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Discussion Starter · #1 ·
I wrecked my 2007 X0 med cage der a few months ago, so I decided to take a look at the "carbon" cage. I knew it wasn't complete carbon. Actually is very little and mostly plastic.

At the very top of this cutaway, there are 3 layers of carbon. You can see the 3 horizontal lines. It's inset in the channel of the plastic body. This carbon layer will even peel off. It is pretty hard - so I guess it provides some stiffness to the plastic.

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Here's a shot of the other side. You can see the smooth part of the plastic where the carbon has peeled off after the break. This part the carbon was very dry, I think a little too dry. Maybe that's why it didn't bond to the plastic very well.

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Now this is a 2007/06 model and I LOVE this derailleur - it's the best. I'm pretty sure they changed the materials in 09/10 as well.
 

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pedal pusher
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Sram has been faking the carbon stuff for years. The 9.0SL derailer and shifters are actually a "composite" material (i.e., plastic) with a cheesy looking faux carbon paint job. I remember getting mine back in '99 and thinking it would be so cool to have those carbon fiber parts, only to unpack them and see I'd been fooled. Great parts, and very light, but still.

Race Face also sort of faked carbon with their CarbonLP crankset. They actually had carbon fiber inside of the crank arms, but applied a thick decal to the outside of the crank arm for appearance sake, since we're apparently too stupid to accept them as carbon parts if we can't see the material.

I love Sram's shifters and derailers, but they're way too over-priced, and the "carbon" stuff is all for show.
 

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ups and downs
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That underlying material can still be carbon fiber reinforced plastic composite, but it doesn't look like the carbon fiber everyone expects. It's like the difference between the Easton Monkeylite bars with the CNT composite and Race Face or Ritchey carbon bars that have the 3K weave finish. In many carbon parts, including the under expensive DT Swiss XRC330 rims, the carbon weave is a finish and not structural. That's how DT Swiss knocked some weight off on the latest version of the carbon rims, they tossed the 3K weave finish on the unidirectional carbon rim.
 

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Additionally...

For consideration. Woven carbon is weaker and heavier than properly engineered structures made of unidirectional fibers (which is really a misnomer, fibers are often oriented in multiple directions too take advantage of carbon fibers tensile strength) which are not woven. Woven fiber cloth is sometimes as a surface for aesthetic reasons, and sometimes to proved a protective layer for the structure underneath.
Carbon fibers themselves offer the maximum strength to weight ration when they run as straight as possible, this why UD type construction is preferable: woven fiber cloth bends the fibers to make the weave. Layups using woven fiber cloth will also be heavier, as they have a higher resin to carbon ratio, as the resin must fill the gaps between fibers created by the bends in the weave.
As companies compete for lighter parts, we will see more and more UD type fiber layups, and eventually the woven carbon fiber look will be absent from high end bike frames and components.
 

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Discussion Starter · #5 ·
Just spray up some roving from the chopper gun and call it a day!! I used to watch the guys with the chopper gun standing inside a 40ft boat mold - ugly!! Then next door the some guys were laying up car parts with carbon prepreg on a vacuum mold. Night and day difference in the weight of those parts.

There are so many aspects of composite materials it boggles the mind.

The outer shell of the X0 shifters is a nice piece of carbon - very light. Its a weave - but it really doesn't need any strength. Just wish I had some nice carbon levers on my brakes.
 
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