Is it normal for carbon fiber wheels to absorb water? I took my (brand new) carbon wheels on a century ride this weekend and it rained the whole time. Upon returning home, I noticed that the wheels appear to have a bit of a rime line on them(you know, that irregular white salt line) and were darker in some places along the seam than others. While cleaning the bike, I noticed that the seam appeared to get dark, as if it was absorbing water, when I wiped it with a damp sponge. They do not appear to be swelling or warping or anything like that, nor do they feel like they are laden with water(not heavy, no sounds of water in them).
Is this normal behavior? Is it something to worry about?
(I decline to identify the specific wheels at this time, as I am interested in learning more about the behavior of carbon fiber, not starting a flame war over a specific vendor.)
I dont think they should absorb water. However, if the carbon fibers/fabric is not completely enclosed in resin (i.e., plastic), then it is probably very possible for the fibers to try to suck in water via capillary action. Capillary action is very powerful and could even force apart some of the fibers, even those in resin.
Also, many wheels are hollow inside (like Zipps) for weight reasons. That makes for a lot of volume to trap water which doesn’t easily evaporate. And since the inside is not often visible to the maker (and never really to the buyer), the inside of carbon wheels is typically not well sealed which would of course cause the issue above.
Sounds like you may have a problem. Don’t ride your wheels in long rainy rides if you can. But I would contact the maker and see what they say about all of this.
I’ve experienced the white line where the brakes pads rubbed on my Lew’s during a rainy crit. The line wiped off with no lasting marks.
I’ve ridden these wheels several hundred miles since that event and they are perfectly fine.
It is possible to get water into the wheel from the spoke and or valve holes but I’d guess it would dry out rather quickly.
I don’t believe carbon is going to absorb much, if any, moisture. Let’s remember this is the same stuff that aircraft and spacecraft are built from. Catastrophic failures would occur in carbon sections if water made it’s way into the fibers during multiple heating/cooling cycles.
Resin coated wood has to be exposed to water over prolonged periods to even begin water intrusion and wood is pre-disposed to absorb moisture being a porous material.
Carbon is not porous and once coated with resin is likely more moisture proof than most anything you’ve encountered.