Dale-Murray

I have a 2007 Lemond CF bike.

Unfortunately when my bars (end of the drop bars) swing hard left or hard right - like when carrying upstairs - swings into the top tube. I have dinged away some of the finish. Tonight, while carrying upstairs, AGAIN, they swung and hit, this time I can see a speck of the CF under the paint. The speck is about .3mm in diameter - so it appears no major damage.

(two flights of curving stairs, btw)

Questions:
- How concerned should I be at this time?
- Should I do anything to seal the carbon (though, I doubt I have broken through the outer coating) - clear nail polish?

For the time being I have taken a piece of high density foam and taped it to the top tube for protection until I come up with a more elegant solution.

cuevélo

1. Probably nothing, but if you are worried, take a nickle and tap the tube far from the nick. Work your way all the way to it. If the sound changes dramatically then it is delaminated.
2. If the solvent in the nail polish is acetone, you shouldn't use it. It can be bad for the resin. I wouldn't do anything for fear of melting the plastic.

Maybe you could put a few wraps of foam bar tape around the TT so it doesn't happen again.

BCRider

A wipe of acetone won't affect the epoxy resins used to form the carbon. Soaking long term may do some bad stuff but a few seconds to a minute or so won't do diddly on it other than softening the outer clear coat perhaps. Not even much certainty that it will even strip off the clear coat if it's a two party polyurethane. I'd want to talk to a good autobody paint guy before deciding to add anything to the clear coat.

If that last ding looks to be at all dull looking at the bottom of the ding then I' suggest some good quality laminating resin and mix up a small 1/2 oz batch and then use a whole single drop to seal the divot you created.

And I'll also second the use of a couple of wraps of bar tape sealed with some electrical tape that runs slightly onto the top tube so it's sealed from the usual rain to avoid a second ding of that nature. One ding that reaches the carbon with such a small size is very likely not an issue. But if you allow this to continue and enlarge or open other dings then it could soon develop into something to worry about.

tommy gayle

I have a question about the new carbon fiber bikes
can you use the fiberglass resin on the bikes surface much like you can on a boat
and if you can then can you repair the cracked frames with the fiber mat the same way that you repair a boat nick or scrape??
thanks for your answers

dabac

Well, sort of. FG is usually used together with polyester resin, which is a slightly different animal than the epoxy resin used together with CF. Poly is weaker, more brittle among other things.
It probably won't bond quite as well to an epoxy laminate as an epoxy repair would.
Using epoxy to fix a poly structure OTOH is no problem.
Otherwise the CF fiber mat behaves pretty much like the FG mat.
The biggest issue is the different strengths in CF laminate and FG laminate.
For a FG laminate it's enough to scarf a joint 10x the thickness of the laminate to create a joint that's virtually indistinguishable from the base material in strength and material properties. For a CF laminate you need a 40x the thickness to get a (strength-wise) smooth transition between patch and base material.

Wanderer

Here's what I do to keep the front wheel from swinging.

Take one of those very small bungee cords, the little bitty ones, and pass it thru the spokes. Then pull it thru the downtube and fasten it to itself, with it's own little hook.

NO more bar swing. I use this when hanging bikes on my stand. Works all the time. Sure should work well for carrying.

waterrockets 

Good tips above on dealing with the carbon.

To carry your bike up stairs, grab the seat tube pretty low with your near hand (straight arm), and hold the bars up with your far hand. This will get the bike at a good angle to go up the stairs without being too high, and will prevent the swinging.

If you must shoulder the bike for some reason, consider doing so backwards so the front wheel hangs and won't turn the bars into the frame.

Yeah, but then you can't roll the bike without removing the bungee.

tommy gayle

thanks on the info on the resin that help me on the thought of getting a resin bike over a metal bike I was not sure as I am heavy and did not know about repairs if I broke it

Dale-Murray

I have never had an issue like this before - for whatever reason I just keep doing it; it is like I keep biting the inside of my mouth. Part of the problem is I have to negotiate four turns on the stairs then rotate the bike 180 degrees to hang it on my rack in the hallway.

I am going to cut a couple squares of high density rubber and rubber/contact cement them to either side of the top tube. That will take care of the bar end cutting into the TT.

I hope to replace the bars with something I like better next year and hopefully that will alter where they hit, too.