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  1. #1
    LWP
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    Chain skipping on one cog.

    First the checklist:

    - new wheels, cassette, chain and cables
    - hanger alignment checked using Park DAG-2
    - cassette is assembled correctly, including rear spacer, and properly torqued
    - cable is connected to derailleur properly
    - chain length is correct, no kinks, bends or tight links

    Now to the problem. It won't run on the next-to-largest rear cog. It's shifting like brand-new through all of the gears except when it gets to that one. Then it skips and grinds for a 1/2 second and jumps to the largest cog. Messing with the barrel adjuster just makes things start going bad in the middle area of the cassette but doesn't fix the problem. It runs great on the cogs on either side of that one (and all the others), just not on that one.

    I tried putting the old cassette back on and it did the same thing (despite the fact that it wasn't doing it before). So I'm assuming the problem is somewhere else. To save someone having to say it, I don't have a LBS. I live in a small, remote town in northwest Ontario, Canada. The closest bike shops are 5 hours or more away. It's not impossible to go to one but it involves taking 2 days off work so life is a lot better when I can do this stuff myself... but this one has me stuck. In case it matters, Shimano hub, Ultegra 6600 triple drivetrain, 12 - 25 cassette.
    Crusty old farts are people too.
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  2. #2
    'brifter' is a lame word.
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    I read your post 3-4 times and still can't think of anything...it sounds like you've been pretty thorough and judging from how you've written this it sounds like you know what you're doing. I'll run it through my head a few more times and then run it by the guys at work tomorrow and see if they can come up w/ anything.
    The shifter feel normal? Does it ever 'miss' a shift and just move w/o catching the next gear?
    i work for some bike racers...
    2013 Trek Madone 5.9 w/ '12 SRAM Red
    2010 Cervelo T1 sprint bike
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    oh, those belong in another forum

  3. #3
    Roadbike Rider
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    Check cable routing for kinks and damaged housing ends. Check inner cable flow through the housing and through the cable guide under your bottom bracket. It should glide freely
    "It's supposed to be automatic, but actually you have to push this button. "
    John Brunner (Stand on Zanzibar)

  4. #4
    wim
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    Not being able to see this, I can only offer a general observation. One of the defining symptoms of tolerance buildup is a function that operates as it should at the beginnig of a cycle or a phase, but stops working properly when the function progresses towards the end of that phase or cycle because of tolerance buildup.

    If, for example, the cable is just a tiny bit too tight with the derailleur resting on the on its high gear limit screw, it might take those 8 shifts before that error gets large enough to manifest itself on the 9th cog. It would also manifest itself on the 10th cog, but can't because of a properly adjusted low gear limit screw.

    But as said, pure theorizing.

  5. #5
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    Quote Originally Posted by wim View Post
    Not being able to see this, I can only offer a general observation. One of the defining symptoms of tolerance buildup is a function that operates as it should at the beginnig of a cycle or a phase, but stops working properly when the function progresses towards the end of that phase or cycle because of tolerance buildup.

    If, for example, the cable is just a tiny bit too tight with the derailleur resting on the on its high gear limit screw, it might take those 8 shifts before that error gets large enough to manifest itself on the 9th cog. It would also manifest itself on the 10th cog, but can't because of a properly adjusted low gear limit screw.

    But as said, pure theorizing.
    Not following your logic. If the cable is 1 mm too short in cog 1, it is still 1mm too short on cog 10. There is no error that is accumulating.

    Now, if the cable drum in the shifter was a bit too large, then cable would get progressively shorter as you went from cog 1 to cog 10. But I don't think that's what's going on here, do you?
    ... 'cuz that's how I roll.

  6. #6
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    I'd start again with the final setup. ie Cable off, limits checked, then attach cable with a little tension, making sure shifter is fully upshifted.

    I'm suspecting 8 shifts instead of 9.
    There's sometimes a buggy.
    How many drivers does a buggy have?

    One.

    So let's just say I'm drivin' this buggy...
    and if you fix your attitude you can ride along with me.

    http://www.youtube.com/watch?v=GekiIMh4ZkM

  7. #7
    wim
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    Quote Originally Posted by looigi View Post
    Now, if the cable drum in the shifter was a bit too large, then cable would get progressively shorter as you went from cog 1 to cog 10. But I don't think that's what's going on here, do you?
    No, I certainly don't. But I'm woefully ignorant of the internal workings of an STI shifter and can imagine all sorts of tolerance buildups in there other than an out-of-tolerance drum.

    Pursuing another thought: Don't STI shifters overshift very slightly on each click, then let the derailleur come back a tad as the lever returns?
    Last edited by wim; 08-03-2013 at 04:46 AM.

  8. #8
    A wheelist
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    Quote Originally Posted by bikerjulio View Post
    I'd start again with the final setup. ie Cable off, limits checked. Then attach cable with a little tension, [B]making sure shifter is fully upshifted.
    That's what I'd do. Go back to basics. Cable off & make sure the derailer shifts cleanly into the small cog just using the thumb and the spring. Make doubly sure that the shifter lever is fully upshifted before re-connecting. Then setup cable tension to the n'th degree and finally set up the indexing (to the same n'th degree). If that didn't fix it I'd be swapping shifters - easier said than done of course.
    .
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    I'm not cranky; I just have a violent reaction to stupid people.

