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Old 06-06-08, 02:12 PM   #1
Thirstyman
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dropping chain - doomed to do it?

I'd appreciate advice on this persistent problem.

Am I doomed to drop the chain if 3 three conditions are present:

1. chain on inside (largest) 1 or two rear cogs
2. I run my chain tension loose as specified by Sheldon Borwn (large large while skipping derailleur and adding 1 link (3 pins)).
3. panic shift front - shifting the front derailleur from the large chain ring to the small in one complete depressing of the front brifter lever.

I realize that none of the 3 probably help to avoid dropping the chain and I try not to panic shift but sholdn't the proper front derailleur setting eliminate this problem? How much is the problem influenced by chain tension. Also, I find the drive train behaves entirely differently when under load than on the work stand. load introduces more hesitation so this has been challenging to troubleshoot.

I have been periodically dropping my chain off the inside of the small ring -while using the inside (largest) 1 or 2 rear cogs - when shifting from the large to the small chain ring. I have adjusted both the inside and outside positions (for small and large rings) of the front derailleur to be as close as possible without rubbing but the problem persists.

Last edited by Thirstyman; 06-09-08 at 05:39 AM.
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Old 06-06-08, 03:04 PM   #2
HillRider 
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1. That's ok except on the large chainring. It's called cross chaining and is hard on the chain and cogs.

2. That's not "loose", that's the proper way to size a chain.

3. If you are in the largest cog, you shouldn't be in the largest chainring even if the chain length will allow it. See #1.

Despite all of those procedural errors, dropping the chain can be avoided by adding a Third Eye Chain Watcher or N-Gear Jump Stop. These are retaners that fasten to the seat tube inboard of the crank and have a plastic tooth or metal plate that runs a close clearance with the inner chainring. They are set close enough that the chain cannot fit between them and the chainring and they prevent the chain from overshifting.
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Old 06-06-08, 03:25 PM   #3
c_m_shooter
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+1 on the chain watcher. I couldn't for the life of me get my chain to quit dropping off my Cross Check on rough singletrack until I got one. They are cheap insurance even if you don't drop it very often.
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Old 06-06-08, 03:58 PM   #4
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I will second the N-Gear

I have used it 2+ years now and no drops, but the best reason is the owner/designer

when I called him to order, I asked how I can pay, and he said nevermind, I will send it to you and if you like it just send me a check....he even included a prepaid envelope!!!! that made my day to see that kind of service and trust...

plus it's a great product

just my 2 cents

http://www.gvtc.com/~ngear/whatis.html
N-Gear: What Is A Jump Stop?
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Old 06-07-08, 02:50 AM   #5
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+1 N-Gear. I have one on all my bikes. I don't even mess around - when I get a new bike, I put one on before my first ride. Chains have a nasty way of scratching and gouging new bikes.

Make sure you measure the seat tube. They come in different sizes.
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