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  1. #1
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    Stumpy FSR - Quick Disc Brake Question

    Hey Folks, I just picked up my new 2013 SJ FSR Comp 29er. Thrilled. The last bike I purchased was exactly 20 years older (1993 Rocky Mountain Blizzard), I drove that sucker into the ground. Needless to say, my new SJ FSR has plenty of tech that I am not totally familiar with (yet).

    Full suspension, 130mm travel, through axle, disc brakes, etc etc. All of this is awesome, but new to me.

    I just took my new steed for a buzz around the side streets to feel her out. I love it already. However, I noticed that when I was making sharp turns at speed, my front disc sounds like it is rubbing. I do not have the brake applied when it happens. Like I said, I have never owned a bike with disc brakes so this could be a normal sound, but I'm not sure.

    My LBS told me that these brakes (Avid Elixer 5 RSL) will take some time to break in. I understand that many people have had plenty of problems with Elixer brakes. I have also heard many of you complain about flex with this model of Fox fork. Another thing I should mention is I had to pull the front wheel off the bike to get it in my car, and it took me a few minutes to figure that out, then it took me a few more to get it back on.

    What do you guys think is the cause of this "rubbing" sound? New brakes? Flex in the front end? Misaligned thru axle bolt?

    This is probably a stupid question, but I appreciate any feedback you can provide.

  2. #2
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    I know this "zzing" sound from the brakes when the fork flexes and the pads touch the disc while cornering. It might depend on brake type and brake setup, but i never bothered to investigate any further. When my brakes work i rarely touch them (you know, a running system...).

  3. #3
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    New brake pads by definition will be thicker, meaning less space between them and the brake rotors. So, at first problems of this type are most noticeable.

    However, this is a flex issue, so you should look at that first. There's a chance that re-mounting the front wheel would solve it if you left some play in it somehow. If that doesn't help, I'd have your bike shop check the front hub and fork for issues.

    If you are asking if this is expected with new technology on bikes, no. I would want it addressed.

    (Also, if you are a particularly big guy, or Clydesdale rider, that's another factor to consider, as other options may be better suited to you.)

  4. #4
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    If the rubbing sound only happens when you're on the bike, it could be fork flex. Hop off the bike and give the wheel a spin. If it still rubs, your caliper is probably just not aligned properly. However, if it only hits the rotor at certain spots, your rotor could be slightly bent. If that's the case, give the wheel a spin and look at the caliper where the pads sit...you should be able to visually tell if the rotor is bent. It's pretty hard to mis-align a thru axle. There's really only one way they go back in.

    If you can't figure it out, I would suggest taking it to the shop you bought it from. I've never seen a brand new bike come through the shop I work at with hydraulic brakes that rubbed constantly as part of the "breaking in" process. More often than not, it's a caliper adjustment issue or slightly bent rotor..

  5. #5
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    Brake in my @ss !! The 5's on my fsr elite 29 are the worst set of Avids I've ever had,can't wait to replace them. Squeaking is there 90% of the time and be sure not to ride a 10 seconds downhill trail right after you've already rode one as you will only have 50% breaking power....

  6. #6
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    Quote Originally Posted by Devastazione View Post
    Brake in my @ss !! The 5's on my fsr elite 29 are the worst set of Avids I've ever had,can't wait to replace them. Squeaking is there 90% of the time and be sure not to ride a 10 seconds downhill trail after you've already done one as you will only have 50% breaking power.
    Sounds like you have a bad set. My Elixir 5's work fine, absolutely no squealing or fade in braking power.

  7. #7
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    Maybe it's my wrenching skills or bad luck, but any set of brakes (juicy 7, shimano deore, elixir cr) I've owned have rubbed just a touch when brand new or when I replace pads.

    The front rotor on my brand new (just picked it up last night) evo comp rubs just a *smidge* rolling around the neighborhood.

    IMHO a little bit of rotor rub isn't a huge deal and takes care of itself with one good ride. This, of course, is assuming everything is functioning normally and the rotor isn't bent. \

    I wouldn't go too crazy over a ittle rotor sound til you've given it a good ride or two...
    Taking it easy for all you sinners.

  8. #8
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    Quote Originally Posted by jubilee View Post
    Maybe it's my wrenching skills or bad luck, but any set of brakes (juicy 7, shimano deore, elixir cr) I've owned have rubbed just a touch when brand new or when I replace pads.

    The front rotor on my brand new (just picked it up last night) evo comp rubs just a *smidge* rolling around the neighborhood.

    IMHO a little bit of rotor rub isn't a huge deal and takes care of itself with one good ride. This, of course, is assuming everything is functioning normally and the rotor isn't bent. \

    I wouldn't go too crazy over a ittle rotor sound til you've given it a good ride or two...
    I agree with your points if the rubbing occurs all the time, and happens when not sitting on the bike. It can definitely be a pain to get new brakes set correctly, and when pads are new (and thicker) it's just a bit harder.

    But I disagree with you in this case. The OP is citing that he only hears the rub on high speed turns. This means some something is flexing under the added forces in this situation. Not saying it's earth-shattering, and it may go away as the pads wear, but I still think it's a flex issue, and not a brake-dial-in issue. I would have written "brake-break-in" issue, but that's just confusing.

  9. #9
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    Stumpy FSR - Quick Disc Brake Question

    The gap between pad and rotor with disc brakes is quite small. Whenever you remove a wheel and then refit it the rotor can potentially end up misaligned with the pads if the skewer tension isn't exactly the same each time.

    With a Fox QR15 thru axle fork there's a threaded adjuster on the fork leg which allows you to fine tune the tightness and lever position of the thru axle. The thru axle threads into it. The adjuster unfastens with a small allen key and then you move it around one numbered notch at a time. Once you've adjusted this so that the thru axle is fully tight you should be able to take the wheel on and off without needing to adjust the brake caliper afterwards, as the thru axle will be the same tightness each time. If your brake is rubbing when cornering changing that adjuster setting will tighten everything up, making it harder for the fork to twist under load. On my Fox F100 Terralogic QR15 fork the adjuster needed turning 3 to 4 notches from stock before the thru axle was able to tighten fully.

    After fully tightening the thru axle you'll need to adjust the front brake caliper so that the wheel spins freely without any rotor rub. The most successful way is usually to do this by eye. Loosen the two caliper allen bolts a small amount, just enough that you can push the caliper left and right with pressure from your thumbs, but not enough that it's fully loose and rattling. Using small adjustments align the caliper so that it doesn't rub when spinning the wheel, and then fully tighten the caliper bolts again. Putting a sheet of white paper on the floor beneath the bike can be helpful for looking down on to spot the pad/ rotor gap.

    Once you've done that it should hopefully stay trouble free for a while. If you can't get the rotor to spin freely then it could be that the rotor has warped. You can true a brake rotor by carefully bending the rotor to straighten it out again.

    Brake rotor truing
    Disk Brake Rotor Precision Truing

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  10. #10
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    Thanks everyone for all the comments. The "zzzing" was noticeable only when turning sharply at high speed, so I thought it could have something to do with the tightness of the front axle, or inherent flex in the fork. I had it out on the trails today, and didn't hear anything over and above the trail under my wheels. I suspect that adjusting the dial as suggested by WR304 should tighten everything up. Thanks again.

  11. #11
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    I have a 2013 Stumpy fsr carbon expert, I get the exact same thing. It's just slight flex in the fork and is nothing to worry about. I never notice it while I'm out on trail, only when I'm turning, usually at fairly high speed, on the road.

    I also used to get it on my last bike, a 2012 giant trance xo.
    Real men do it in the dirt

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