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How bad is this damage to the chainstay??

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How bad is this damage to the chainstay??

Old 11-12-21, 07:47 PM
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How bad is this damage to the chainstay??

Looks like maybe it's from the chain popping off and being ground a little between the frame and the chainring? It's the only blemish on an otherwise gorgeous bike.

I can't tell if the chainstay is actually dented or not either - or if it's just the cutaway to accommodate the inner chain ring? The gouges seem pretty gnarly - but I'm hoping it's mostly superficial enough that the frame is not compromised. Thoughts?





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Old 11-12-21, 08:12 PM
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Unlikely that will cause any issue possible except between our ears. It might start a crack that dooms the bike in 5-10 years from now but that breakage is unlikely to do more than be a ride ender. My Peugeot UO-8 broke there (after 19,000 miles and dozens of crashes from fatigue). Rode it home, no issues but I did ride gently.

I'd ride it, not think twice and try to remember to look at it every fifth blue moon or so.
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Old 11-12-21, 09:05 PM
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Looks more like a scrape than a gauge. If the frame is metal (aluminum/steel/CroMo), remove whatever paint flecks are there, sand smooth using maybe 600 grit wet/dry sandpaper, go get the closest match from the nail polish section at your local store and touch up as to protect the bare metal. Reassemble crankarm and chain, and adjust derailleur to prevent a 2nd. episode; now enjoy riding your bike with its first "battle scar".
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Old 11-13-21, 12:00 AM
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Yep... dropped chain got jammed between the crankarm and the chainstay.

Unless the frame is one of those stupid-light ~2 pound aluminum ones from the early 2000s, I'd sand out the cracked & flaked paint, touch it up with Testor's model paint or cheap nail polish, check it every so often, and ride it.

--Shannon
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Old 11-13-21, 01:22 AM
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Originally Posted by ShannonM View Post
Yep... dropped chain got jammed between the crankarm and the chainstay.

Unless the frame is one of those stupid-light ~2 pound aluminum ones from the early 2000s, I'd sand out the cracked & flaked paint, touch it up with Testor's model paint or cheap nail polish, check it every so often, and ride it.

--Shannon
it IS a 2001 Cannondale R1000. So, yeah it’s one of those I think…
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Old 11-13-21, 07:51 AM
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Clean the site and if it is only a small gouge and you do not see a stress riser (a crack) you should be fine. Being aluminum just keep an eye on it and enjoy.
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Old 11-13-21, 10:38 AM
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Originally Posted by the sci guy View Post
Looks like maybe it's from the chain popping off and being ground a little between the frame and the chainring? It's the only blemish on an otherwise gorgeous bike.

I can't tell if the chainstay is actually dented or not either - or if it's just the cutaway to accommodate the inner chain ring? The gouges seem pretty gnarly - but I'm hoping it's mostly superficial enough that the frame is not compromised. Thoughts?




I’ve seen much worse on aluminum frames. The “dent” is OEM. The gouges aren’t.

The gouges look like classic “chain suck”, which indicates there is likely a burr on the chainring that is catching the chain. The chain releases late (or not at all) and gets trapped between the frame and ring. Sometimes the chain is stuck in there pretty firmly and has to be pulled out by hand. Often it will just pull out on its own. It’s hard to say which happened in this case but you can see the paint is pulled “up” by the chain and the metal is pulled down by whatever method was used to get the chain free.

Overall, it’s not a problem for the frame but I’d check the teeth on the inner ring for burrs. Sometimes you can actually see the burr but often you have to use your fingernail and see if you can find a tooth that catches your nail. If you find one use a fine file to remove the burr.

I wouldn’t try to “fix” the gouges or the paint. It’s just part of the patina of riding. Trying to sand or smooth or remove the gouges is just going to remove metal. Aluminum will corrode if exposed to salt and water but it’s a pretty slow process. I wouldn’t even be concerned if I were to use this as a winter bike, however. In normal riding, he aluminum has already formed an oxidized layer just through air exposure so it isn’t going to corrode it any further.
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Old 11-13-21, 04:46 PM
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Originally Posted by cyccommute View Post
I’ve seen much worse on aluminum frames. The “dent” is OEM. The gouges aren’t.

The gouges look like classic “chain suck”, which indicates there is likely a burr on the chainring that is catching the chain. The chain releases late (or not at all) and gets trapped between the frame and ring. Sometimes the chain is stuck in there pretty firmly and has to be pulled out by hand. Often it will just pull out on its own. It’s hard to say which happened in this case but you can see the paint is pulled “up” by the chain and the metal is pulled down by whatever method was used to get the chain free.

Overall, it’s not a problem for the frame but I’d check the teeth on the inner ring for burrs. Sometimes you can actually see the burr but often you have to use your fingernail and see if you can find a tooth that catches your nail. If you find one use a fine file to remove the burr.

I wouldn’t try to “fix” the gouges or the paint. It’s just part of the patina of riding. Trying to sand or smooth or remove the gouges is just going to remove metal. Aluminum will corrode if exposed to salt and water but it’s a pretty slow process. I wouldn’t even be concerned if I were to use this as a winter bike, however. In normal riding, he aluminum has already formed an oxidized layer just through air exposure so it isn’t going to corrode it any further.
great info, thanks.
ill check the chainring but I’m not super concerned at the moment because I’m swapping everything out for modern 105.
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Old 11-13-21, 10:03 PM
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Originally Posted by the sci guy View Post
it IS a 2001 Cannondale R1000. So, yeah it’s one of those I think…
A lot of the internet talk of CAAD durability was for later model CAADs, beginning with the CAAD7. Most of the concern were about the thinnest of the top & downtube.

Regardless, the stays are not as thin and 'minor' damage is not a concern. Try tapping on the tubes and you'll hear the difference in thickness compared to the downtube.
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Old 11-13-21, 10:07 PM
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Being highly engineered aluminium, it's going to be prone to fatigue. If it was me, I'd try to remove the stress risers if they're not too deep, at least smooth it out a bit.
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Old 11-15-21, 10:19 AM
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For what it's worth, just about every bike I work on at the Bike Exchange has the paint worn off in that location and often there is some gouging. These are 30 - 40 yr old steel frames bikes and the damage has been there for years. I will sand or file down the rough area and spot prime / paint it. For and aluminum frame , inspect and file down rough areas, then prime/ paint. As mentioned previously watch for stress cracking.
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Old 11-15-21, 10:25 AM
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Originally Posted by Kimmo View Post
Being highly engineered aluminium, it's going to be prone to fatigue. If it was me, I'd try to remove the stress risers if they're not too deep, at least smooth it out a bit.
The concern that I have is that removing the stress risers will probably introduce other stress risers. The stress risers from the gouges are rather randomly oriented. A file introduces oriented stress risers. To my way of thinking, random is better than oriented.
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Old 11-15-21, 12:34 PM
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My Litespeed frame has some slight scuffs similar in the chainstay area from likely chain suck. About 2 minutes with a red scitchbrite smoothed it out. May be better than sandpaper for your application.
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Old 11-15-21, 05:37 PM
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Originally Posted by cyccommute View Post
The concern that I have is that removing the stress risers will probably introduce other stress risers. The stress risers from the gouges are rather randomly oriented. A file introduces oriented stress risers. To my way of thinking, random is better than oriented.
I'd use a knife to trim off the burrs and tickle it with an orbital sander.
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