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  1. #1
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    Brake rub under load?

    Picked up a new Fatboy last week. I am getting some disc rub under load. Not under braking but going into turns like on a flow track. I am not the smallest guy out there but at 220, could the carbon fork be flexing that much? The hub feels solid. Anyone else run into this?

  2. #2
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    Sounds like the fork is flexing.

  3. #3
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    Normal.

  4. #4
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    Make sure axle is tightened properly and brakes are centered properly. Beyond that it's normal, doesn't take much flex to cause rub.

    Sent from my XT1565 using Tapatalk

  5. #5
    IH, HYHT.
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    I started having that this weekend, turns out my hub needs bearings.
    The most expensive bike in the world is still cheaper than the cheapest open heart surgery.

  6. #6
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    So, any other suggestions? I replaced the QR with a DT Swiss RWS and cranked it down. I took it for a test ride and at decent speed, it will still rub going straight and worse with the slightest swerve. Could the caliper be sitting a bit too low?

    The Gemini brakes have very little clearance from side to side. Different brakes?

    Would a thru axle fork/hub fix the issue?

  7. #7
    since 4/10/2009
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    Thru axle is always stiffer than QR. I won't buy another mtb with QR. Definitely not a fatbike. The extra width of the hub spacing just makes QR worse.

  8. #8
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    Quote Originally Posted by Terry66 View Post
    So, any other suggestions? I replaced the QR with a DT Swiss RWS and cranked it down. I took it for a test ride and at decent speed, it will still rub going straight and worse with the slightest swerve. Could the caliper be sitting a bit too low?

    The Gemini brakes have very little clearance from side to side. Different brakes?

    Would a thru axle fork/hub fix the issue?
    Center your caliper. Loosen the 2 bolts on the caliper. Squeeze the front brake and hold it while tightening the caliper bolts back up. If you still have noise under load while swerving it's the fork flexing and it's normal. I wouldn't worry about.

  9. #9
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    Quote Originally Posted by prj71 View Post
    Center your caliper. Loosen the 2 bolts on the caliper. Squeeze the front brake and hold it while tightening the caliper bolts back up. If you still have noise under load while swerving it's the fork flexing and it's normal. I wouldn't worry about.
    Centering the caliper is where I start once I check that everything is tight. Too often people are just centering the pads over the rotor without regard for whether the pistons/pads are equally extended. Retract the pads and center the caliper body over the rotor. The pistons/pads will usually find their place.

    If your brakes rub when just going straight then they are not set up properly.

  10. #10
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    Quote Originally Posted by Terry66 View Post
    So, any other suggestions? I replaced the QR with a DT Swiss RWS and cranked it down. I took it for a test ride and at decent speed, it will still rub going straight and worse with the slightest swerve. Could the caliper be sitting a bit too low?

    The Gemini brakes have very little clearance from side to side. Different brakes?

    Would a thru axle fork/hub fix the issue?

    Are the brakes centered? Sounds simple, but simply loosening, squeezing and retightening does NOT center the brakes for me. They migrate over when you tighten the bolts in the direction of torque and keyed indentations further prevent them from achieving an actual "center". This is why I liked the old style brake mounts, they could be spaced exactly, but they did rely on precision surface specs as the disadvantage. I usually have to manually "push" the caliper in the opposite direction of torque when tightening. Kind of takes 3 hands. I was getting some noise/drag during a few recent installs/adjustments. After the "loosen squeeze tighten" method, they weren't even close to center.
    "It's only when you stand over it, you know, when you physically stand over the bike, that then you say 'hey, I don't have much stand over height', you know"-T. Ellsworth

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  11. #11
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    X2, the squeeze and tighten method is a giant failure in my book. I set a light on the ground or behind so i get light in the gap between the pads and rotors, set centering visually and I stopped having issues. And both my bikes are QR rear (I just tighten them to the point it's painful to try and release the qr again)

    You can also run into this on hydraulic brakes in the cold, one piston can stick a little. Have to reset pistons and possibly flush/bleed them as it could be contamination in the fluid that's not a problem till the fluid thickens due to the cold. Had that happen once on my Shimano brakes on my 29er. Part of why I prefer avid bb7 for winter use. Not the quietest brakes but hot or cold outside, they work just the same.

    Also check and make sure hub bearings aren't loose. Play in the bearings will cause all sorts of issues.

    Final thing, check and make sure your rotor doesn't have a bend in it, doesn't take much of one (and it happens rather often for 100s of reasons ) to cause rub when the frame flex

    Sent from my XT1565 using Tapatalk

  12. #12
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    Thanks for the feedback. Brakes are fine. Pretty sure it is the fork flexing. Gonna swap it out with an aluminum Beargrease fork I have in the garage and hit the trails tomorrow.

  13. #13
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    I'm 275 and was on chromo enabler forks without any issues unless turning instead of leaning like I should be. And that was barely. I'm on CF forks no and no issues.

    Good luck swapping forks out that may do it for you but I demoed a fat boy last weekend and no issues there either (that I noticed)

    Sent from my XT1565 using Tapatalk

  14. #14
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    Totally normal. Wide hubs + big rotors = light rubbing around corners. You can futz around with the calipers and maybe eliminate the occasional slight noise but who really cares.

  15. #15
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    This can be exacerbated by using a big rotor. Are you using a 160 or something silly like a 200?

  16. #16
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    Quote Originally Posted by Volsung View Post
    This can be exacerbated by using a big rotor. Are you using a 160 or something silly like a 200?
    Yeah, big rotors plus QR = fail (at least with regards that it takes less actual flex to create really annoying brake rub you can't adjust away).

  17. #17
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    Quote Originally Posted by Harold View Post
    Yeah, big rotors plus QR = fail (at least with regards that it takes less actual flex to create really annoying brake rub you can't adjust away).
    I have been dealing with the same issue for over a year on my Fatboy Comp Carbon. I drives me insane. I was 220 when I purchased the bike and now at 185, but still getting noise. It is almost like a ringing sound. I worked with Specialized and the LBS for 6+ months to resolve, but could never get the issue to go away. I continue to ask other fat bike riders if they are having the same issue, but the only ones seem to be riding the Fatboy. Currently considering moving to Trek Farley or Carver.

  18. #18
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    I had rubbing at speed with my fatbike. Turned out the calliper was too close to the rotor radially. (and the pads where to far in on the disc). Two washers under the callipers solved that.


    Peace!

  19. #19
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    Quote Originally Posted by craiglance View Post
    I have been dealing with the same issue for over a year on my Fatboy Comp Carbon. I drives me insane. I was 220 when I purchased the bike and now at 185, but still getting noise. It is almost like a ringing sound. I worked with Specialized and the LBS for 6+ months to resolve, but could never get the issue to go away. I continue to ask other fat bike riders if they are having the same issue, but the only ones seem to be riding the Fatboy. Currently considering moving to Trek Farley or Carver.
    If it indeed it is a problem caused by the QR the fatboy now has a thru axle on any model above the Fatboy SE

  20. #20
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    I had same issue with brakes rubbing when hammering at high speeds. Downsized rotors and it helped, but still occurs on the back wheel. It looks to be just a flexing issue with the carbon frames from Specialized. It is too bad, because other than that issue, it is the most fun I have had on a bike ever.

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