adrw.hong

I was cleaning my road bike (cannondale supersix evo) and noticed a marking on my chainstay and I'm not sure what it is. Scratching it is a little rough compared to the carbon around it. This was not there before

I did take my bike into the shop a few months ago, since the wheel was sitting really close to the non-drive side chainstay, and they said it was a non issue. This was when it only had a small scratch. Now it's turned into something like this.

Should I be concerned? I have a big ride coming up and don't wanna miss it!

bt

tire rub

Smokehouse

Yeah...that's what it looks like to me too...what size tire are you running?

big chainring 

It's the beginning of the end.

adrw.hong

I'm running 700x23s.. is it still safe to ride?

Smokehouse

A 23 huh? Hmm...that shouldn't be rubbing at all. Even if you were a seriously heavy rider and running the tire at low pressure, it would bulge on contact, not at the chainstay.

I'd check wheel alignment, wheel true, etc. Something is causing it to rub.

As for riding? As-is I feel it is perfectly safe to ride...but that's just my personal opinion so take it for what it's worth. If you can solve the problem, I'd just keep an eye on it from time to time.

If it continues to chew away at it? No...it will eventually ruin the frame...

bobones

It's pretty severe tyre rub. Did you taco a wheel and ride it for a number of miles? I would definitely have no worries about riding with this however.

adrw.hong

I'm going to stick a little gaffer's tape in that spot and continue riding then.. I usually pump them up to 110PSI but I'll drop it down a bit to see how that goes. Wheel is true, aligned, all seems well from what I can tell.

Not that I can recall

Smokehouse

Try putting something sticky/greasy/whatever on that spot and go for a short ride. Ride as you normally would and then have a look. See if it rubs off on the wheel somewhere. (obviously clean it off when done...but I'd want to know where the components are hitting each other.



One last thing...you don't, by chance, have a spoke magnet sticking out...do you? The gap on my wheel/chainstay is so tight on my Tarmac that if I don't rotate the speed sensor magnet in a bit, it will definitely hit the chainstay...on the crank side.

cale

It's nothing to worry about and it usually happens because the rear wheel skewer isn't tight enough. If you transport the bike, remove the wheel for whatever reason, the amount of pressure put on the wheel will vary a bit. Too light and the wheel will get "dragged" over to the left inner side (viewed from behind) when you're jamming up a hill or sprinting.

Edited to add... I've been thinking. The vertical rear dropouts aren't like the horizontal dropout I might have been thinking of so is it possible that the wheel itself gets pulled over? Depends on strength of wheel vs strength of rider, haha.

adrw.hong

Hmm.. I do have a spoke magnet but its not sitting too close to the rim. I'll double check that though.

Thanks for everyone's suggestions! I'll try a few things and report back.

banerjek

Looks like tire rub -- probably the bike was ridden for a little while with the wheel not installed properly. Once this was corrected, the problem no longer existed which is why you're not seeing the cause. I don't like the magnet idea nor do I think it's anything like the back of a brake pad hitting because the spot is smooth -- these other causes would have led to chipping. I wouldn't worry about it at all.

Smokehouse

Yeah...a magnet would not only make a distinct "click-click-click-click" sound while riding...it wouldn't make a smooth grind either.

Jiggle

Can be a result of the drive side spokes losing tension.