Tech FAQ: Lennard Zinn on rotors and drilling frame drain holes

  • By Lennard Zinn
  • Published Oct. 25, 2011
  • Updated Oct. 11, 2012 at 4:52 PM EDT
AVID X0: Caliper/Rotor

Regarding drilling a drain hole in a carbon frame

Dear Lennard,

I have two questions regarding my Orbea Alma Carbon Frame. This year has been particularly rainy around my parts, and although I have tried to keep water out of the frame by using a piece of Lizard Skins neoprene chain stay protector around the slit in the upper part of the seat tube, I keep collecting up to an ounce of water inside the frame anyways. Having always owned metal frames in the past, I almost drilled a drain hole in the inferior part of the bottom bracket, but then I thought twice. Is this advisable on a carbon fiber frame? If it is, then what kind and size of drill bit should I use, carbide tip, metal? I certainly do not want to ruin the whole frame for the convenience of keeping water from collecting within.

The second question is, can I use nail polish to cover up clear coat damage from pebble impacts or do I risk damaging the frame’s integrity?

BTW, thanks to you and Morningstar I ride with true disc rotors.

— Manuel in Guatemala

Dear Manuel,

I would drill the hole, and any drill bit for metal will work; carbon is soft and requires no carbide tip or anything like that. I would drill a 1/8″ (3mm) hole straight under the center of the bottom bracket shell so it points straight down when the bike is standing up on its wheels.

I can’t imagine that there would be a significant weakening of the frame and cause for any concern, since that’s a low-stress area, but I suppose it’s possible it would void your warranty. If you’re still within the warranty period and want to ensure that the warranty is still valid, then I’d recommend you contact Orbea before drilling the hole.

And yes, you can use nail polish on your carbon frame. It does not have a solvent in it capable of dissolving your clear coat or damaging the laminate structure.


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Lennard Zinn

Lennard Zinn

Our longtime technical writer joined VeloNews in 1987. He is also a framebuilder, a former U.S. National Team rider, and author of many bicycle books, including Zinn and the Art of Mountain Bike Maintenance and Zinn and the Art of Road Bike Maintenance, as well as Zinn and the Art of Triathlon Bikes and Zinn's Cycling Primer: Maintenance Tips and Skill Building for Cyclists. He holds a Bachelor’s degree in physics from Colorado College. Readers can send brief technical questions to Ask LZ.

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