Frame/wheel flex and disc brake problem

Discussion in 'Mountain Bikes' started by Christophe, Jan 27, 2004.

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  1. Christophe

    Christophe Guest

    Hi all,

    This is the first time I post here, I'm Christophe 27 year old, riding a 03 Specialized FSR disc in
    the french alps.

    I post this e-mail cos I'm experiencing exactly the same trouble as yours with exactly the same bike
    and component setup.

    My dealer already exchanged the frame and wheel, and got the deore disc brake checked by shimano
    (no issue there). I can reproduce the issue on my wife's FSR also, with my wheel and brake
    mounted on it.

    I currently do no what to do anymore, because this looks like a "built-in feature" of the
    stumpjumper FSR to have that kind of flex.

    Did you manage to fix this by changing a skewer or getting a better hub than the deore disc?

    Question for all, do you experience on your own full suspension bike any lateral movement of the
    disc when seated on the bike?

    Thank!

    Christophe

    Message 1 in thread From: Caspar Lugtmeier & Eva Skotarczak ([email protected]) Subject:
    Frame/wheel flex and disc brake problem

    View this article only Newsgroups: alt.mountain-bike Date: 2003-11-10 03:04:05 PST

    Hello,

    I have some problems with my rear disc brake: When the rear is not weighted, the wheel+rotor spins
    freely and the distance between pads and rotor is evenly ditributed. However, when I sit on my bike
    it touches the inside pad (note that I weigh 68 kg....).

    At first it was driving me crazy (re-adjusting the caliper+pads numerous times), but now I have
    identified the problem, and am very close to finding the cause:
    1) frame flex (Specialized Stumpjumper FSR comp 2003)
    2) wheel flex (Shimano deore disc+Mavic X221 rims, not so good anyway, looking for upgrade with DT
    swiss component wheels)
    3) skewer flex? (Shimano deore, already ordered XTR skewers)

    Note that the distance the rotor moves (when you put weight on the bike) is very small (+/- 0.2 mm)
    but deadly when using discs. I hope the cause can be found in 2) and 3) (will try with some other
    wheels at the LBS) but I am afraid that it might be cause nr 1) When the rear wheel is weighted it
    should bend in a way that the rotor touches the outer pad (if that was the cause) right?

    Anyway, have some of you experienced similar problems?

    Thanks, Caspar

    (PS: now I have the pads adjusted so that they are free when I sit on the bike.... and drag when you
    just spin the wheel)
     
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  2. Hello Christophe,

    I have visited my LBS and verified that the problem is in the FSR frame (or bearings) The problem
    did not occur with a different rear wheel (Shimano XT tubeless set), so it must the frame/bearings.
    They will contact Specialized to see what they think about this.

    Caspar

    [email protected] (christophe) wrote in message
    news:<[email protected]>...
    > Hi all,
    >
    > This is the first time I post here, I'm Christophe 27 year old, riding a 03 Specialized FSR disc
    > in the french alps.
    >
    > I post this e-mail cos I'm experiencing exactly the same trouble as yours with exactly the same
    > bike and component setup.
    >
    > My dealer already exchanged the frame and wheel, and got the deore disc brake checked by shimano
    > (no issue there). I can reproduce the issue on my wife's FSR also, with my wheel and brake
    > mounted on it.
    >
    > I currently do no what to do anymore, because this looks like a "built-in feature" of the
    > stumpjumper FSR to have that kind of flex.
    >
    > Did you manage to fix this by changing a skewer or getting a better hub than the deore disc?
    >
    > Question for all, do you experience on your own full suspension bike any lateral movement of the
    > disc when seated on the bike?
    >
    > Thank!
    >
    > Christophe
    >
    >
    >
    > Message 1 in thread From: Caspar Lugtmeier & Eva Skotarczak ([email protected]) Subject:
    > Frame/wheel flex and disc brake problem
    >
    >
    > View this article only Newsgroups: alt.mountain-bike Date: 2003-11-10 03:04:05 PST
    >
    >
    > Hello,
    >
    > I have some problems with my rear disc brake: When the rear is not weighted, the wheel+rotor spins
    > freely and the distance between pads and rotor is evenly ditributed. However, when I sit on my
    > bike it touches the inside pad (note that I weigh 68 kg....).
    >
    > At first it was driving me crazy (re-adjusting the caliper+pads numerous times), but now I have
    > identified the problem, and am very close to finding the cause:
    > 1) frame flex (Specialized Stumpjumper FSR comp 2003)
    > 2) wheel flex (Shimano deore disc+Mavic X221 rims, not so good anyway, looking for upgrade with DT
    > swiss component wheels)
    > 3) skewer flex? (Shimano deore, already ordered XTR skewers)
    >
    > Note that the distance the rotor moves (when you put weight on the bike) is very small (+/-
    > 0.2 mm) but deadly when using discs. I hope the cause can be found in 2) and 3) (will try with
    > some other wheels at the LBS) but I am afraid that it might be cause nr 1) When the rear wheel
    > is weighted it should bend in a way that the rotor touches the outer pad (if that was the
    > cause) right?
    >
    > Anyway, have some of you experienced similar problems?
    >
    > Thanks, Caspar
    >
    > (PS: now I have the pads adjusted so that they are free when I sit on the bike.... and drag when
    > you just spin the wheel)
     
  3. In article <[email protected]>, [email protected] says...
    > Hello Christophe,
    >
    > I have visited my LBS and verified that the problem is in the FSR frame (or bearings) The problem
    > did not occur with a different rear wheel (Shimano XT tubeless set), so it must the
    > frame/bearings. They will contact Specialized to see what they think about this.
    >
    > Caspar
    >

    Did you mean to say this problem DID occur with a different rear wheel?

    That's kind of a barometer on FSR bikes to tell you when your shock bushing or linkage beargins are
    geting worn. Although it also happens with a flex or loose hub. The eyelet bushing on the bottom of
    the shock wears out first, the 688 bearings on all the small pivots got next and the big 608 bearing
    behind the BB go last (or never). I get about half a season out of the shock bushing and a year out
    of the 688 bearings, ysually it's only the top ones that really need replacing but I do them all.
    I've never had to replace the main pivot bearing on one of my own bikes.
    --
    _________________________
    Chris Phillipo - Cape Breton, Nova Scotia http://www.ramsays-online.com
     
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