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  1. #1
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    XT 775/xfusion Slide brake rub

    I have a Niner Sir 9. I was running rigid with bb7s. I swapped to an xfusion slide 29 fork and bolted the bb7s in place. No trail rides in that form...just up and down the street. Everything was fine. Picked up some used XT 775 brakes in great condition. Bolted them on. Adjusted them. Everything was fine. Hopped on and started down the driveway and heard rubbing. I've recentered them. Tightened the QR. I've gotten it to be minimal. Usually it starts when turning, but not always. In the work stand they are true and centered and spinning easily. When I get on, the rubing starts. It's not unrideable...they don't rub that badly. I can't feel it when I ride, only hear it. And its annoying. Any ideas?

  2. #2
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    Nothing?

  3. #3
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    Is the rotor true?

    If it is mainly when riding, sounds like it could be fork flex causing it? Is it constantly rubbing? Only when wheel rotating? When pulling on the bars?

  4. #4
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    Just rubs at a certain area. Rotor is pretty true, but it might need tweaking.it doesn't do it on the stand at all. Only when riding and even then not all the time. It starts when I corner and then continues. I'm afraid it's fork flex which is saddening. Might be the hubs, but they weren't causing any problems before the fork change.

  5. #5
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    Sounds like fork flex to me. I am guessing that it is not the new slide's with the thru axle.

    Anyway, it might be annoying, but that is as far as it goes. Just ride it and enjoy it.

  6. #6
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    Already have...lol! No through axle, but it rides pretty sweet anyway. Thanks. I may true the rotor a bit, it ride it I shall.

  7. #7
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    Check for thick blotches of paint on the fork dropouts. Back in my shop days we'd sometimes get a bike with the same problem you've described; no brake rub in the stand but it scrubs when you get on the bike and ride it. More often than not the cause was a thick blob or blotch of paint on the dropouts that prevented the hub from seating consistently and/or the QR from clamping securely. Even if the QR is tight, everything can and does shift around just enough to let the brakes rub when your weight is on the bike. File off the paint blob and everything works the way it should.

    Other possible causes are a slightly loose hub, or in rare cases, just a stupidly tight clearance on the brakes. Check the hub, reset the pistons in the brake calipers, and see if it reduces or eliminates the rubbing when you're riding. If you're still having the same issues after doing all the above, then it's likely a flexing fork issue.

  8. #8
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    Is your hub loose?

    Shimano brakes also suffer from sticky seals from time to time. If you have one of the little yellow blocks grind it in half, down to the ears. Then put it into the brake with pads removed and pump the lever up. This will pump the piston almost all the way out but keep it from coming out. Then you can remove the block and clean the piston with alcohol and lube it with Shimano's mineral oil. Then do the other side. I normally have to do this a couple times a year to keep brakes in top form.

  9. #9
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    I can't find any play in the hub. I my drop by the lbs to have them check it. Couldn't find any globs of paint. I did rebleed the brakes and pushed the pistons back in. Hopefully I can get it out on the trail today or tomorrow and check it out.

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