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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 11-24-11, 11:01 PM   #1
cocchiarell
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drive train trouble

Hey all. I've been having issues with my drive train when I skid or apply back pressure. My chain skips of my chain ring which leads to a series of events where it locks up the back wheel since it tightens around bottom bracket shell (like a moving rotafix).

I have no idea why its doing this. I've already addressed the following issues and none seem to be the problem:

My chainline is bang on.
My chain tension is good.
My chainring is pretty close to centre.

Could it be that I'm running a 3/32 chain ring with a 1/8 cog and chain? Is it that my cog is stampedI have a steel frame so is it possible that im torquing the BB area of the bike enough to put the chain line off?

Let me know if there is anything I'm over looking.
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Old 11-24-11, 11:27 PM   #2
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You should not run 3/32 chain with 1/8 cog and chainring. 3/32 chain is too narrow so the 1/8 teeth won't go through the links. Change the chain to 1/8.
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Old 11-24-11, 11:29 PM   #3
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He said he's running a 3/32" chainring, with a 1/8" chain and 1/8" cog. He shouldn't be having a problem with this setup.
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Old 11-25-11, 12:00 AM   #4
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another note. it doesnt happen all the time just on a few occasions but enough for me to question the reliability.
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Old 11-25-11, 12:04 AM   #5
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I don't have enough experience to offer any helpful suggestions, I just know that plenty of people run 3/32 chainrings or cogs with 1/8" stuff without issue.
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Old 11-25-11, 12:06 AM   #6
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I've seen this problem happen when there's a stiff or damaged link in the chain - or even a damaged tooth on the chainring or cog - but the chain has to be pretty loose to actually jump off.
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Old 11-25-11, 12:07 AM   #7
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I don't have enough experience to offer any helpful suggestions, I just know that plenty of people run 3/32 chainrings or cogs with 1/8" stuff without issue.
Ya i didnt think it was a problem either
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Old 11-25-11, 12:19 AM   #8
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I've seen this problem happen when there's a stiff or damaged link in the chain - or even a damaged tooth on the chainring or cog - but the chain has to be pretty loose to actually jump off.
upon closer inspection of the chain there was a bit of stiffness near the 1/2 link i installed and one really wonky looking link at a different point in the chain. i'll address these issues and see if it helps. thanks for the input.
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Old 11-25-11, 12:50 AM   #9
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The chainring is for a singlespeed, right? Meaning, there are no ramps or pins on it that would facilitate the chain easily slipping off.
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Old 11-25-11, 01:02 AM   #10
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The chainring is for a singlespeed, right? Meaning, there are no ramps or pins on it that would facilitate the chain easily slipping off.
i'm using a chainring from a double crank but there are no pins or ramps on it (i'm using the smaller chain ring).
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Old 11-25-11, 01:51 AM   #11
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Road rings often have shorter teeth overall, compared to a SS ring, and some have 4-6 teeth that are even shorter than the rest. This can enhance derailability.

Sure seems like there's something else going on here as well. dunno what it could be.
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Old 11-26-11, 02:29 AM   #12
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Close-up pics would help but till then, pretty much ditto to what's been said.
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Old 11-26-11, 02:31 PM   #13
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I have a steel frame so is it possible that im torquing the BB area of the bike enough to put the chain line off?
Lol at that. No you are not torquing your frame that much unless you are literally a bull, rhino, or silverback gorilla. Even then the frame would break before it could flex that much.

Sometimes the best way to find the problem in this situation is to borrow things from friends. Borrow a chain and see if you can jump the chain. If it still jump, borrow a chain ring. If it still jumps, borrow a cog. One of those parts has to be he problem.
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Old 11-27-11, 05:38 PM   #14
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I'm gonna echo what Scrod said about checking for stiff links. Also, chain tension, especially with crappy nuts and bumpy roads can go from good to uh-oh status during even a short ride. Consider chain tensioners?
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Old 12-01-11, 02:29 PM   #15
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Is the chain worn out?
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Old 12-09-11, 06:46 PM   #16
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Throwing this out there... Tighten the lock ring? I donno
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Old 12-09-11, 06:49 PM   #17
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Throwing this out there... Tighten the lock ring? I donno
A loose cog/lockring would have absolutely no effect on chain tension. Zero. Zilch.
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