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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 09-02-05, 01:04 AM   #1
Q23
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chain irregularities?

So I was working on my bike and noticed how tight it was on part of the stroke. It when from 1/2 of play to, very tight. Spinning the cranks by hand, I noticed the tighting and loosening throught the stoke. It didn't feel smooth at all. So I studied how the chain (low end sliver Izumi) was sitting on the chain ring (a really nice 42t TA) and saw it sat lower in the teeth at a certain point on the ring (where it was loose in the stroke).

I visually marked where that piont was on the ring and removed then rotated the chain so it engaged at a different spot than before. The loose/ tight part move with the chain. With some work I got it to feel much smoother.

I would take this to mean my chain is slightly irregular. I would challenge ya'll to experiment doing the same and see if cheap chain are more prone to this. I'll be looking at a new chain soon to see a difference as well. I need a half link right now so the Shadow Conspiracy would be nice for the symmetrical look, but a NJS might be a better choice for quality.
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Old 09-02-05, 07:40 AM   #2
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How long have you had the chain? The irregularities in it may just be uneven wear. I would also try to center your chainring, using SB's method, to see if you can get uniform tension.
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Old 09-02-05, 07:57 AM   #3
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What this means is that your chainring is not round, or it is mounted off-center. You can loosen the chainring bolts slightly and tap on the chain to center it. If you have a cheaper chainring it is probably slightly oval, which should not make a big difference while riding but will definitly be noticable to the eye.
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Old 09-02-05, 11:06 AM   #4
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it's a new chain with new ring that has been centered. I tossed the first used ring I hade because it was so uneven.
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Old 09-02-05, 12:38 PM   #5
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One thing to keep an eye out for is irregularly drilled cogs. My friend had an EAI one that was threaded slightly off-center. It produced the exact same type of tight/loose pattern that you describe.
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Old 09-02-05, 12:52 PM   #6
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Quote:
Originally Posted by biff
One thing to keep an eye out for is irregularly drilled cogs. My friend had an EAI one that was threaded slightly off-center. It produced the exact same type of tight/loose pattern that you describe.
I was about to say that. I saw a Soma cog that was threaded the say way.
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Old 09-02-05, 03:54 PM   #7
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again...ring is new and one of the best I've seen and is true and centered. The chain tensioned on one part of the ring. I removed and rotated the chain, and it tensioned on a diffferent part of the ring.
The cog was a new duraAce. I'll have to check that as well I guess.
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