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Question on carbon frame integrity(7 posts)

Question on carbon frame integrityMcAndrus
May 22, 2002 6:59 AM
On eBay there's a Kestrel 200CSi for auction. It's my size and looks like it could be a bargain. The lister admits there is a dent in the seat tube. It's difficult to tell from the picture how large the dent is but I'm guessing 2cm around.

I fully understand that a dangerous frame is not a bargain. The question is, does anyone think this compromises the frame's integrity enough to avoid riding it?

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=1830846221&r=0&t=0&showTutorial=0&ed=1022430054&indexURL=0&rd=1
I'd ask the seller for a better pictureDave Hickey
May 22, 2002 7:14 AM
You can't dent carbon fiber. It's hard to tell from the picture how bad it is.
I saw the dimple in the picture, and I'm wondering howPaul
May 22, 2002 9:15 AM
you do that with carbon? Why is this guy selling the bike? People and E-bay shouldn't allow damaged goods to be sold. Like that cracked Colnago awhile back on E-bay. Someone should be liable. If you buy a known defective car from a dealership, they are criminally liable for that sale. Seems like these guys get away with breaking the law under the guise of an auction.

Personnally, I wouldn't buy it for shipping. Biking is dangerous enough without wondering during a descent whether the bike will hold together. Every metal/carbon will fatigue over a period of time, and this guy doesn't know the mileage on the bike. Your life is worth more then 100.00.
re: Question on carbon frame integritytarwheel
May 22, 2002 10:01 AM
I would contact Kestrel and see what they say. My guess would be that it would be more expensive to fix than what it's worth. I bought a used steel Merckx frame on eBay a few weeks ago and it turned out to be damaged. The seller refunded my money and told me to keep the frame. After contacting a number of frame shops and painters, it looks like it would cost anywhere from $400 to $700 to have the frame repaired and repainted -- when you factor in the cost of shipping, new decals, etc. Steel is supposed to be much easier to fix than other materials, so I can only imagine how expensive it would be to fix a carbon frame. Even though the Kestrel is nude carbon, they would still have to replace the entire seat tube, add new decals and clear coat.
Carbon doesn't dent, it breaks... I thinkPdxMark
May 22, 2002 11:09 AM
A dent in a malleable material, like steel, means that a region of the material has been displaced from it's original shape within the "elastic" limits of the material. I don't know which particular material property is at play, but my understanding is that carbon fiber matrix is not malleable once the resin solidifies. This would mean that in carbon a "dent" really means that at least some resin has broken away and that even some carbon fibre has been broken.

If this is right, it's not a dent, but rather a broken frame even if the break does not go all the way through the carbon.
This analysis is correctKerry
May 22, 2002 4:54 PM
This frame is not dented, it is fractured. The epoxy matrix has failed, and I'm sure a bunch of fibers are broken/pulled out of the epoxy. It's a goner.
re: Question on carbon frame integritySoultrain
May 22, 2002 10:30 PM
Had a friend that damaged his kestrel 200ems and had the factory repair it for him, fairly similar damage to the one that you are describing, however I think that the particular circumstances of the damage would detirmine the repairability of this specific frame. Oh, and the repair cost him $900 dollars. That's a lot of green.