 Specialized Stumpjumper HT Comp Carbon 29
2012 Boardman Road Race 105
2013 Specialized Hardrock Disc

Posts

  • The RookieThe Rookie Posts: 27,804
    Use an Avid pad spreader (wedge), failing that a table (not kitchen) knife and twist it, yes normal for one to come out as the other goes in.

    Centreing Avid calipers can be a PITA as the CPS washers mean it often moves as you tighten the bolt, you need to nip each bolt up in turn a bit more and a bit more until they are tight.
    Current steed - Whyte T129, 2013 frame, mongrel Revelations, Giant dropper, Stans S1 wheelset. 12, Magura Trail Sport brakes, 1x11. 12.8Kg
  • maringirlmaringirl Posts: 195
    Also sounds like a little too much fluid in the brake if one piston is coming out when you push the other - not unusual in an Avid. let a little out and then reset pistons again.
  • Ok, thanks. :)

    Maringirl - is that what the little torx screw is for on the caliper? Would I have to bleed the system if I did that? I don't have a kit, so I'd like to avoid that if possible.
    2015 Specialized Tarmac Expert Ultegra
    2016 Focus Mares CX Ultegra
    2016 Specialized Stumpjumper HT Comp Carbon 29
    2012 Boardman Road Race 105
    2013 Specialized Hardrock Disc
  • The RookieThe Rookie Posts: 27,804
    Let the fluid out using the little torx screw on the lever, less chance of letting air in that way, then no need to bleed.

    Overfilling is caused by bleeding without having the pistons pushed right back.
    Current steed - Whyte T129, 2013 frame, mongrel Revelations, Giant dropper, Stans S1 wheelset. 12, Magura Trail Sport brakes, 1x11. 12.8Kg
  • Chunkers1980Chunkers1980 Posts: 8,035
    If they've worked in the past correctly, and you've not bled them I wouldn't not be letting fluid out
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