Bicycle Mechanics - Groove in Carbon

When my carbon bike was put together last spring they routed the front derailer cable wrong. Under the bottom bracket is a hole that the cable is supposed to run through. They didn't run it through that hole, and as a result there is a slight (very slight, but visible because of the colour and your nail catches it) groove in the carbon.

I've talked to the bike shop who takes full responsibility for it, and the manufacturer is now involved. I emailed them pictures yesterday and I'm concerned they will say that it's a minor groove and not structurally an issue. I hope they won't, but you never know.

I've attached a picture of the bottom of my bike, and I drew a very professional arrow to the groove.

I've read that carbon is super weakened by any breach in the body. I don't want to get into a carbon sucks thread, but I'm curious about a) whether this is a serious issue and b) because of where it is, if they don't honour a warranty claim and I don't feel like going to small claims court, then is this still safe to ride?

Thanks!

Looks like a non issue to me.

yea, I wouldn't sweat it.
Hit the macro setting on your digital camear (flower pot symbol) and take an extreme closeup.

While the groove is less than ideal, it's not in a highly stressed region.

Thanks for the input, I'll try that camera setting to get a better shot.

Should I put something like clear nail polish over the groove? My thought being it would fill it up as well as add some strength (maybe?!)

Should I put something like clear nail polish over the groove? My thought being it would fill it up as well as add some strength (maybe?!)

Nail polish will not add strength. It would fill the groove and keep crud out though which couldn't hurt. If you are that worried I recommend you dab a little clear epoxy in the groove - clean with alcohol first. It will hold up better than finger nail polish and won't be affected by solvents/oils that may hit the frame in that area.

Nail polish will not add strength. It would fill the groove and keep crud out though which couldn't hurt. If you are that worried I recommend you dab a little clear epoxy in the groove - clean with alcohol first. It will hold up better than finger nail polish and won't be affected by solvents/oils that may hit the frame in that area.

Would you recommend the epoxy, or just not bother with it and keep everything clean as I'm supposed too?

While the groove is less than ideal, it's not in a highly stressed region.

That's my take also. Cover the groove with clear nail polish as you said. If the manufacturer is willing to make an adjustment, fine, but otherwise don't worry.

I would not use nail polish. It is primarily Acetone which is a solvent for the epoxy resins in the carbon frame. I would smoothly cover the groove with more epoxy, not with its solvent

I would not use nail polish. It is primarily Acetone which is a solvent for the epoxy resins in the carbon frame. I would smoothly cover the groove with more epoxy, not with its solvent

Well that's very good information to know!! Going to the hardware store, is there a specific type of epoxy I ask for?

The stronger/harder ones are also the longer setting ones. If you're not in a hurry I'd use the strongest one available in a convenient small container. (I like those double-plunger dispensers. I keep those around for general purpose repairs. I also have stronger stuff I used to use for golf club assembly)

The stronger/harder ones are also the longer setting ones. If you're not in a hurry I'd use the strongest one available in a convenient small container. (I like those double-plunger dispensers. I keep those around for general purpose repairs. I also have stronger stuff I used to use for golf club assembly)

So, go to the local hardware store, ask for clear drying epoxy that is in a small container and the strongest possible? Is there a brand that you use?

Can I use this stuff on an Aluminum bike too? I saw a hairline crack starting at around the seat post that I'd like to just firm up.

Can I use this stuff on an Aluminum bike too? I saw a hairline crack starting at around the seat post that I'd like to just firm up.

:eek: Whoa there. It is not a cure-all. If you have a crack in the seat stay area of an Alu frame, which is a highly stressed area, the frame is toast & no amount of epoxy will "fix" it.

:eek: Whoa there. It is not a cure-all. If you have a crack in the seat stay area of an Alu frame, which is a highly stressed area, the frame is toast & no amount of epoxy will "fix" it.

Oh well, can't hurt asking! :)

I would not use nail polish. It is primarily Acetone which is a solvent for the epoxy resins in the carbon frame.


No, it's not . Nail polish will be fine an is, in fact, a suggested touch up for many a carbon mfg.
Really, it's the equivalent of a paint chip. I've seen frames with busted tubes that had carbon fragments threading out of the crack and people still rode them home.
Just dab that thing with nail polish and stop worrying.

No, it's not . Nail polish will be fine an is, in fact, a suggested touch up for many a carbon mfg.
Really, it's the equivalent of a paint chip. I've seen frames with busted tubes that had carbon fragments threading out of the crack and people still rode them home.
Just dab that thing with nail polish and stop worrying.


My bad. I misspoke. Nail Polish REMOVER is primarily acetone. Nail polish is more like a varnish and would probably be just fine. But I would still lean toward a long setting epoxy

I would go to a boat store and buy a 2 part epoxy. I think it's called called System 3. It's clear and they sell it in small packets. It use to be $10.

My bad. I misspoke. Nail Polish REMOVER is primarily acetone. Nail polish is more like a varnish and would probably be just fine. But I would still lean toward a long setting epoxy

Acetone only dissolves epoxy before it is cured. After it's cured there is no prob using acetone to clean it

I would not put anything on a new carbon bike until I asked the factory rep. Having done that, if he has no objection I would use a good name brand epoxy. Devcon makes industrial strength 2 part epoxies that are made for specific materials. Another good one that has been around a long time and I have used on various material (but not a carbon frame) is J&B weld. You can get it at the local auto parts store.

I've actully used nail polish to keep a carbon seat post from sliding down in the carbon seat tube. No problem with it and it works well. In terms of epoxy on the groove, it will fill and perhaps cover better than nail polish, but provide no real strength. The strength in carbon fiber is not from the epoxy in the matrix; it's from the carbon fibers. I suspect the others are correct in the assessment that this is not a high stress area. If it were mine, however, I'd push for an extended frame replacement warranty as a bottom line, and hope for a frame replacement.

I think you would be better off doing nothing to the groove until you get an answer from the FACTORY---messing around with stuff like that just may be a cause for them to void the warranty.

Especially if the bike shop accepted the responsibility for the mistake---I personaly think you are due a new frame--just think how deep the groove might have gotten if you haven't found it. The bike shop should honor the replacement.

In terms of epoxy on the groove, it will fill and perhaps cover better than nail polish, but provide no real strength. The strength in carbon fiber is not from the epoxy in the matrix; it's from the carbon fibers.

For the record, carbon fibers alone have great tearing strength but no rigidity. It's basically just fabric. Rigidity comes from the hardening agent.

In the OP's situation, though, the nail polish or epoxy would perform the function of a clearcoat, which is protective and cosmetic, but not structural.

Bob