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Thread: chain skipping

  1. #1
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    chain skipping

    After assembling my first singlespeed (from used stuff) I rode it around the yard and immediately the drivetrain seems to "skip" or "miss" when under load. When pedalling it feels like it lunges forward for an instant and then catches again. As long as there is no load it seems to work fine, but once under load it happens often.

    I can't quite figure what the problem is, but it feels like it's the chainring. It only happens when under load. The guys in "Tooltime" said it might be the old chainring that's sharktoothed (although it looks ok to me) and the chain is slipping off the worn teeth. They also said I should be asking here.

    The set up goes like this. New 8-speed chain, new rear cog (16t) with spacers, new Singleator, old 8-speed chainring (32t), old GT backwoods frame, etc.

    Any advice is greatly appreciated. In the meantime I've already ordered a new ss chainring so the drivetrain will be "all new".
    Thanks.
    Dennis

  2. #2
    Steamroller
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    Chainline straight ....... width of cog?

    Quote Originally Posted by dyurcik
    After assembling my first singlespeed (from used stuff) I rode it around the yard and immediately the drivetrain seems to "skip" or "miss" when under load. When pedalling it feels like it lunges forward for an instant and then catches again. As long as there is no load it seems to work fine, but once under load it happens often.

    I can't quite figure what the problem is, but it feels like it's the chainring. It only happens when under load. The guys in "Tooltime" said it might be the old chainring that's sharktoothed (although it looks ok to me) and the chain is slipping off the worn teeth. They also said I should be asking here.

    The set up goes like this. New 8-speed chain, new rear cog (16t) with spacers, new Singleator, old 8-speed chainring (32t), old GT backwoods frame, etc.

    Any advice is greatly appreciated. In the meantime I've already ordered a new ss chainring so the drivetrain will be "all new".
    Thanks.
    Dennis
    Is your chainline straight? your stock ring is likely ramped, pinned, has short teeth or all of these to aid shifting, even if it's in good shape you can have problems if your chainline is not right on.

    Another thought, are you certain that your new SS cog is 3/32 and not 1/8 wide? I got a new novatech cheapy steel rear cog recently and was inadvertantly given one that was 1/8" wide, causing the chain not to seat down into the notches, if it did seat it would stick there. I figured it out pretty quickly and solved it by putting on a 1/8" PC-1 chain I had around.
    Two Wheeled and Too Big

  3. #3
    Sofa King We Todd Did
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    When you installed the chain, did you take off links and/or put links back on the chain? A tight link can cause chain to jump.

  4. #4
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    Caution;  Merge;  Workers Ahead! Yep

    My bet goes toward a Shimano DX cog or similar (1/8th") that will NOT mate with the 8 speed (3/32") chain!

    The "BMX" cogs are almost always 1/8th inch, TTBOMK. You'll need a PC-1 or PC7-X (my favorite!) or similiar one eighths inch chain.

    Please DO check your chainline too!

  5. #5
    Retro Grouch
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    I say it's your Singleator..

    Quote Originally Posted by xrmattaz
    My bet goes toward a Shimano DX cog or similar (1/8th") that will NOT mate with the 8 speed (3/32") chain!

    The "BMX" cogs are almost always 1/8th inch, TTBOMK. You'll need a PC-1 or PC7-X (my favorite!) or similiar one eighths inch chain.

    Please DO check your chainline too!
    First Shimano DX cogs only come in 3/32" (Shimano freewheels come in 3/32, 1/8 and even 3/16), so it's doubtful its the cog or 8 speed (3/32") chain. Chainline? Yes that can cause problems; but usually with derailment, not skipping. The usual suspect in skipping under load is caused by the the chain riding up on the rear cog teeth and then slipping to the next teeth. With a Singleator (or other spring loaded tentioners) it's a problem with chain wrap. There are two remedies; use a bigger cog or use the singleator in the push up mode. The later is the easiest and works the best. I also strongly recommend afer switching the the push up mode you use a zip tie to hold the Singleator in place; first this will stop any chain slap and second it will stop skipping on bumpy climbs. Another way to minimize the problem is use a 3/32" half link to reduce the chain slack. As one poster so succinctly pointed out 1/2" of extra chain equals 2 " of chain slack.

    The truth is, while tensioners look cool, they don't work near as well as derailleurs. But, of course bling is part of SS, so you pay your money and take your choice.

    1G1G, Brad

  6. #6
    Cold. Blue. Steel.
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    2ยข = new chain and new cog merits a new chainring, too. IMO. Chainline is of the essence and having your chain, cog and ring be of the same width is vital, as mentioned already.

    OGG
    Spinning and Grinning...

  7. #7
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    lots of stuff to try

    Apparently I have a lot to check out.

    I do think that my chainline is pretty good, but how "perfect" does the chainline have to be? Geared bikes work just fine with multiple gear combos that result in chainlines of all different angles (not that straight isn't ideal), right? Just wondering. I'm still the green one here. Also, I did remove links, but I was careful to check for any stiff links.

    I suspect the 1/8(?) cog and the 3/32 chain might be the problem. The Singleator theory seems highly possible too. Thanks for the tip on the "half-link", that would probably help a lot with the copious slack.

    I'll post my findings after I mess around with the SS a bit.
    Thanks for all the great advice.
    Dennis

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