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Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

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Old 09-28-03, 10:38 AM   #1
TriDevil
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Chain Suck?

On my bike today I noticed the shifting seemed a little jumpy plus the big ring to small ring transition is off a little. When I got home from my group ride this morning I shifted to the small ring and the chain went to the left of it and wrapped around the bottom bracket area. My chain stay close to the bottom bracket is getting torn up, this has happened twice now. Its a new bike so is cable stretch most likely to blame? Or do the upper/lower limits on the derailleur have something to do with it? If I buy a chain stay protector will it go that far? Ive always seen them centered midway along the chain stay? Any help?
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Old 09-28-03, 12:39 PM   #2
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http://www.fagan.co.za/Bikes/Csuck/
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Old 09-28-03, 04:34 PM   #3
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Thats more info than I cared to know about chain sucks!!! hahaha, that website was very helpful but Im still not sure how to solve the problem for a new chainring. The fixes were all for old,worn parts. I keep my chain lubed so any other thoughts on it?
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Old 09-28-03, 04:38 PM   #4
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I do not think you have chain suck. (BTW, that link is great).

Before you do (or buy) anything. Try checking your chain. A poorly lubed chain or stiff link may account for some of the "jumpiness" that you are noticing. If everything checks out and you are still noticing some problems, you can try taking some slack out of the cable at the shifter.

Regardless of the cables, you may want to adjust the Low Gear Limit on the front derailler. This is generally the one closest to the seat tube and marked with an L. You should try tightening this. Do it in small increments (1/4 turns) until the chain stops falling off. If you go too far, you will not be able to shift to your inner chainring. Then you will have to back out. Keep it methodical to help you remember what you have to "undo" if it gets worse.

Finally, you may want to get a bit of touch up paint for your frame.

Hope this helps.

- Jeff
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Old 09-28-03, 06:07 PM   #5
TriDevil
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yeah that does help, thanks, I'll lube up tonight and ride tomorrow, see if that has any effect. Funny thing was I had gone from big to small a couple of times on the group ride and it didnt do anything till I was right in front of the driveway at home! Oh well, I'll try the limit settings, hopefully this wont happen again.
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Old 09-28-03, 09:57 PM   #6
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Wow there's more about chainsuck in that article than is in my head about total bike knowledge.
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Old 09-30-03, 07:49 AM   #7
Don Cook
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The following was copied from Sheldon Browns website:
The low-gear limit stop, stops the derailer from shifting past the smallest chainwheel and throwing the chain onto the bottom bracket shell. If it is too loose, the chain will fall off when you try to downshift to the small chainwheel. If it is too tight, you it will be difficult or impossible to shift down to the low chainweel.
On older front derailers, the low-gear stop is the one closer to the frame. Many newer designs reverse this position for reasons relating to the mechanism used.

The basic adjustment for the low-gear stop is to set it so that the chain just barely clears the inner plate of the cage when the lowest gear (small front, large rear) is selected. This will usually be the best position for double-chainwheel setups, and will permit the use of most or all of the rear sprockets with a minimum of trimming.

For triple chainweels, it will sometimes be necessary to adjust the low-gear stop a bit looser, so that the outer plate of the derailer can travel far enough to knock the chain off of the middle ring.
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Old 09-30-03, 10:24 AM   #8
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Yep, set yer stops right and your chain won't suck.
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Old 09-30-03, 10:39 AM   #9
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You didn't have chainsuck unless the chain was following the chainring up the backside. Sounds like you had a derailleur in poor tune - two very different problems.
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