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What happened to my big chainring? Easy fix?

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What happened to my big chainring? Easy fix?

Old 04-23-08, 11:01 AM
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D.J.M.
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What happened to my big chainring? Easy fix?

On the couple of last rides I noticed that the chain was scraping somewhat along the front derailleur.

I didn't give it much thought except I tightened up the wire to the rear derailleur and moved the chain a bit out and away from the front derailleur, thusly bringing an end to the scraping.

However yesterday I was even more troubled. The scraping was still there and the chain jumped off on a couple of occasions.

Inspecting the bike today I noticed that the large chainring was noticably bent sideways in one location. The smaller inner ring is not bent.
I haven't had any falls or bumped into anything before this happened.. so how did torque bend my chainring?

I'm 200 pounds and climb a lot.. Presumably the bike should handle that well, at least the chainring.


Anyway -- is the large chainring on a 50/34 compact an LBS staple, and does changing it require much labor?
It sits on an FSA Gossamer crank, seemingly attached with five bolts.

I will of course consult my LBS tomorrow... but I thought you could perhaps bring peace to my mind :-)

Thanks in advance!

Last edited by D.J.M.; 04-23-08 at 11:21 AM.
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Old 04-23-08, 11:17 AM
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If its the chainring thats bent its an eazy fix, like you said undo the 5 chainring bolts and the chainring will slide off over hte crankarm then either try straigthening it or replace it with a new one. (hopefully its just the chainring)

BTW mine is bent also but not enough that it effects its function adversly
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Old 04-23-08, 11:18 AM
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Its cheap to replace a chainring, assuming that is the only problem.

Congrats on having the watts to bust your chainring.
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Old 04-23-08, 12:20 PM
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I'd be worried that the bottom-bracket axle is getting bent, or the crank-arms themselves are loose -- i.e., something that puts some sideways torque into the chainring.

Replacement chainrings are widely available, and it's an easy fix. Whether or not they have a 50-tooth ring in stock is another question. I'd have them check the torque on the bottom bracket and crankset assembly though while they're at it.
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Old 04-23-08, 12:24 PM
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Originally Posted by D.J.M. View Post
I'm 200 pounds and climb a lot.. Presumably the bike should handle that well, at least the chainring.
Thanks in advance!
Impressive, keep hammering
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Old 04-24-08, 03:06 AM
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D.J.M.
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Thanks for the help guys!

I just spoke with the LBS and they said that, while mounted, they would hammer the chainring straight using a rubber hammer... is that safe on a carbon frame..??
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Old 04-24-08, 06:08 AM
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Originally Posted by D.J.M. View Post
Thanks for the help guys!

I just spoke with the LBS and they said that, while mounted, they would hammer the chainring straight using a rubber hammer... is that safe on a carbon frame..??
I imagine they're going to take the chainring off first... It would be pretty hard to get any type of leverage if it's still on the bike.
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Old 04-24-08, 06:53 AM
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D.J.M.
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Hehe... That's what I said to them.. though I didn't talk directly to a mechanic, only a seller out in the store.

I'll find out in a couple of hours..

BTW - What kind of lead times do you experience on service at the LBS?

For something like this simple fix they scheduled me to pick it up at 1700 tomorrow, having delivered it 1000 today. Though, I was told to drop by or call them by the end of today. It's their busy season, but I guess I may be spoilt by my old repair shop which would sort out things like this in a matter of minutes. Sadly they closed.
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