Hey All. So my chain dropped inside toward the bottom bracket, and tore up my chainstay some. Photos attached. It’s not soft at the spot but it is pretty roughed up. Do you all think it’s ok to ride? If not is Home repair an option?

If it was My bike I’d curse a little, then keep riding.
A failure there - unlikely as is seems Judging by the pic - is rarely instantly catastrophic.

Ugh. bye bye. Hope it doesn't happen to me. Maybe a chain catcher is a good idea.

I would not ride it.

In that spot, a home repair would be difficult. Too much material and you'll run into the chainring.

Ruckus Composites does carbon frame repair: Carbon Fiber Bike Repair | Ruckus Composites

Not a good thing.

You might have it patched by someone who knows what he's doing. Odds are it can be restored to good as new condition.

Or you can do a DIY repair or ride it as is, knowing it may be compromised in a way that will lead to failure eventually. Eventually can be a long time out, and the nice thing about chainstay failures is that they don't tend to have consequences other than having to walk home.

If it were mine, I'd probably do some kind of DIY patch, maybe using something like muffler tape.

FWIW - your issue illustrates one of my pet rants against CF frames. There's nothing wrong with CF per se, but makers haven't given enough though to real world hazards. We all know than chains fall of, or there's something called "chain suck" and whatever. So, knowing there's a reasonable risk of the chain "attacking th chain stay in that area, I'd expect (demand) some kind of ballistic layer to prevent damage. The added weight and cost would be negligible, but makers don't seem to care for their customers that much.

they usually have a metal plate stuck in that area mine got chomped up a couple of times before i removed it and put on a chain catcher, if it was my bike I would keep riding it and maybe wrap it in black duct tape for aesthetic purposes and to minimise any more damage if it drops again before you install a chain catcher.

That looks like it went through quite a few layers. I would not ride that.

It may be possible to do a home repair if you have some experience with carbon composite materials. Otherwise I'd find a pro.

Given its behind your crankset, it does not even have to be that pretty a patch,

but given the BB-Chainstay is where the force is applied, it better be a quality job, structurally ..



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Or even fiberglass composites.. .. ? any experience in working with patching up Boats?

I'm a retired yacht builder with lots of experience with boats. I also worked at a composite shop doing work for the Navy, Boeing, McDonald Douglas and NASA. FRP composites and carbon composites are similar. If you can do the one, you can do the other.

Fiberglass can act as a safety net if it cracks, but won't provide structure because of the difference in flex properties. The stiffer CF takes most of the load on it's own before the fiberglass begins to take up any. So rather than working together they break in sequence.

But Berner is right, the process is similar, and if one has some hand skill and sources CF patch sheets and resin, it's not really a difficult DIY repair.

Yea , wet laminating skills, if any, would be useful ,, FWIW, one of my friends did a rudder repair on his Sail Boat ..

Wrapped it with fiberglass and used Epoxy , mostly because, even working outside, the polyester resin is much more odorous..





using Fiberglass is also used as insulation between 7000 series, Zn containing Aluminum alloys and Carbon cloth..

because a C & Zn combination is a battery when stacked up with enough alternating layers...

youngsters may not remember old flashlight batteries were made of those 2 elements..











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Yeah, dropped chains aren't built into the frame design.

My LBS added a chain catcher to my new bike without asking me first, so they probably do this to all their new carbon bikes. The carbon frame is very wide down by the bottom bracket, and the gap between frame and crank tapers down to a slot narrower than a chain. So any dropped chain is going to jam in there and do some damage.

These catchers wouldn't prevent "chain suck", though.

Chain suck
The OP's damage does look like chain suck, since it's at the chain stay, not in front of the bottom bracket. This chain suck article lists the causes:
Front shifting under heavy pedal load.
Worn chainring.
Chain maintenance.

Dropped chains are preventable, as is chain suck. But they happen. Likewise, preventing damage from either is easy, so IMO there's no reason to go offer a greater level of protection.

It's sort of like RD hangers. BITD steel frames had integrated hangers. Sometimes the RD would get caught and bend or break the hanger, the latter being an expensive repair. n So, we now almost universally use breakaway, replaceable hangers. However, nobody yet seems to care that much about easily preventable chainstay damage.

My CF bike damaged twice. Once when carrier clamp can loose on 1,000 mile trip and wore thru top layer. Next bike carrier latch failed and lost bike at 40 MPH. Both damaged area looked BAD. I finally stopped crying and patched both damaged areas with nail polish. Couple thousand miles later and nail polish still looks good and frame is still solid and rideable. Note both bike carrier failures were operator error that will NOT happen again.

Uh-huh. Nail polish will "fix" a scratch, but what the OP's picture showed is structural damage in a pretty highly-stressed area. IMO, it requires evaluation and repair by someone who knows composites.

FWIW: the carbon-fiber frames I'm familiar with typically have an outer layer that is decorative and/or protective. This can be either a light "veil" cloth or just epoxy. Wearing through or damaging this usually won't compromise the frame.

Think about this, how thick is the carbon in that chainstay? How much has already been removed by the damage? I would guess that there is no more than 5mm of carbon left in that chainstay.

Thanks everyone! I decided to take it to a local carbon repair shop that has lots of good reviews from cyclists. While I think I could likely do the repair myself, I’m going with the piece of mind of a pro job. I love my bike, and want it to last, so I think this is the best option.

ummm... did you mean POINT 5mm? as in a half millimeter?

because 5mm of carbon fiber composite REMAINING is a damn thick chain stay wall....

If it was just the first layer or two is cosmetic and I'd say you'd be OK. I have a Tarmac that's through the cosmetic layers and I can see the structural layers, but there is no damage.

That being said, what you posted in the pictures looks like structural damage. I wouldn't ride it. There are several frame repair shops around the country that should be able to fix it for probably a few hundred dollars. I'd do a google search and send pictures/quote requests to 4 or 5 of them and see what you get back.