I bought a used gravel bike. A few days after I bought it, I took it apart to clean everything. That's when I noticed the damage here. I contacted the seller and he would take the bike back or reimburse me for the cost of a repair (if that is possible). How bad do you think the damage is? Can I continue to ride it? I had an Enduro frame with a small crack and I had no problems with it. A carbon specialist said at the time that carbon can withstand more than you think. But this is a road bike frame and not a thicker enduro frame.
According to the seller, the damage could have occurred when he was riding in ice and everything was full of ice. Because the chainring can't actually rub at that Point.
by xImDetox
18 Comments
Carbon is an awful material and you can’t really do a quick check with your eyes. This is only my opinion as someone who worked with a lot of carbon. It looks like the carbon got “rubbed” of, therefore the force was (hopefully) low and consistent and didn’t damage any other fibers in the area. The Carbon looks in good conditions, maybe get some filler and just cover it yourself. I would keep an eye on it (even tho it’s hard to tell) and keep riding.
I don’t have much advice, but that’s really interesting. First thing that comes to mind is the chainring contacting the chainstay but that would take ages like that.
It looks quite deep, keep in mind the frame is hollow and that is probably a significant portion of the wall thickness. If the seller is willing to take it back definitely do that. It seems like they know exactly how this happened. If you are stuck with it definitely get a pro opinion. What model is the frame?
OP that looks mostly fine. Depending on bike, you’re going to have 2-4mm of paint+clear coat which is what this looks like got rubbed off here.
For for carbon failing – you’ll either see cracks for delimitation or in the case of a cut, as is here, you’d see some of the fibers begin to protrude. This looks like it wore through the clear coat and the paint down to the raw carbon underneath. Whoever put your chainring on either put one on too big for the frame or didn’t know which spacers to use.
Folks downvoting me- I’ve dealt with carbon cracks, paint cracks and grooving like this before.
If he will take it back, bring it back.
I don’t know how thick the carbon fiber layup is in that location, but you can very clearly see several layers gone. For all we know, it could be worn almost all the way through, although more likely it’s like half-way through. In either case that chainstay is significantly weakened.
If it was my own bike, I’d probably ride it or maybe have it repaired because that location should be easy to do. But if you just bought it without knowing, and the seller is willing to take it back, then I would probably return it.
Opposite of good
Send it back
Real bad. Every chainstay-area tube I’ve seen from crashes, etc, has carbon thinner than that depth. That sure looks like an abrasion to me from an attempt to run a too-large chainring.
Send it back. It is repairable, but the repair is pretty involved, requires cutting through the stay, epoxying a carbon tube (or tubes) inside the stay, backfilling it with 2-part foam, then putting a (mostly cosmetic) carbon wrap around the cut and then repainting the repaired area if you care about cosmetics. A few hundred dollars, at least.
I wouldn’t ride it without repairing it.
Go ask your LBS about local carbon repair or look online. That should be a readily reparable area
If this was a private sale, you found an amazing seller to be willing to take it back. Most would consider finding visually apparent issues like this to be the due diligence of the buyer and the bike is sold as is.
if you can return it – you might as well. but – if you’re stuck with it – i honestly wouldn’t freak out that much. it looks very superficial.
get in there super close and look for signs the material is worn. experts on here will talk of paint as though it’s providing structural rigidity – that’s not what paint does. it provides oxidation protection. if it’s just paint it sucks, but it’s nothing .01oz of nail polish won’t fix. if you see it’s wearing into the carbon/aluminum/alloy/steel that’s different. your chainstays are hollow and they will fail suddenly/catastrophically.
if its just paint you’re fine, and to me it’s too close to call given the photos. if it’s into the material i’d take an expert opinion or in the absence of that not risk it.
Something ain’t right with that damage. I’ve worked as a professional mechanic for a decade now and here are my thoughts.
– That is a strange looking abrasion to me, idk how it could have gotten there. Every chainring biting into a frame I’ve seen is nowhere near as uniform as what is on your bike, and nowhere near as large of a damage area. In order for the chainring to cause that kind of damage in my opinion, would be from prolonged nearly constant grinding against the frame. And for that to happen you need to ask other questions about the bike, did the owner swap the bb, cranks, or chainring? Is the original spec that came on the bike what caused the damage, cause if so and you get it repaired it will just happen again.
– Is the bike a 1x or 2x set up? If you look closely at the second picture you can see smaller abrasions traveling up towards the large one. For those I could see a small chainring doing that damage, but if it’s a 1x system that is strange.
– Also if chainring rub is truly what caused this damage how could the rider have not felt the grinding of the chainring on their frame? There would be some serious drag from the constant grinding away of the chainring and frame. Do the chainring teeth look damaged, or dulled?
– This goes back to the original spec question, was the crankset tight and had no play? If the previous owner swapped cranks and bb or just cranks and didn’t check spindle length compatibility the crankset could have been sliding back and forth and then I would believe it was the chaining doing the damage. Still thought how does a rider not feel, hear, or notice the damage being caused?
– The excuse of it being really icy doesn’t make sense to me. And it could be that since I’ve lived in the south my whole life and have never seen what snow and ice can do to a bike, but where would the ice have been? On the chain, or the chainring itself? Do you live somewhere where it’s so cold that ice is so hard it acts as an abrasive and cleanly rubs down a carbon frame?
– That abrasion is so clean, I’m more and more skeptical about how it got there. Kinda looks like someone using an angle grinder went a little too far and hit the frame. Do you know the seller, how did they seem? What kind of deal did you get on the bike? It’s a little strange they offer to reimburse you for a repair if it’s stolen but who knows, they could just be pretending to cooperate and then ghost.
– I would try and figure out if it’s a stolen bike, if it isn’t and the bike is oem spec then bring it to a shop and figure out why the damage happening components wise and how much it would cost to change them to prevent this from happening again. Cause even if you repair it, if it truly is the chainring cause the damage it will just happen again and you need to address that.
– My shop has a borescope from Amazon we use to do various jobs with internal routing etc but carbon damage inspection is one of the things it’s been invaluable for. If you can find one (it was $50 for a good one on amazon) or a shop with one have them look inside the frame where that damage is. That will tell you how bad it is. It is common for frame manufacturers to reinforce that general area but since that damage is kinda far away from the BB it may not be reinforced dependent on what brand the bike is.
– Last thing, on the second picture it looks like there is a crack along the bb where it flares out to make room for bearings. Maybe it’s just an artifact from the picture or some piece of hair or whatever but I’d check that out.
Return it before he changes his mind and ghosts you. The thought of that thing will never leave your mind.
It only hurts if you let it
That is what my 1x drivetrain TCX would look like if I tried to put a 50+ tooth chainring on it and then ignored the grinding sounds while riding for many hours.
Unless it was an amazing deal and worth repairing I’d take it back