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  1. #1
    Freelance Whatever
    Reputation: chowdownca's Avatar
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    XTR adapter for post mount rear

    I have a SJ Comp Carbon 29er and I have my XTR 985's in hand and ready to go...except for the rear...I'm trying to find the disc brake caliper adapter that I need to use for the post mounts on the frame and can't seem to find it ANYWHERE. The I/S adapters are available, but post mounts? Am I missing something? For right now, I have the longer mounting bolts/spacers from the Elixirs holding it down. Anyone have any advice? I'm running a 160 rotor on the rear and it definitely needs some kind of spacer/adapter to ride where its supposed to. Thanks in advance...
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  2. #2
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    M985 caliper is post mount.
    to mount to a post mount fraem you shouldnt need any adapters. unless your frame is designed for a 140mm rear rotor then you'll need a Front 180mm post - post adapter to space the caliper up to 160mm spec.


    this one.
    http://techdocs.shimano.com/media/te...9830667774.PDF

  3. #3
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    Bike was stock with 160's..

    ..but they were Elixir Rsl. The rear had the longer mounting hardware with spacers and the Avid align washers. Would that indicate that the frame was designed for compatibility with 140's, spec'd with 160's and would need the front 180 post to post adapter? Alrighty then... Thanks!
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  4. #4
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    Quote Originally Posted by Dover View Post
    M985 caliper is post mount.
    to mount to a post mount fraem you shouldnt need any adapters. unless your frame is designed for a 140mm rear rotor then you'll need a Front 180mm post - post adapter to space the caliper up to 160mm spec.


    this one.
    http://techdocs.shimano.com/media/te...9830667774.PDF
    Yeah, now try finding that part. I call the shops with that part number and they can't help me. I can only find a couple onlne and they are both in Europe...

  5. #5
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    I posted this over the in the Specialized forum as well. Their advice was something that I've already done, which is to use the stock Avid spacers/bolts from the Elixirs to get the caliper to the correct location. My next question is: will this create torque/stress issues that could damage the post mounts on the frame? Does the adapter disperse some of these forces evenly to prevent any damage to the post mounts?
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  6. #6
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    Im running into the same issue...I have a 2011 Epic, installing Shimano M785 but not finding the appropriate spacer for the install. Chow, what did you wind up doing to make this work? Im thinking about using the Avid spacers and grinding them down, just doesnt sit well for any type of exact tolerances

  7. #7
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    What did I do?

    I ended up using the stock hardware from the Elixirs. The beveled washers moved things around enough that I could at least get the caliper aligned. It worked pretty good. It wasn't perfect, but it was good enough. But in the end, I did notice that the piston on the inboard side of the caliper was pushed out further than the outboard. Don't know if this was an install issue, bleed issue or both.
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