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Bike Fork

Hello, I dropped the bike from standing and also had a front end collision later. The damage is from dropping the bike from standing because I can see the crack in a much older photo from after the collision. It has not changed much. However, I get worried it is suddenly going to bust on me and I am not very experienced with carbon fiber. Thanks. A bike shop has looked at it and ok'd it, but I am still concerned when going down hills.

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  • Unless the crack is clearly visible on the outside, it's hard to tell if there's one without an ultrasound scan. I very much doubt the bike shop had an US setup.
    – Klaster_1 Нет войне
    Commented Oct 29, 2020 at 6:01
  • Looks like it’s just paint damage and it doesn’t extend to the underlying carbon fibers. I’d remove the sticker to make sure there is no crack below it. Generally this shouldn’t be a sensitive/weak area.
    – Michael
    Commented Oct 29, 2020 at 8:17
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    It is so funny that the damage is right next to the label urging you to watch for damage! Reminds me of the "No moleste los signalos" signs in Baja California that had been clearly shot at.
    – Peter - Reinstate Monica
    Commented Oct 29, 2020 at 18:01
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    Would a bicycle manufacturer ship product that a fall from a stand would cause structural failure and instant death to its riders? Apart from the bad press, imagine the class action law suits. Any guesses how many bikes fall on the ground each day?
    – mattnz
    Commented Oct 29, 2020 at 20:10

3 Answers 3

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What is visible in the photo is a paint scratch. Letting the bike simply fall over will not structurally damage carbon fiber composite. People seem to think CFC is fragile but it’s really quite robust.

The fact that you had a collision is much more worrying. How hard? At what angle?

Hard, head-on collisions can certainly damage the frame or fork. The stresses are higher in the head tube or steerer area as the fork acts like a lever. Often damage to the head tube can occur but the fork is un- (or less) damaged.

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It looks like just a paint scrape to me. You should be ok. That said, some stranger over the Internet can’t make this judgment call for you - do you feel secure riding it?

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Strangers on the internet, no matter how knowledgeable or well intentioned, will not be able to diagnose internal damage to any part, no matter what it's made of.

Your local bike shop may be able to diagnose it.

For real confidence, find a local frame builder, preferably one who works in carbon fiber and pay to have it inspected. Yes, pay. He's a professional and makes her living this way, and you want quality advice, since it's your neck on the line. The advice in this answer I wrote a while ago, though addressing a steel frame and head-tube damage, applies equally to your potential fork damage.

See also this and this.

No, I'm not a frame builder, but I did know one when I was a kid. He spent many years in school and many, many years perfecting his craft. He took immense pride in his work and letting something out of his shop that he felt was dangerous was something he would not do. After finding that same attitude and level of pride with the builder who examined my frame after my wreck in college, I can't imagine a single frame builder who would do different.

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    My objection to this answer is that most frame builders will work with metal, and most of those will tend to just buy carbon forks from established vendors. Frame builders would generally lack imaging equipment designed for carbon (e.g. ultrasonic), so the answer you get might be no better than the answer at a bike store. There are some carbon builders who also do carbon repair (in my city, Appleman Bicycles, or Calfee more generally), as well as some people specializing in carbon repair (e.g. Ruckus Composites).
    – Weiwen Ng
    Commented Oct 29, 2020 at 18:13
  • Fair point, @WeiwenNg. However, I did specify "preferably one who works in carbon fiber". That may be more difficult to find.
    – FreeMan
    Commented Oct 29, 2020 at 18:15

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