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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!!

Here are some pics:

  • I can't tell exactly what part of the chainstay this is from these pictures. Does the wheel sit in that gap? It looks like the tire has been rubbing there. – Unknown Zombie Jun 18 '15 at 14:28
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    Yep, the wheel sits in that gap. Tire rubbing is the first thing that came to mind to me as well. Would it be safe to continue riding still? – user20041 Jun 18 '15 at 14:30
  • Most likely your tire was rubbing the chainstay and it deposited rubber where it rubbed. Align and/or true the wheel and there should be nothing to worry about. – Carey Gregory Jun 18 '15 at 15:30
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    Bikes are made to handle a lot of stress so you're probably good, but it looks like the rubbing is not superficial and part of the inside carbon was removed. Why don't you ask Cannondale? Send them an email. Also, I would think about changing bike shop: if you went there when a problem was visible, they told you it was good, and it eventually became like this then they made a bad assessment of what was going on. If the wheel is rubbing the frame there has to be an issue somewhere. They should have at the very least trued the wheel. I personally would go there and show them. – super Jun 18 '15 at 22:22
  • Thanks everyone for the replies. I've rechecked everything, reseated it and tightened the skewer to make sure everything is in the right spot. Going to add tape over the spot and monitor it to see if the problem still persists. – user20041 Jun 19 '15 at 2:49
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I have a Cannondale Supersix Evo and I've had issues with tires rubbing in that exact spot. The frame will accommodate a 25mm tire, but the clearance is very tight, so you really have to pay attention to keeping the wheel trued up. I've also found that the stock wheelset (Mavix Aksiums) flexed enough when I'm cornering hard to cause a little rubbing even when the wheel is near-perfectly true. For a little while, I put some protective tape on the chainstays (I used ISC Racers Tape), but I eventually just switched back to 23mm tires. I like the ride quality of the wider tires, but replacing the protective tape periodically got to be a bit of a hassle.

To answer whether or not it's safe to ride, it LOOKS like it's just through the paint. If that's the case, cover it with some protective tape to prevent it from rubbing into the carbon, and you should be good to go.

  • Tape's a bit of a bandaid fix. The smaller tyre would be the right answer, but if that's not acceptable perhaps gently clamping a jubilee clip around the chainstay would help. That way the rub would be onto steel not on thin tape. Of course this would decrease the space even more. There are adhesive metal tapes that exist which may be a good halfway point. – Criggie Nov 5 '15 at 20:33
  • @Criggie what's a jubilee clip? – dlu Nov 6 '15 at 11:52
  • Jubilee clip = hose clamp. The problem with that is that they're very abrasive, so if the tyre rubs on the clamp it will get ground down very quickly. Could go through a lot of tyres. – Móż Nov 6 '15 at 21:07
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It's identical to what I have on my cyclocross bike from running too wide tires, except my rub damage is to aluminum. Since you already checked the skewers, check the dish of the wheel to see how close its coming to the chainstay, also check if there is play in the axle/hub, that may cause extra flex. A lot of power can cause frame flex and tire contact. Those tubes down there are pretty beefy, but a lot of rub will grind right through. I'd say its safe, for now, but keep an eye on it.

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Short answer: Yes it is safe to ride on it for another thousands of miles.

That is the tyre rubbing mark. This happens when the clearance is too little to allow any error in assembling the rear wheel.

I have repaired a few carbon frame and happy to tell you that it is very likely that the damage is superficial. It appears to be a smooth surface, which means the worn out part is still at the epoxy/laminating epoxy resin.

Just make sure that the wheel is true, and assembled correctly to prevent further damage.

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If you look closely (especially at the last pic), you can see that the tire has rubbed into the fourth layer of material. Black, white, black, gray.

It's clearly gone into the carbon.

I would take it over some harsh bumps, to stress the frame beyond anything it would experience normally. If that works out okay, put some tape over the spot and don't worry about it.

(And, of course, true your wheel.)

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Check the axle has not drifted over. You need some cone spanners and you can check. There should be the same amount on both sides where the axel fits into the dropout.

Another point is the dishing of the wheel. Rear wheels are usually dished slightly over . If you have done some wheel truing lately or someone else has, make sure its not dished too far over.

Check there isn't a small buckle in the wheel hitting at that point only.

Another idea is to change down the size of your tyres as previously mentioned, or go for a slicker tyre.

Short term solution to protect the frame is put some gaffer on it but to be honest your tyre shouldn't be rubbing, especially not on carbon.

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Looks like the finish is rubbed off. You should seal the carbon fiber to protect it from water. Water will cause the carbon fiber to swell. You can seal with nail polish or a lacquer. This is a video on repair.

I think tape (alone) is a bad idea as it will hold moisture. I think a jubilee clip is a bad idea as it will tend to crack the finish.

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It looks like the tyre has rubbed due to the wheel being pulled over,this is caused if the skewers were not tight enough.recentre the wheel and re tighten the quick release skewers

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