Shimano xt 785b rubbing, brand new- Mtbr.com
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  1. #1
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    Shimano xt 785b rubbing, brand new

    So I am building up a "new" bike with full 2014 XT and can't for the life of me get my wheels to "spin" without excessive rubbing. Back in the day I used to be a bike wrench so it's not like I don't know what I am doing. Brakes are brand new XT 785b, rotors are Magura Storm SL, I am also using a Shimano adapter. Brakes have the metal ice tech pads. The rotors are new, and warp free. I have tried the squeeze and tighten method, resetting the pistons, and would love to try the shim method but the pads are too close to the rotor to get anything in there. I have also cut the lines and bled the system with the yellow block. Would much rather be riding than scratching my head so I appeal to you all for any more ideas, tips, or advise.

  2. #2
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    My slx on my karate monkey did this.

    No room to shim, pistons reset. So...

    I ended up sighting them with the help of a bright flashlight and positioning the caliper by hand the best I could so the pads and rotors would clear.

    It worked, but it's only been a 20 mile rd ride since. We'll see when the grit and grime and bouncing around on trail hit them.
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  3. #3
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    maybe XT IceTech rotors would have been a better choice...not a peep from my lowly M615 CenterLock poop... especially considering they are like $40 everywhere distinct possibilty that the two just don't like each other...other than that, you, or your LBS gotta get the calipers right...what else can it be
    Attached Thumbnails Attached Thumbnails Shimano xt 785b rubbing, brand new-dsc01901.jpg  

    Shimano xt 785b rubbing, brand new-dsc01909.jpg  

    2014 Nail Trail 29...

  4. #4
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    Quote Originally Posted by time229er View Post
    maybe XT IceTech rotors would have been a better choice...not a peep from my lowly M615 CenterLock poop... especially considering they are like $40 everywhere distinct possibilty that the two just don't like each other...other than that, you, or your LBS gotta get the calipers right...what else can it be
    I need red hoses.

  5. #5
    clk
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    some rotors seem to be slightly thicker than others

  6. #6
    clk
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    possibly have too much fluid in the brakes from when you bled them

  7. #7
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    Quote Originally Posted by MSU Alum View Post
    I need red hoses.
    no, no, you do not...needing and wanting are two totally different paths and I kinda like being out here on the fringe alone...and what about the OP's query...
    Attached Thumbnails Attached Thumbnails Shimano xt 785b rubbing, brand new-dsc01911.jpg  

    Shimano xt 785b rubbing, brand new-dsc01906.jpg  

    Shimano xt 785b rubbing, brand new-dsc01698.jpg  

    2014 Nail Trail 29...

  8. #8
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    160? 180? Front or rear? If it's front, you would really need angular spacers between the bolt head and the caliper.

  9. #9
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    Quote Originally Posted by time229er View Post
    no, no, you do not...needing and wanting are two totally different paths and I kinda like being out here on the fringe alone...and what about the OP's query...
    He needs red hoses, too!

  10. #10
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    Quote Originally Posted by thickfog View Post
    I ended up sighting them with the help of a bright flashlight and positioning the caliper by hand the best I could so the pads and rotors would clear.
    This would be my first plan of action...confirm where the contact is taking place and attempt to rectify.

    Second initial thought would be too much fluid in system, but seeing that you performed a bleed (assuming properly) and you are SURE that's not the issue.

    I'm not buying the "rotor is too thick" concept. Prolly not the problem.

    I've got to be thinkin' loosen, squeeze and incrementally tighten each of caliper bolts alternately until tight. I have seen getting one bolt tight, then the other, place a tweak on the caliper and not rest true with the rotor.

    Good Luck, and report back your results.
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  11. #11
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    Here is a progress report: I removed bleed plugs from the levers and let out some fluid, that got me in the ball park for the back. I was then able to adjust it out (rear). On the front, it's a little different. I am not sure if my post mounts are lining up properly. I am going to try putting a thin washer under the caliper. At least it spins! Still noisy though, I finished the build today and took it out for a "shakedown", everything is perfect except the front brake. I have not had this problem when the fork (RS Revelation U-Turn air) was on my other bike (Brodie) with their Hayes brakes. I know that if I were to let more fluid out, it wouldn't do anything, but I will try it anyways, maybe I will be surprised. Do you think that I just have to bed them in a little more before I try anything else, and see if that does anything? Will post pics the the completed bike in the near future...

  12. #12
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    Again, are you using 160 mm or 180 mm rotors? If 180, do you have a pair of angular spacers between your bolt heads and the caliper? With 180 mm, without spacers, your post are essentially twisted downward because the 160-to-180 adapter is slanted.

  13. #13
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    I have 160mm rotors front and rear. Where are these angular spacers available? Would be good to have something like that in my toolbox.

