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Singlespeed & Fixed Gear "I still feel that variable gears are only for people over forty-five. Isn't it better to triumph by the strength of your muscles than by the artifice of a derailer? We are getting soft...As for me, give me a fixed gear!"-- Henri Desgrange (31 January 1865 - 16 August 1940)

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Old 11-30-09, 09:08 PM   #1
erpdat
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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
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Old 11-30-09, 09:12 PM   #2
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Almost all fixed gears will do this. Extremely high quality parts/frames will mitigate this effect somewhat.
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Old 11-30-09, 09:16 PM   #3
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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.
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Old 11-30-09, 09:16 PM   #4
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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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Old 11-30-09, 09:43 PM   #5
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http://sheldonbrown.com/fixed-conversion.html#tension
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Old 11-30-09, 09:49 PM   #6
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hmmm Half inch of slack is a bit scarry...u sure its a track chainring?
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Old 12-01-09, 02:54 AM   #7
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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.
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Old 12-01-09, 04:50 AM   #8
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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.
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Old 12-01-09, 07:16 AM   #9
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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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Old 12-01-09, 10:13 AM   #10
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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...
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Old 12-01-09, 12:20 PM   #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.
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Old 12-01-09, 12:45 PM   #12
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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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