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  1. #1
    mtbr member
    Reputation: shanem's Avatar
    Join Date
    Apr 2008

    Serious problems bleeding XTR M985 brakes

    I have been screwing with these brakes for far too long at this point. I bleed them and they feel fine with the bleed block in place. As soon as I replace the block with the pads and put my wheel back on.....The lever bottoms right out to the bars. What the hell gives? Anyone have an idea of what's going on here? And how to fix it. Thanks


  2. #2
    mtbr member
    Join Date
    Nov 2005
    did you pull the lever repeatedly after removing the bleed block, to move the pistons and pads closer to the disc?

  3. #3
    mtbr member
    Reputation: shanem's Avatar
    Join Date
    Apr 2008
    Yes. That firms it up a bit but still nowhere near enough

  4. #4
    mtbr member
    Join Date
    Jul 2011
    I think B.BL has the solution, but perhaps you just need more of it?

    I'd recommend doing maybe 10 quick squeezes of the lever, then hold the lever down as far as it'll go for 10-20 seconds. Then do a bunch of quick squeezes again followed by a long hold. Repeat as necessary. You should feel the lever continue to harden up.

  5. #5
    El CicloPath!!!!!!!
    Join Date
    Nov 2012
    If the lever is still bottoming out, then it might either be a bad bleed or there is still air in the system.

    When bleeding , use the thick block, but before you put on the wheel, use the pad spacer to get the correct spacing. Do the repeated hard squeezings with the pad spacer in place, the orange plastic one.

  6. #6
    mtbr member
    Join Date
    Mar 2006
    I guess that you bleed your brake according to manual.I did that also.Bleeeding from the caliper with syringe,using gravity bleeding with shimano oil funnel for a half a dozen times with proper shimano spacer at the caliper and result is lot of free stroke and not so good "feedback" on the lever.
    There is a few things that I notice on the caliper.
    First,when pads are removed there are lot of space between pistons,much larger comparing with other brakes,and second,even with the new pads pistons are out for a few mm from the caliper,normaly on my previous brakes I need to push pistons all the way in to put new pads so they dont rub disc.
    So I make a little experiment,and things works,a simple and cheap solution how to boost up performance of M985 brakes.
    I decide to make a spacer,that will enable piston to stay all the way in before any lever action.
    The easiest way to make spacers is from a worn brake pads.
    Remove all the friction material and make backplate app. 1.3-1.4 mm thick.
    Put each of the tuned backplates between brake pad and piston.
    This simple idea will cut free stroke at half,feeling on the lever will be significantly stiffer,believe me you will notice on the lever when pads touch the rotor.
    Also,an extra backplate ensures that brake pads always will be parallel to the disc.
    Try and tested,for me it is one finger braking in all situations with 160 mm rotors.

    Recommend an aluminum backplate (from resin brake pads) for your home tuning,because aluminum is better for heat dissipation.
    Last edited by baraccuda; 07-23-2013 at 05:05 PM.

  7. #7
    mtbr member
    Join Date
    Apr 2009
    Yea, this is super frustrating. I even bought the special funnel, a special syringe kit from a third party vendor, and I still had troubles. The syringes just don't inject smoothly enough and sometimes take alot of force presumably due to the friction of the plunger (?). Someone mentioned o-ring type syringes were better in this regard.

    Anyway, I believe I got all the air out of the system with all this gadgetry. I had the same problem where it felt great with the bleed block in but then with the pads and rotor back on, I had a super long lever. I did "adjust" the pads with the red plastic insert first.

    The solution was to take the rotor and red plastic insert out and pull the brake lever once (in my case) completely to the handle bar. Presumably, this allowed the pistons to auto-adjust enough to give a great lever feel but not drag on the rotors when re-installed.

    FWIW, this is with the Trail "Servo-Wave" brakes which, after trying the Race brakes, I'm not sure I'm in love with anymore. I think the Race brakes give a more consistent feel to the lever whereas the Trails have the funky cam feeling. I guess it's personal preference.

    So, in summary, pull the lever w/o a rotor or spacer in there to let the pistons auto adjust. This experience was with used pads also which may make a difference. Maybe the red spacer is designed to work when you're installing new pads only.

  8. #8
    mtbr member
    Join Date
    Jan 2008
    Install the caliper on your bike and ditch those spacers for now. Keep the bleed port on the caliper closed.

    When you have the funnel in the top of the lever (fill the funnel half full with mineral oil) un-screw the free stroke screw all the way then squeeze the lever a few times until the trapped air comes out.

    Tighten the free stroke screw all the way, squeeze the lever a few times.

    Then loosen it again and squeeze, more air will come out.

    Repeat this step several times, often a lot of air will get trapped in the free stroke adjustment area inside the master - also make sure you move the bars / lever around while bleeding to ensure the trapped air moves out.

    Take your bike for a lap around the driveway, then do this process again.

    They will then be perfect.

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