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  1. #1
    Senior Member
    Join Date
    Dec 2006
    Location
    Columbus, Ohio
    My Bikes
    Serotta Colorado III Track (Renyolds Ouzo Pro Aero Fork, Dura-Ace to Mavic CXP-14 wheels, Sugino crank, Thomson and 3T the rest), Steelman Cyclocross (Campy Record 10, Deda Newton & Thomson stuff)
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    Carbon Steerer Damage

    I recently built up a new bike with a Renyolds Ouzo Pro fork with a carbon steerer, and decided to use a cheap Truvativ stem until I got the fit figured out. I started out with 20mm of spacers and the stem mounted up, and then finding the bars too high I flipped the stem over and rode around the block a few times. The headset was a bit off, and I still wanted the bars a bit lower so I went to adjust the compression cap and move some spacers around and noticed that when I had flipped the stem it had caused the inside machining of the stem to fall right near the top of where the steerer had been cut, causing two areas where the carbon had turned white from the stem pushing on it.

    The carbon does not appear cracked or broken, and I put a bit of super glue over the edge of the white area in the mean time, but I was going to run the new stem (Thomson this time) stem lower down on the steerer tube anyway, so none of the new stem will clamp over any of the white area.

    Am I best off cutting off this 10-12mm section off the top of the steerer, or leaving it as is and putting a spacer over the stem? If I cut off all of the damaged area I would still have more than enough room to run the stem as I want.

    I know carbon has a tendency to propagate cracks and such, but I'm also wary of cutting the steerer as I have never dealt with that before.

    I guess the moral of the story is to be more observant of how the stem clamps to the steerer.

  2. #2
    Senior Member
    Join Date
    Jun 2008
    Location
    Cambridge, MA
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    Can you post a picture? It is important to determine if the carbon was damaged in any way. This is difficult to do from your description. It sounds like just the resin may have been scratched.
    If you decide to cut the carbon, make sure to wear a mask as it is supposedly very unhealthy to breath in the dust. Also you should wear gloves as carbon splinters easily.

  3. #3
    Senior Member
    Join Date
    Jun 2008
    Location
    Kent, WA
    My Bikes
    '07 Specialized Tarmac Pro
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    Actually, CF doesn't propagate cracks, almost at all. Metal does, not CF. If you're planning on clamping completely below the spot that looks damaged you're probably fine. You can cut it off or just use the spacers above it. A picture would certainly help though.

    Just found this link that might help you.
    http://bike-manual.com/brands/bontra...bon_fiber.html

    Do the "tap test" they have described, (video included on the site) if the tap test sounds good in the area you will be using for the new clamp, you should be fine.

  4. #4
    messenger
    Join Date
    Aug 2008
    Location
    WLA
    My Bikes
    pinarellos and a colnago
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    599
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    untreated carbon is like a sponge--- treat the area--- the less you cut the better--- a picture helps--- don't use any kind of super glue or wd or chap stick or whatever--- if you cut carbon--- wear a mask cut it all the way and use sharp tools----- it sounds like you just disrupted the top coat seal.....

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