  14. #14
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    Sounds similar to my issues that I've since figured out. One is the "angular spacers" basically a concave and convex washer pair, use them regardless of rotor size. Second is tightening mounting bolts not one at a time but gently snug bottom then top, then repeat tightening a bit more then 3rd time is tighten fully. Didn't have to use shims (did have to drain some fluid but was my own dumb fault) or anything. Also not sure your forks, but if on 9mm qr make sure its insanely tight before doing anything.

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  15. #15
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    Yes, I have 9mm QR forks. Yes, the QR's are VERY tight. I don't think I can use the concave/convex washers on my forks with a 160mm rotor-too much spacing. I have got it "okay" and plan to do some riding to bed-in the pads/rotors once the weather gets a little more friendly. Perhaps the issue will fix itself, at least, I hope so.

  16. #16
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    Well, I have bed in the brakes, rear is PERFECT, front... still rubbing. I have tried removing the 1mm washer I put under the lower tab, tightening the QR some more and re centering (many times). But still the the "swooshing" rub sound that is driving me crazy. The hold the lever and tighten method of centering bring me the worst results. I am really thinking that there may be an issue with my PM tabs needing to be faced, but don't have the cash to take them into a machine shop. My next move is to verify that the rotor is true by removing it and putting it on glass to verify. As it is all new parts from Jenson and I live in Canada, returning could be quite the ordeal that I would rather avoid. Has anybody had problems with Magura Storm SL rotors, either with XT 785, or warped from new? I will also swap rotors front to rear and see if that helps. More ideas would be most welcome please.

  17. #17
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    I've found with the "squeeze and tighten" method that any stress on the brake line (from frame clips) will knock it out of whack, so I disconnect the lines from the frame/fork before adjusting. Then use the 3 step tightening method mentioned above.

    If it still rubs then I do it by sight with a bright flashlight, loosen the caliper bolts just enough to move them a touch by tapping with a plastic screwdriver handle.

    [tangent]
    Is that front brake post spacer upsidedown, time229? I've never used one, so not sure, but it just looks "wrong"...

    In the shimano tech-doc, the drawing looks like the long post on the fork is on bottom, in your photo the long post is on top:

    http://techdocs.shimano.com/media/te...9830702216.PDF
    [/tangent]
    Last edited by shupack; 04-22-2014 at 04:19 PM. Reason: top/bottom upsidedown...

  18. #18
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    Quote Originally Posted by HerrDoctorSloth View Post
    The hold the lever and tighten method of centering bring me the worst results. My next move is to verify that the rotor is true by removing it and putting it on glass to verify.
    Your first statement in the quote leads me to think your rotor isn't true. However, it's easy to determine if it's true with out removing it. Find some way to grasp an object or just use your finger steady against the chain stay and next to rotor as you rotate the wheel and confirm if true enough. All I use is my finger.

    You can just use a crescent wrench to true it unless you care to plunk the change on a truing fork. Not necessary though if you don't expect to be doing it very often.
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  19. #19
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    I am running 160mm rotors, and have not posted a picture. No adapter on the fork. To my bad eyes it looks like the caliper is leaning to the inside, there are also paint chips on the face of the post (have no clue how that may have happened). Was also contemplating removing the rest of the paint with a razor blade as to not remove any material other than paint. The finger true method is pretty cool, but since I am planning on swapping the rotors, I will check it against a piece of glass and true it if necessary. I will be swapping to other tires, so I might as well since the wheels will be off anyways.

  20. #20
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    Quote Originally Posted by HerrDoctorSloth View Post
    I am running 160mm rotors, and have not posted a picture. No adapter on the fork. .

    sorry, I realized it was someone else's photo right after first submit... I edited it, but I guess you read the post in the email.

    To my bad eyes it looks like the caliper is leaning to the inside, there are also paint chips on the face of the post (have no clue how that may have happened). Was also contemplating removing the rest of the paint with a razor blade as to not remove any material other than paint. The finger true method is pretty cool, but since I am planning on swapping the rotors, I will check it against a piece of glass and true it if necessary. I will be swapping to other tires, so I might as well since the wheels will be off anyways
    if the frame to caliper mating surface is not flat, that can/will cause issues like you describe because the pads will be cocked towards the top of the rotor on one side and the bottom on the other, effectively tightening the clearance. A razor blade can easily cut into aluminum, a gasket scraper ($5 at autozone) should do the trick.
    Last edited by shupack; 04-23-2014 at 02:44 PM.

  21. #21
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    another sugg.

    try removing the pads,install the yellow pad spacer,crack the CALIPER bleeder just enough to allow excess to drain,then tighten the bleeder.reinstall the pads but make sure the pistons center to the rotor when squezzing the lever.if one piston is slow moving it could cause the pads to not make rotor contact equelly.

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