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Re-Aligning a Wobbly Chainring

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Re-Aligning a Wobbly Chainring

Old 06-28-06, 11:05 AM
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Re-Aligning a Wobbly Chainring

When building my latest bike, I noticed a slight side to side wobble in the large chainring - maybe 1-2 mm. I was able to adjust the drivetrain around it and proceeded to ride. Today, a week later, the chattering in the front der could not be trimmed out because the wobble is now about a good 4 mm. Not sure how it increased as I certainly don't have that kind of power.

What's the best way to bend this sucker back into alignment so that it will stay? Is this even possible for a DIYer? How about the LBS - would they have a tool or a technique that would ensure proper alignment as opposed to just "eyeballing" it?

Thanks!

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Old 06-28-06, 11:22 AM
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Rad - I posted some hopefully helpful info over in your thread on the Road forum. In short - search Sheldon Brown's website for very useful info on how to fix the crank up good as new.
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Old 06-28-06, 11:33 AM
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Before you bend the ring make sure that the crank is installed square on. To test, mark the outy bit of your ring. Remove and rotate it 2 bolt holes around. Does the outy part stay with the crank or move with the ring?
If the ring is the culprit, test for flatness on a glass surface.
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Old 06-28-06, 12:27 PM
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Originally Posted by MichaelW
Before you bend the ring make sure that the crank is installed square on. To test, mark the outy bit of your ring. Remove and rotate it 2 bolt holes around. Does the outy part stay with the crank or move with the ring?
If the ring is the culprit, test for flatness on a glass surface.
+1
It seems unlikely that a ring would bend from 2 mm to 4 mm just because you rode the bike. That sounds more like something is coming loose. Bottom bracket?

Al
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Old 06-28-06, 04:44 PM
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Originally Posted by Al1943
+1
It seems unlikely that a ring would bend from 2 mm to 4 mm just because you rode the bike. That sounds more like something is coming loose. Bottom bracket?
That's what I think too. The first thing that I'd do would be to check all of the chainring bolts and the crank bolt.
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Old 06-29-06, 10:15 PM
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Followup - it turned out the bottom bracket - Italian thread - had pedaled itself loose. After a re-install - this time with threadlock tape - I'm back to just the tiny wobble i started with. And since I can adjust it to work without any rub, I'll leave it for now.

Thanks all for your help.

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