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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 07-02-11, 09:39 AM   #1
and1homer
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Hey BF, is my chainring FUBAR?

I had my LBS put a new chain on a month or so ago, and ever since have had problems - chain jumping, skipping, dropping etc.

I took a close look today and it looks like a couple of rivets may have have sheared or bent and the chain is definitely sitting on top of the chainring at one specific spot.

Check these pics:









Once every rotation the chain sits up on top of the chainring teeth rather than in them, causing a skip every rotation ... in this vid it happens when the chain meets the crank arm on the opposite side of the bike from the camera.


So BF, please help me - is this a tuning issue, a chain issue, or a chainring issue? Is my chainring FUBAR? Please help! Thanks
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Old 07-02-11, 09:56 AM   #2
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i would look for a bent tooth right where that shift gate is and where the chain starts to ride up. bend it back and file off any burs.
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Old 07-02-11, 11:49 AM   #3
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+1, A bent tooth, or possibly the first tooth after the gate having a square or split top catching and lifting the chain rather than letting it slip down and engage smoothly. Straighten if needed and file the sides at an angle to form a point.
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Old 07-02-11, 11:56 AM   #4
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also my favorite chainring persuaders are the rubber mallet and pin punch

Last edited by reptilezs; 07-02-11 at 01:01 PM.
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Old 07-02-11, 12:39 PM   #5
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Very useful, thanks. I will check for a bent tooth, see what I can do with it.
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Old 07-05-11, 09:49 PM   #6
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Well, I tried it myself but didn't really have the right tools. Took it to LBS and they confirmed the bent tooth, and fixed it on the spot. Thanks BF, you all rock!
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