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Need help with chain snagging on ring bolts when downshifting

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Need help with chain snagging on ring bolts when downshifting

Old 09-18-08, 08:34 AM
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fueledbymetal
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Need help with chain snagging on ring bolts when downshifting

When I shift from the middle ring to the small ring, my chain sometimes snags on the middle ring bolts and my cranks get locked in place. This has only happened while shifting on an incline. It has only started happening recently and the conditions have been dry & dusty. The bolts don't appear to be backed out at all.

When this happens, the chain is engaged on the front half of the small ring, but from there instead of going straight back to the rear derailleur, it's snagged on the middle ring bolts and pulled back up into the incoming part of the chain.

My bike has about 640 miles on it, but this has only started happening over the last 50 miles or so.

I clean the chain at least every other time I ride (every time when there's any mud) and I know I've ridden problem free in much nastier conditions ealier in the season.

Is this a form of chain suck or something else alltogether? This definition makes me believe it's that latter: http://www.***an.co.za/Bikes/Csuck/NOT-SUCK.htm

More importantly, does anybody know what I can do to fix it?

I have a FSA Afterburner MegaExo, 22/32/44.
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Old 09-18-08, 08:49 AM
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born2bahick
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I suspect a worn chain, and or chainrings over an adjustment issue. Pictures?
Also if the chain suck has happened a few times, check for bent, stiff or bad links in the chain.

Last edited by born2bahick; 09-18-08 at 08:54 AM.
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Old 09-18-08, 08:57 AM
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andymac
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That is an odd problem as the chainring bolts on most cranks are recessed enough that there would be very little chance of the chain managing to hang up on them.
Assuming that you do not have a problem where the chainring bolts are in backward or have backed off, I would suggest looking at where the low limit is set on your derailleur. You may want to adjust it so the derailleur can move in a little further so that it pulls the chain further away from the middle ring. This will only work if there is enough slack in the cable that it can move in. You would also need to make sure that the derailleur didn't move in too far, otherwise you will just end up dropping the chain off the small ring.
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Old 09-18-08, 09:58 AM
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I would replace those hex-headed Grade 5s with real chain ring bolts .
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Old 09-18-08, 11:55 PM
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If possible convert to single speed.

but if you want to keep the gears i would also guess a worn chain.
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Old 09-19-08, 12:25 AM
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And to add general advice. Try not to shift the front in an incline, where the shift would likely be under load because you need to maintain momentum. Instead, look ahead, and figure out what chainring you need to get up the climb, and shift there. It is far easier to shift the rear derailleur during the climb itself.
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Old 09-19-08, 09:08 AM
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miamijim
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when i had a similar issue it was due to 2 reasons....

1. too much crud on the chairings which in turn prevented the chain from properly relaesing off the chainring teeth
2. burrs on the chainring (from wear) which in turn prevented......

Thouroughly clean your chainrings and carefully inspect the teeth for burrs or wear ridges..
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Old 09-21-08, 12:31 PM
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Thanks for the pointers. I do have a few burs now on my chainring, so I'll start with those...
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