Fixed gear chain tension modulation
Fred Steele
Posts: 81
Can anyone explain to me why a chain has slight differences in tension throughout the chainwheel's rotation (given that the chainwheel is round and not Bio Pace type, etc). Is this intended, a phenomenon of all fixed gear bikes, or a slight misalignment?
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There's no such thing as a completely circle chainring Fred. Varying tension is completely normal and, as long as the difference is not too pronounced, will be perfectly safe. When setting the chain tension however, always use the point where the chain is at its tightest - not slackest - to avoid chain stretch and sproket wear.All that glitters is probably glass0
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you can try centreing the chain ring, i think sheldon brown describes how to do it.<hr><font>The trick is not MINDING that it hurts.</font>0
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Ok. Thanks.0
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I remember that from my motorbike days, the chain always had a tight spot. As steowen says, the tight spot should be located first and the adjustment done at that point, otherwise the chain will be too tight.0
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better quality rings/cranks/sprockets & chains you get less of a problem...
also tend to use 3/32 rings & sprkts on the road with an 1/8th chain to give you a bit more tolerance of the ring & sprocket being a bit biopace :-(0 -
Prime numbers help here! Or at least co-prime numbers,
Pick a chainwheel which has a prime number of teeth or a sprocket which has a prime number of teeth and the tightspot will occur less frequently. Make sure that the sprocket and chainwheel are not a multiple of each other though.
Eg 48x12 bad (multiple of each other)
53x13 good (both prime)
52x13 bad (one prime but the other a multiple of the the prime.)
45x17 good (co-prime to each other.)0