  9. #9
    LWP
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    Thanks everybody. I'll go through the suggestions and see what happens. Despite the appearance my first post may give, I really don't know a lot. I had help with suggestions from others in getting as far as I have. I'm just beginning to get into trying to do my own work. I had a local guy that used to work in a bike shop in a busy city a few hours from here that was doing all of my work... but he moved back to the city. So I'm out of excuses to not learn.
    Crusty old farts are people too.
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  10. #10
    LWP
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    So I started from zero once again as suggested and I realize what the problem was now. I think I was being too delicate with pulling the cable taught before attaching to the derailleur. I was getting the line through the pinch bolt right and being careful not to pull the derailleur forward and not even noticing that the cable was pretty floppy at the downtube. Apparently I was able to get enough adjustment with the barrel adjuster to get it to function but not to function properly. This time I used one hand to pull the cable taught at the downtube until it felt right there then pulled out the slack at the derailleur with the other hand and tightened the bolt. It's now shifting through all of the gears and staying on the cogs. It's shifting from largest to smallest perfectly, still not quite as smooth as it should be when going from smallest to biggest but no jumping gears so probably just need to tweak the adjuster a bit more. I'm feeling really dumb right now but I need to learn this stuff... so thanks for the help.

    Edit: I really didn't want to come back and admit what the problem turned out to be, I'm feeling incredibly stupid, but with everybody trying to help it didn't seem right to leave it hanging. Thanks everybody.
    Last edited by LWP; 08-03-2013 at 02:05 PM.
    Crusty old farts are people too.
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  11. #11
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    I honestly doubt that any of us will be able to come up with the answer if cxwrench is stumped, but the only other thing I can think of other than the above is re-double-check the setting of the limit screws. Basically, I believe, the shifter just divides the distance between the end derailleur settings into 9, 10 or 11 equal increments. If either end (or both by a little) are just a tad out, it could possibly cause your problem (at least that seems to have fixed the issue when I've had this problem once or twice - and after doing all the other stuff you've done). The normal answer is that you have one cog that's worn more than the others (possible for a variety of reasons), but you seem to have eliminated that possibility. Good luck and let us know the solution if you find one.
    "Five and Dime, all the time!"

  12. #12
    A wheelist
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    Quote Originally Posted by LWP View Post
    So I started from zero once again as suggested and I realize what the problem was now. I think I was being too delicate with pulling the cable taught before attaching to the derailleur. I was getting the line through the pinch bolt right and being careful not to pull the derailleur forward and not even noticing that the cable was pretty floppy at the downtube. Apparently I was able to get enough adjustment with the barrel adjuster to get it to function but not to function properly. This time I used one hand to pull the cable taught at the downtube until it felt right there then pulled out the slack at the derailleur with the other hand and tightened the bolt. It's now shifting through all of the gears and staying on the cogs. It's shifting from largest to smallest perfectly, still not quite as smooth as it should be when going from smallest to biggest but no jumping gears so probably just need to tweak the adjuster a bit more. I'm feeling really dumb right now but I need to learn this stuff... so thanks for the help.

    Edit: I really didn't want to come back and admit what the problem turned out to be, I'm feeling incredibly stupid, but with everybody trying to help it didn't seem right to leave it hanging. Thanks everybody.
    There is absolutely NO need to feel dumb LWP. I think I can speak for everyone here that we have ALL had duhhh moments in our bike fixing careers - and I'm sure we all still have them even though some of have been fixing bikes for decades - not just weeks, months or years.

    Try this in your quest for perfect indexing - click up or down one gear without turning the cranks. Then, with the gentlest of crank rotations, see if the shift happens. If it doesn't, give the barrel adjuster a tweak (in the right direction) and try again. Go up & down all the gears using this pre-selector move. The indexing needs to be dead on.
    .
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    I'm not cranky; I just have a violent reaction to stupid people.

  13. #13
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    Did you check chain orientation? Some chains have a specific inside/outside orientation. It can cause crap shifts

  14. #14
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    Quote Originally Posted by Tupelo View Post
    Did you check chain orientation? Some chains have a specific inside/outside orientation. It can cause crap shifts
    Did you read his post (several hours before yours) where he figured it out?

  15. #15
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    Quote Originally Posted by Kerry Irons View Post
    Did you read his post (several hours before yours) where he figured it out?
    and failed to thank me
    There's sometimes a buggy.
    How many drivers does a buggy have?

    One.

    So let's just say I'm drivin' this buggy...
    and if you fix your attitude you can ride along with me.

    http://www.youtube.com/watch?v=GekiIMh4ZkM

  16. #16
    LWP
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    Quote Originally Posted by bikerjulio View Post
    and failed to thank me
    Apologies. I did say "thanks for the help"... but I have no problem at all saying it again. Thank you for your help bikerjulio. Went for a ride yesterday and it was like riding a new bike again. I appreciate it.
    Crusty old farts are people too.
    - 10ae1203

  17. #17
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    Thanks Kerry Irons for your very tactful reply. It is much appreciated. I will endeavor to be more thorough in my reading of all posts because of your response. Thanking you!

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