I have mounted a new set of carbon rims on my bike. To be precise, it's a pair of Mavic Cosmic SL. And I've noticed that they have some little "holes" along the profile.

What are they used for? Since I'm planning to attach the stickers on them, I like to know if I can cover these holes with them, or I have to adjust the stickers in a way to let these holes free.

Sorry if it is a silly question, and thanks for any help.

enter image description here

  • 1
    Personally, I'd leave the stickers off entirely. I like the cleaner appearance. but mounting three stickers with three holes shouldn't be hard -- put each sticker between two holes?
    – arne
    Commented Aug 19, 2022 at 9:03
  • 1
    @arne, I agree with you: in theory it is not that hard, but the fact is that those tyres already have little Mavic stickers on them (they are not visible in that portion in the picture), and I already have to take them into account. So, a lot of little details that overlap with the future stickers, and I need to cover the lowest amount of them :)
    – Andrea
    Commented Aug 19, 2022 at 9:28

2 Answers 2


They are drain holes to let water out.

Light bicycle go into slightly more detail on their webpage: https://www.lightbicycle.com/newsletter/Holes-On-Your-Carbon-Fiber-Rims.html

  • Thank you for your answer. I've noticed that my rims have three of them for each side. So, basically, I imagine it is better to not cover them with stickers, but it won't be a big thing if one out of three would be covered (it's a bit difficult to place threes stickers by each side - as Cosmic standard - by leaving all of them uncovered).
    – Andrea
    Commented Aug 18, 2022 at 9:28
  • 5
    @Andrea just poke a little hole through the sticker in the relevant spot after installing it.
    – MaplePanda
    Commented Aug 18, 2022 at 9:30
  • 1
    Minor detail: I don’t think these drain holes are common, but these rims have a non-structural carbon fairing with entry holes for the spokes. So, the drain holes do actually help here. This is a relatively rare type of rim.
    – Weiwen Ng
    Commented Aug 18, 2022 at 15:45
  • @WeiwenNg I would beg to differ as to your claim that these holes are not common. My Roval's have them and I have seen them in other brands as well. They may not be universal, but I believe they are more common than you imply. I could be mistaken however...
    – Ted Hohl
    Commented Aug 18, 2022 at 19:42
  • @TedHohl fair enough, perhaps I should rephrase to they aren’t universal on structural carbon rims (which is just about all carbon rims)
    – Weiwen Ng
    Commented Aug 19, 2022 at 12:38

The hole also acts as a pressure release valve. In the event of air leaking from the rim bed through the tape or valve, it is important that the pressure does not build up inside the rim. If that happens the rim will explode! Enve has had that problem and has therefor invented a new special valve due to several explosions.

  • This sounds implausible. Looking at the picture you can clearly see that the spoke holes could do that job easily.
    – Burki
    Commented Jun 11 at 13:32

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