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Old 04-29-07, 10:30 AM   #1
urbanknight
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How to inspect carbon fiber?

Long story short, last Fall my wheel exploded and lacerated the carbon fork on my 2001 Bianchi Veloce. Just to be safe, I bought a steel fork to ride on, but then noticed the crown is shorter than the one on my stock fork, causing the top tube to be about 1-2 cm lower in the front. This changed the geometry, requiring me to move the saddle back as far as possible, and the fit still doesn't seem right. I can seem to find any replacement fork that has 2cm from the brake hole to the steerer, so I need to know...

I have tapped every cm along the legs and the sound is uniform and solid. I have squeezed the dropouts towards each other and they only move a couple cm with no sound. The worst scratch is so shallow it can't be measured (less than .5mm) and is about 6mm long, so it looks like it's just scratches in the laminations. The fork did not take an impact during the crash, just got struck by the spokes and rim.

Is there anything else I can do to make sure this fork is sound? Or where to get such an elusive fork? As much as I would like a new frame, it's not in the budget.
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Old 04-29-07, 01:02 PM   #2
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The problem with CF is when it fails, it fails BIG and with no warning.....
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Old 04-29-07, 01:43 PM   #3
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magnaflux? don't know if it works on carbon or not but do a little research. here's a website http://www.magnaflux.com/index.asp
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Old 04-29-07, 07:40 PM   #4
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I can't find too much information on magnaflux, except that you have to request a quote on a machine, which leads me to believe that option would cost more than buying a new frame/fork. I need a solution that would cost me less than $100 if possible, because convincing my wife to let me spend even that much will be a miracle. I was hoping for one of these kinds of responses:

1) Here's how to check it. If it passes this test, you're PROBABLY fine.
2) Bianchi has a replacement program, and here's how to do it.
3) That fork was made by xxxxxxxx, so search for one of those.
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Old 04-29-07, 10:03 PM   #5
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what you need to do is measure your fork old forks crown to axle length in mm (center of axle to top of the crown where the crown race seats) and search for one that has a simular length or get back to us and see if someone can come up with a fork for you or try local LBS. Steel or alloy fork you might be able to find but a $100 carbon fork I would be abit leary of.
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Old 04-30-07, 01:36 PM   #6
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Quote:
Originally Posted by urbanknight
I have tapped every cm along the legs and the sound is uniform and solid. I have squeezed the dropouts towards each other and they only move a couple cm with no sound. The worst scratch is so shallow it can't be measured (less than .5mm) and is about 6mm long, so it looks like it's just scratches in the laminations. The fork did not take an impact during the crash, just got struck by the spokes and rim.

Is there anything else I can do to make sure this fork is sound? Or where to get such an elusive fork? As much as I would like a new frame, it's not in the budget.
There's no way you can gauge the strength of the fiber using the tap-test. That might tell you if it's just about ready to fail catastrophically, but not if it's compromised in a way that will show up down the line. Years ago when I was at a lab that worked with carbon composites, researchers used an ultrasonic imaging machine to reveal failures you couldn't tell were there. In other words, you will not be able to determine for yourself that the carbon is OK.

That said, a very shallow scratch as you describe probably shouldn't be able to kill the thing if you are absolutely sure it wasn't accompanied by blunt force trauma. Especially if it wasn't near a bend in the fork that might be subject to greater stresses.

Problem is you'll never be able to truly trust the thing, and it'll always be in the back of your mind. Now the more serious question is, what the hell did you do to your wheel?
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Old 04-30-07, 05:05 PM   #7
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Thanks Mr.Underbridge. My front wheel was built with Revolution spokes, and I didn't know the thinner guage would read differently for the tension, so I overtensioned the spokes which lead to a rim failure. When the rim failed, it snapped the rim right in half and I went over the bars.

You're right, I probably won't be able to trust it. The sheared part of the rim most likely struck the fork, which would be a blunt force of some sort. I was just hoping that if the impact was enough to damage something, there would be a telltale sign like a hollow sound or something. I can't seem to find a fork with the same specs, and Bianchi doesn't return emails. I guess I'm relegated to riding it with the improperly sized steel for for now, and hopefully just deal with the altered geometry.
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Old 04-30-07, 07:13 PM   #8
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Unfortunately that is one of the problems with CF, there's just no way for a person at home to check it and guarntee it's safety. The only thing you can do is to check for scratches that are deeper then just paint, gouges or other surface problems; check to see if the frame lost rigidity by load stressing it by placing one foot on a pedal at the 6:00 position and your other foot on the floor, lean the bike away from you and then put force on the pedal to flex the frame; when doing this procedure and while riding it listen for unusual sounds like cracking, popping or creaking. Is there problems with shifting or braking or handling or ride quality; this is all an indication of a loss of rigidity. Then also check the frame for delamanation which consist of loose fibers or splintering effect; drag a cotton cloth over the frame in all directions and see if it snags on anything where there shouldn't be anything to snag.

But if in doubt take it back to the dealer, CF products will fail suddenly without warning which could cause severe injury and maybe even death to the rider if they land unluckly.
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Old 04-30-07, 07:47 PM   #9
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^ Very good information for checking out frames (some of that I found on the Trek website), but only my fork is carbon. The frame is steel, but doesn't seem to fit any other fork than the carbon one it came with. I'd love to just get a new frame instead since it got scratched up in the crash as well (Serotta Ti since we're dreaming here), but just don't have the cash right now... or for the next few years.
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