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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 10-15-06, 04:55 PM   #1
Eureka
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Dropped Chain, What's up?

Old Italian steel frame, done up as a single-speed.
Riding a gradual, long uphill, putting good effort on getting up. All of a sudden, at the top and while out of the saddle, I almost go over the bars. The chain had come off and was hanging around the crank. It easily fit back on and I was on my way. No more problems on the rest of the ride.

I have no idea why this happened. The rear, while a quick release, was firmly in the dropouts and hadn't shifted up. Frame flex? The chain is not old enough to be that stretched out.

Ideas?
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Old 10-15-06, 04:59 PM   #2
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chain was just to slack probably, check your chainring/freewheel for oldness
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Old 10-15-06, 05:02 PM   #3
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How good is your chainline?
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Old 10-15-06, 05:12 PM   #4
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The exact same thing happened to me recently. I still don't quite understand why, but I think it could be some frame flex. You were mashing up a hill, possibly the chain was too loose combined with a little flex from the frame, and possibly the wheel moved a little bit in the dropouts. Scary ****. Chainline could have contributed to this as well. Be thankful this didn't cause you a serious injury.
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Old 10-15-06, 05:15 PM   #5
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I had a slack as hell fuji touring frame that I rode fixed for a couple years. I had a problem with dropping chains (while riding brakeless) so I got really fastidious with checking chain tension. But sure enough if I hit a bump or rode over streetcar tracks at high speed I'd drop the chain and be on a wild survival ride. As far as I can figure it was frame flex. I got a new frame, swapped all the parts over, and problem solved. Long chainstays with a fixed gear are bad news!
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Old 10-15-06, 05:42 PM   #6
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If the chain "easily fit back on," it was probably too loose to begin with.
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Old 10-15-06, 06:07 PM   #7
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i'm happy that i got a bmx chain. hasn't stretched out as much.

i've seen the damage from a dropped-chain-gone-bad!
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Old 10-15-06, 06:15 PM   #8
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scary brakeless experience
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Old 10-15-06, 06:19 PM   #9
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If you're "mashing" up a hill, you're probably swinging the bike from side to side. If timed just wrong, the chain will swing to the side of the chainring just as the next tooth is moving into contact. Once one tooth is outside the chain, the rest will follow. This is probably exacerbated by the frame flexing. Try to get the chain a little tighter, and make sure your chainline is ok. The further out of line the chainring is, the more likely it is to happen.
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Old 10-15-06, 06:28 PM   #10
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Quote:
Originally Posted by sivat
If you're "mashing" up a hill, you're probably swinging the bike from side to side. If timed just wrong, the chain will swing to the side of the chainring just as the next tooth is moving into contact. Once one tooth is outside the chain, the rest will follow. This is probably exacerbated by the frame flexing. Try to get the chain a little tighter, and make sure your chainline is ok. The further out of line the chainring is, the more likely it is to happen.

+1

Larger frames will flex more in the rear triangle.

Eureka, what size is your frame?
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Old 10-15-06, 07:33 PM   #11
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I see slack chains all the time.
combined with the desire to ride brakeless this is disastrous.

your local shop can teach yhou how to get the tension right.

there should be no "hang" in the chain.

basic tensioners cost a couple of bucks.

the chain ought to be tight enough that you can feel when the chain needs oil because it effects the ride.
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Old 10-15-06, 07:33 PM   #12
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Quote:
Originally Posted by sivat
If you're "mashing" up a hill, you're probably swinging the bike from side to side. If timed just wrong, the chain will swing to the side of the chainring just as the next tooth is moving into contact. Once one tooth is outside the chain, the rest will follow. This is probably exacerbated by the frame flexing. Try to get the chain a little tighter, and make sure your chainline is ok. The further out of line the chainring is, the more likely it is to happen.
I love this forum! After reading all the suggestions and a more detailed review, while chainline looked ok, the chain was slightly slack. Slack enough to take advantage of Sivat's description above. So, a little loose chain and "mashing" (well almost mashing!) and boom.

I moved the wheel back enough to increase the tension and tightened it up real good.

Thanks to all!

BTW: frame is small - 52.
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