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Thread: Chain tension

  1. #1
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    Chain tension

    Hi

    I'm kinda new to the whole singlespeed up-keep and my chain is coming off under load. I don't think anything is needing replaced just yet but I'm wondering what adjustments can be made? I have a chain tensioner, do you move the bolt along as at the moment it is in the middle and it looks like you can undo it to adjust.

    Sorry newbie

  2. #2
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    anyone?

  3. #3
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    got pics of the bike setup?

  4. #4
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    Could be chain tension... or lack thereof. My chain derails frequently whenever I let it get too loose.

    Could also be bad chainline. If the chainring and cog don't occupy the same plane, the chain will constantly be motivated to derail.

    Very hard to discern the latter without actually having the bike in one's possession to study. Photos usually won't cut it.

    Also check for bent teeth on ring & cog &/or twisted/bent sections of chain.

    Finally, don't know what kind of ring & cog you're using, but hopefully they're SS-specific, not pinned/ramped for use with gears. The latter are designed to encourage lateral chain movement.

    --Sparty
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  5. #5
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    To add to what Sparty said, ramped teeth and bad chainline are double trouble. Chainline, chainline, chainline.

    As to tension, as tight as you can get without binding. There is almost always some eccentricity to cogs / chainrings, so spin the drivetrain to see where the tightest spot is and make sure it is not binding at that point.

    It is a trial and error thing for awhile. I find that running the cranks round and round slowly by hand with the bike in the stand, I get a feel for binding.
    "The physician heals, Nature makes well" - real fortune cookie

    CCCMB trail work for trail access - SLO, CA

  6. #6
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    Okay I think what has happened is my chain has stretched slightly so whenever I go over rocky bumpy terrain the chain comes off. Is it just the case with singlespeeds that you need to replace your chain very often compared to geared bikes?

    I don't really want to buy a new chain so my question is can you adjust the chain tensioner or is there no way of doing this? I know in the past the bike shop has said I can either run the chain above or below the rollers as my chain stretched but that's a good inch difference and I think my chain only needs a couple of mm of adjustment to be tight.

    Hope that's clear, I'm loving the singlespeed bike btw.

  7. #7
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    Sounds like you must have vertical dropout frame, if you're running a tensioner. Don't know how you have your tensioner configured: I have better luck with the roller beneath the chain, pushing UP. Also, like the others said, eyeball your chainline. If that's really a straight shot, and you've already tensioned it optimally, I'd be replacing the chainring with a SS specific one, if you haven't already (yay, Surly...I think the best, esp. for the $). As to your question about SS chains, yeah, you do have to replace them a bit more often. Measure. 1/8" stretch in 12", time to replace. But that doesn't sound like the issue here.

  8. #8
    one chain loop
    Reputation: fishcreek's Avatar
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    pictures will help. we need to see your rear hub and how you set up your spacers.
    everything sucks but my vacuum cleaner.

  9. #9
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    Here's a picture of my setup, hope this helps. This picture was taken before the chain stretched.


  10. #10
    one chain loop
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    try to lose a link or two, and have your tensioner pushing up instead of pushing down. i don't think your tensioner is doing its job well with the setup like that. can we see a bumshot like this?

    everything sucks but my vacuum cleaner.

  11. #11
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    sorry I don't have another pic, I'll try and take one later. What do you mean by "pushing up" do I put the chain above it instead of below? Can't I just undo the chain tentioner and move it down more increasing the chain tension?

  12. #12
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    Quote Originally Posted by saga
    sorry I don't have another pic, I'll try and take one later. What do you mean by "pushing up" do I put the chain above it instead of below? Can't I just undo the chain tentioner and move it down more increasing the chain tension?
    yes, remove a few links, a couple of them, and then put the chain on the "up" side of the pulley.

    The bolt that holds the pulley arm, loosen it, move the arm up more until you feel some tension, and you're set.

  13. #13
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    Quote Originally Posted by saga
    sorry I don't have another pic, I'll try and take one later. What do you mean by "pushing up" do I put the chain above it instead of below? Can't I just undo the chain tentioner and move it down more increasing the chain tension?
    When the tensioner pushes up against the chain, it make the chain wrap more teeth on the rear cog, and it is less likely to skip or come off. Pusing down means fewer teeth are wrapped.

    We need a picture from the back to see the cog, chain, and chainring to see the chain line.
    "The physician heals, Nature makes well" - real fortune cookie

    CCCMB trail work for trail access - SLO, CA

  14. #14
    one chain loop
    Reputation: fishcreek's Avatar
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    Quote Originally Posted by saga
    Can't I just undo the chain tentioner and move it down more increasing the chain tension?
    Sorry but we have to get rid of PCS (Parallel Chain Syndrome) and make your bike rideable. just kidding.
    everything sucks but my vacuum cleaner.

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