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Is this a stress crack?

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Is this a stress crack?

Old 04-18-15, 10:48 PM
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Yo Spiff
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Is this a stress crack?

Found this scratch or crack near the crown of the carbon fork of my 2000 Bianchi Veloce. My better judgement tell me "don't ride this. Get the fork replaced". But I don't know what I am really looking at.

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Old 04-18-15, 11:06 PM
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Looks dangerous. Don't ride until you find replacement. Such crack in paint layer indicates the zone underneath it went through a huge amount of stress, the fork could have lost its integrity. You could hit a pothole and that may caused the crack to appear. By riding further continuous micro-strikes may cause the crack to progress.

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Old 04-18-15, 11:23 PM
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With the front wheel removed try and pull the fork dropouts apart manually while observing the hairline. Does the hairline expand any when doing so? Did it get longer? Does it creak or make noise? What if you manually press on the hairline itself with fingers?

I believe the fork on this model has an aluminum steerer tube, no? This would be were the carbon weave starts meeting the aluminum crown.

It could be just a paint crack, but if you are unsure, do not risk it. Any reputable shop should help point you in the right direction. Perhaps most importantly, if it seems to get bigger, do not ride it at all (really shouldn't ride it anyway if you are unsure).
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Old 04-18-15, 11:28 PM
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Yes, no or maybe. It is a stress crack, but it's right about where blades and crowns are joined. It isn't rare to see some flex there and a crack form in the surface layer that doesn't affect the structure itself.

I tend to be conservative where forks are concerned since the consequences of a structure failure there are about as bad as possible. But there's a very good chance it could be OK. It would take a more detailed examination to make a reasonable assessment. So either have someone competent look at it, or err to he side of safety by replacing it.
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Old 04-19-15, 12:16 AM
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It could be a crack, but without a hands on look, it's hard to tell. As some suggested, you could try and spread the fork to see if it expands. Typically, with carbon, you can tap with a small metal tool and it will have a distinctively dull sound at the spot of a crack, but that might be harder to tell at the crown of a fork that tends to be pretty thick in general.

One possibility is that a piece of debris could have gotten caught in the spokes and struck the fork at that spot, which may or may not cause a crack, but you probably would have heard such a load event. Possibly, it could just be a really deep scratch from something getting caught in the spokes and scraping across.
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Old 04-19-15, 03:49 AM
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If I understand the gist of this problem here, we have a dilemma whether this is a scratch or a crack. Would it not be simple enough to find out by means of a very thin blade jammed into the crack - or scratch, as it may be? To me this seems like a very simple experiment to do, but I have easy access to scalpels. However, a razor blade will do just as well in a pinch. I also have a hand-held microscope with LED light which is suitable for inspection of this feature.
I should add that, were this my fork I would not hesitate to scratch away the paint from a small portion of the feature in order to ascertain whether it's a crack.
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Old 04-19-15, 09:16 AM
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Thanks for the advice. I'll take it to have a professional look at it.
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Old 04-19-15, 09:21 AM
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May be where the Aluminum fork crown core ends and the Carbon blade end begins..

Got 10+ years of use Out Of It .... buy a New Fork.
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Old 04-19-15, 10:15 AM
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The two easiest NDIs of composites are a tap test and shining a strong light on the suspected crack.

Tap with a nickle lightly and see if there is any discernible difference in the sound from the other side. Cracks go thunk, OK goes click.

If you shine a light on it, a crack will not reflect light out of the bottom of the crack. A scratch will.

Also you can flex it gently and see if it widens.

From the photo, it looks like a scratch, maybe something picked up by your wheel briefly like a small branch.
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