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Thread: chain tension

  1. #1
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    chain tension

    Is it normal for my chain to get looser as my pedals rotate. There's about a half inch of slack half way through the rotation and an inch of slack on the other half. Just curious.. Never had this before.. Thanks

  2. #2
    cab horn
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    Almost all fixed gears will do this. Extremely high quality parts/frames will mitigate this effect somewhat.
    Mes compaingnons cui j'amoie et cui j'aim,... Me di, chanson.

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    The bus, Gus mrvile's Avatar
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    Most chainrings are not completely circular...hence, difference in tension throughout the pedal stroke. High end chainrings are much closer to completely circular than cheaper stuff.

  4. #4
    The bus, Gus mrvile's Avatar
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    Quote Originally Posted by operator View Post
    Almost all fixed gears will do this. Extremely high quality parts/frames will mitigate this effect somewhat.
    Not sure how a frame of any kind would have an effect on this...?

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    Velodrone pckopa's Avatar
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  6. #6
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    hmmm Half inch of slack is a bit scarry...u sure its a track chainring?

  7. #7
    Gentlemen. ADSR's Avatar
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    If it's just when you're pedaling don't worry about it. It's just some flexing in the frame or some such. If it is slack that goes in and out of your chain even with no pressure on the pedals, your chainring is out of round. This you should probably not worry about either unless it is enough to throw your chain during normal operation. Honestly if the chain stays on you should be fine. It may get annoying but it won't kill you.
    The bums will always lose.

  8. #8
    Senior Member Retro Grouch's Avatar
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    Quote Originally Posted by mrvile View Post
    Most chainrings are not completely circular...hence, difference in tension throughout the pedal stroke. High end chainrings are much closer to completely circular than cheaper stuff.
    I don't think it's the chainrings aren't circular so much as that it's hard to get them perfectly concentric on the crank spider.

  9. #9
    Senior Member mihlbach's Avatar
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    Quote Originally Posted by Retro Grouch View Post
    I don't think it's the chainrings aren't circular so much as that it's hard to get them perfectly concentric on the crank spider.
    Its usually a bit of both. However, I have encountered numerous chainrings that are clearly not circular. As long as the chainline is reasonably straight, minor variance in chain slack/tension is not a big deal, although you may find it to be annoying when riding fixed.

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    my first fix had the same simptoms , but it was a road bike chain ring...ever since I rode true track gear never run in to it again...

  11. #11
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    looks like i shoulda dropped the $80 on the sugino messenger ring.. my bike is working but its annoying as hell.

    and yeah, the tension changes even without pressure.

  12. #12
    Senior Member filtersweep's Avatar
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    Quote Originally Posted by Retro Grouch View Post
    I don't think it's the chainrings aren't circular so much as that it's hard to get them perfectly concentric on the crank spider.
    Very true-- and I have never understood why the interface allows for so much wiggle room.

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