Shifting causes chain to fall off

Discussion in 'Cycling Equipment' started by vshin, May 18, 2004.

  1. vshin

    vshin New Member

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    I have a full Shimano Ultegra system but I've been running into a problem with shifting the front derailleur. Specifically, I try to shift from the small to large ring and it requires two "clicks" to do so. The biggest problem is that sometimes I can shift the chain right past the large ring and have it fall off. I almost got into several crashes from this problem and I haven't been able to fix it. I've been making adjustments according to the instructions that came with the bike but nothing seems to work.

    I have a Scattante CFR 2003 double. Pretty new and the front derailleur isn't bent or broken as far as I can tell.

    Sorry if this is a common question, but I've tried searching the forums for an answer without success. Maybe I haven't been using the right keywords.
     
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  2. boudreaux

    boudreaux New Member

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    The first click is probably the trim position for the small ring,unless your cable tension is way too loose. www,parktool.com has the drill on derailer adjustment in the repair section. Start at the BEGINNING. Overshifting the bit ring is due to a too loose hi limit adjustment. Doing it yoursefl is good,If you know what you are doing and can follow instructions.Otherwise a Good LBS can save lots of grief.
     
  3. mjw_byrne

    mjw_byrne New Member

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    The front derailleur has two limit screws on it. One of them determines how far out the derailleur can extend. You need to adjust this screw so that the derailleur cannot go far enough to throw the chain off the ring. That ought to do the trick. If you can't figure it out, a bike shop should be able to do it in about 30 seconds, and they'd have to be REALLY tight not to do it for free.
     
  4. lokstah

    lokstah New Member

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    And let you watch, at that... probably a good idea. Good luck; it's not a big problem. The limit screws generally need only one good adjustment.

    Chances are the thing was in a dopey place when you got it.
     
  5. boudreaux

    boudreaux New Member

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    Mindless fidling usually just makes it worse.The right way is to check derailer alignment and position and start from the beginning, with a loose cable and the shifter in the granny ring position, and the chain on the small ring and big cog.Only then can the low limit screw be set.There is a methodology to doing it right,rather than just fiddling.
     
  6. vshin

    vshin New Member

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    I would like to thank everyone here for the help. Especially for the link to parktools; I found that very helpful. It turns out the H-screw was loose and that was the the reason why I kept throwing the chain off. I tightened it and now problem solved.

    Thanks again.
     
  7. meehs

    meehs New Member

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    I suspect that all you did by "tightening" the "H" screw is decrease the amount of outward travel of the front derailleur. It must be the high limit adjustment screw you're refering to. It's not a screw that needs to be "tightened", it's an adjustment screw. Be careful because if you tighten it too much you won't be able to shift into your big ring at all. But hey, whatever works...
     
  8. boudreaux

    boudreaux New Member

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    Yeah, it sure is the Hi limit. But, how do you think you make an 'adjustment' using a a screw that is doing nothing more than acting as a limit or stop ??.. You tighten or loosen it. Easy enough language to understand.
     
  9. lokstah

    lokstah New Member

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    As with any technical tweak, the important thing is to understand what you're actually doing -- going through the motions to get it right leaves you likely to get into trouble down the road. Once you earn an understanding of how an element like limit screws work, you'll be in good shape.

    Do remember that a properly adjusted limit screw rarely, if ever, needs attention in the future. Less experienced cyclists often head straight for the screws when things get mucky -- a surefire way to get things muckier. Once it's set, try to resist the temptation to fiddle with limits if your drivetrain gets spotty later.

    Yours probably left the shop or factory improperly dialed.
     
  10. meehs

    meehs New Member

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    I guess when I think of "tightening" a screw, to me it means to screw it in until it's tight (thus the word tighten). If you did that with your high limit adjustment screw, you wouldn't be able to shift out of the small ring. Easy enough language to understand...
     
  11. cuervo

    cuervo New Member

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  12. boudreaux

    boudreaux New Member

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    I guess it's all in how the brain is wired.Common usage is loosen or tighten the limit screws. The majority get it. 'Adjust the screw' leaves it hanging ,as in "d'oh ok, which way?"
     
  13. meehs

    meehs New Member

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    Yes, and I would offer that I probably have an inordinate number of crossed wires! You're right though, if you were to just say "adjust" the screw, it's open to (mis)interpretation.
     
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