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  1. #1
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    Rear Derailleur Index shift adjustment help, please?

    I've got Shimano SL 750 9 speed shifter. I don't think these are rapid rise shifters. The shifting is off. Please tell me how to correct it.
    The bike is on a bike repair stand.

    The symptom(s):
    When downshifted to the 3rd smallest sprocket, the chain shifts to the 2nd smallest sprocket without any additional shift on the shift lever. This occurs when the chain is on the small or large front chain ring (the middle ring was not tested).
    After up shifting to the largest rear sprocket, there is still one more available shift/click in the shifter (is this a trim shift/click). The up shifts are fine otherwise.

    Sheldon Browns site on adjusting index shifters has got me this far, but now I'm stumped. I've tried making fine adjustments in the RD cable tension adjuster, but that does not seem to solve this problem. It only causes the chain to shift or not shift.
    Thanks For Your Help,
    Uni

  2. #2
    Fat-tired Roadie
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    Count your down shifts (those to the larger cogs) really carefully - are you skipping a cog at some point? There shouldn't be a 9th click on 9-speed shifters. Even if the shifter had it, you shouldn't be able to get to it because of the limit on the derailleur.

    There are some "usual suspects" for bad rear shifting. Dirty cables, dirty drivetrain, worn out cables and housings, misaligned rear derailleur hanger, dirt packed in the derailleur. I'd start by cleaning up the rear derailleur itself and the spot under the bottom bracket if your cable has that kind of routing. I'd also give the housings a feel. There's a trick - put the bike in one of the large cogs, then shift several times to release tension, but without pedaling. Now you can take the housing off and try sliding it up and down the cable. It should feel smooth. The problem you're having sounds to me like a sticky cable problem - the spring on the derailleur is not quite strong enough to keep the derailleur moving against the friction from dirt along the cable run.

    How old is your drivetrain?
    "Don't buy upgrades; ride up grades." -Eddy Merckx

  3. #3
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    As Andrw noted, check the cables and housing, and the bb guide if you have one. Also have the derailleur hanger alignment checked. Those are the two most common causes of shifting problems. The SL M-750 shifters don't have a "trim" feature, so something is definitely off here. It almost sounds as if you were one click off when you attached the cable to the derailleur. Anyway check the cables and the hanger to start with.

    Good Dirt
    "I do whatever my Rice Cripsies tell me to!"

  4. #4
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    Quote Originally Posted by Unicornz0 View Post
    After up shifting to the largest rear sprocket, there is still one more available shift/click in the shifter
    Yeah, the indexing is off by one sprocket.

    http://www.parktool.com/blog/repair-...nts-derailleur
    Last edited by rlouder; 07-08-2011 at 09:14 AM.

  5. #5
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    Quote Originally Posted by Unicornz0 View Post
    After up shifting to the largest rear sprocket, there is still one more available shift/click in the shifter (is this a trim shift/click). The up shifts are fine otherwise.

    Cable needs to be looser...If that doesn't fix it then see above.

  6. #6
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    Thanks everyone.
    AndrwSwitch is right. For anyone having this or a similar problem look here for a step by step fix:


    http://www.bikeforums.net/showthread...0#post12898000

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