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  1. #1
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    Bonking ... not feelin' well Help! 04 Scalpel rear end auto shifting problem

    I've had problems for a long time with my 04 Scalpel 800 "auto-shifting" when riding over flat but bumpy trails, particularly when on the biggest three rear cogs. Pretty much when I'm riding fast it will on its own start jumping up then down two to three gears. If I'm riding on flat surfaces it never occurs, shifts perfectly.

    I've replaced all the drivetrain components and am now running XTR front crankset, XTR 9 speed chain, XTR long cage Der, XT front Der, XT cassette, problem continues.

    My thoughts are it may be related to the carbon chainstays. It always happens when they are heavily flexing, I think when they flex it is moving the rear end enough to shift. I weigh 180 Lbs, wonder if my heavy weight on my medium frame is an issue or if the chainstays are messed up.

    Has anybody else had similar issue or can recommend a fix?

    Thanks
    Rich

  2. #2
    NEPMCPMBA President
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    I have a medium old-skool scalpel, and I'm 180. No problems.

    However, I HAVE had these problems in the past. The first time, it was due to a dirty cassette. Make sure theres no mud or twigs/junk in the spaces between the gears. Second problem (and this one is embarassing) was that my rear quick release wasn't tight. Oops. Make sure it's tight.

  3. #3
    Sweater
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    Have you checked the tension on the chain?

  4. #4
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    interesting question about checking the tension. I have been using the same chain length from when I bought the bike, this might be something. How would I know if the tension is good?

  5. #5
    Sweater
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    Quote Originally Posted by qsplit
    interesting question about checking the tension. I have been using the same chain length from when I bought the bike, this might be something. How would I know if the tension is good?
    There should be a tension adjustment screw on the derailleur near the hanger.

  6. #6
    LA CHÈVRE
    Reputation: Dan Gerous's Avatar
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    A friend of mine had many shifting problems on his Scalpel, it was just the rear derailleur cable and housing. Dirty cables and housings are a doom for shifting...
    Last edited by Dan Gerous; 04-28-2008 at 07:40 AM.

    DAN.GEROUS.NET : MOUNTAIN BIKING : CYCLOCROSS : ROAD :

  7. #7
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    Sometimes it helps to use a bike stand to tune! LOL!
    What do I know, ask the "experts"!

  8. #8
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    Mission complete, thanks for all the help (except the unwelcome sarcasm/mockery from ozvena of course). I tightened the "B" tension screw alittle, went for a ride, it was better. During the ride I tightened it some more and the problem is gone. Two rides now, good to go.

  9. #9
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    My advise was well intended. I don't expect every bike owner to also use a bike stand. Sometimes you think you are doing it correctly or you even think the problems is gone but you may found out that you were not so correct once you put it on a bike stand.

    "auto shifting problem" most of the time means that you did something incorrectly. Also you mentioned that you have the problem for a long time and went through an expense of XTR parts. I though I would recommend you a tool instead of your path of replacing parts to fix your issue.
    What do I know, ask the "experts"!

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