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Discussion Starter · #1 ·
I've never had a carbon frame before, so I'm not so sure how carbon cracks develop or really look like...so, I've decided to ask for some expert opinions.

I haven't even taken the bike off-road yet...:(



I just don't want to bug my LBS unless its necessary....
 

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I am thinking seam.

Take it to the shop, point it out, and see what they say.

Take a couple more photos, and keep an eye on it for a while.

I think it is just a seam in the carbon, between joints, and is nothing to worry about. However, we are not in a position to touch the frame, so it is tough to tell.
 

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If it shows any sign of cracking on the seam it will need retirement, otherwise ride it and watch it closey, carbon frames are not perfict but a riser might not be a problem unless its growing/cracking but with carbon its a microscopic issue so stay on it!... good luck!
 

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Discussion Starter · #6 ·
damion said:
Take it to the shop, point it out, and see what they say.

Take a couple more photos, and keep an eye on it for a while.

I think it is just a seam in the carbon, between joints, and is nothing to worry about. However, we are not in a position to touch the frame, so it is tough to tell.
That sounds like a plan, I guess I'll just have my LBS take a look at it....
 

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My experience with carbon cracking is that it cracks creating an irregular edge, roughly around the warp and the fill (fiber weave) of the cloth. What your situation looks like is a yarn of fiber got moved out of place or accidentally stuck in the layup before the vacuum was drawn and the layup cured. It is kind of hard to tell from the photo. It could crack cleanly like that if there was a hard metal edge, like a reinforcing sleave, under the layup or if this is a seat stay and the seat post ends right at the point where the crack is. To get a crack like that on a composite layup usually takes a very hard edged load.

One way to be sure is to put a little spot of white hard paint (enamel) across the crack.If, after you ride, the crack cannot be seen through the paint, it is a blemish in the carbon layup.Be sure to use a hard enamel and let it dry well before riding.

I had a case where an 18" long crack in a carbon fiber mast did not show until several months later because the paint on the mast was more flexible than the carbon layup. Not until dirt got in the crack could I actually see it, and even then not until I lowered the mast. The crack was zig-zagged. Of all of the more than a dozen carbon failures I have seen, they all left a jagged edge. This included a failure involving an aluminum backing plate/block with a very straight edged load.
 

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Discussion Starter · #11 ·
RobLyman said:
My experience with carbon cracking is that it cracks creating an irregular edge, roughly around the warp and the fill (fiber weave) of the cloth. What your situation looks like is a yarn of fiber got moved out of place or accidentally stuck in the layup before the vacuum was drawn and the layup cured. It is kind of hard to tell from the photo. It could crack cleanly like that if there was a hard metal edge, like a reinforcing sleave, under the layup or if this is a seat stay and the seat post ends right at the point where the crack is. To get a crack like that on a composite layup usually takes a very hard edged load.

One way to be sure is to put a little spot of white hard paint (enamel) across the crack.If, after you ride, the crack cannot be seen through the paint, it is a blemish in the carbon layup.Be sure to use a hard enamel and let it dry well before riding.

I had a case where an 18" long crack in a carbon fiber mast did not show until several months later because the paint on the mast was more flexible than the carbon layup. Not until dirt got in the crack could I actually see it, and even then not until I lowered the mast. The crack was zig-zagged. Of all of the more than a dozen carbon failures I have seen, they all left a jagged edge. This included a failure involving an aluminum backing plate/block with a very straight edged load.
Great idea...thanks for that. I did take the frame to my LBS, and it was labeled as a 'hairline fracture", but they weren't sure wether it was superficial, or if it ran deeper. They sent some pictures to Giant for verification, so I'm expecting to hear from them. I haven't even taken the bike off-road, yet....err.
 

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It looks as though the carbon fabric got a small crease or lifted slightly from the surface of the mould surrounding the outside of the tube (if that is how they make them) :confused: ? That defect looks like epoxy which has moved in to fill the "void" produced by the creased fabric.

I remember making small honeycomb filled carbon panels during part of my training to become an aircraft mechanic. You really had to work the fabric very thoroughly and carefully to get good results. One person’s vacuum bag lost integrity and his panel ended up looking like a cross between a football and loaf of bread :eek: .

Anyhow, I am sure your LBS and Giant will find a resolution to the problem. Are carbon frames also covered by a lifetime warranty?
 
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