Road Cycling - Good Carbon? Bad Carbon?

I was at my LBS yesterday and me and one of the clearks got into a discussion about the infomus carbon frame. He has ridden alot of them but saying that some of them were % wood carbon" I am guessing that is a bad thing... I am just trying to figure out what is good carbon and what is bad.

Good carbon is probaly the ones he sells.

I agree with Shokhead. While there are certainly good, better and best carbon frames to be bought, I've never heard of a bad one, unless it came with a defect. Is it fair to assume that a $2100 frame is 3 times better than a $700 carbon frame? Probably not. Of course, brand names add a bunch to the equation.

What was he selling?

55/Rad

I have ridden the so called "wood" carbon. The old Trek had no road feel at all, and had the wood feel. I have had 5 carbon frames over the years and still ride one. The biggest difference in carbon is the way the frame is made. The glued up frames feel different from the one peice frames. Please don't buy one because your LBS tells it is the best. Ride a few and pick the one you like.

There are several, several types of carbon fibre on the market.
There are different grades, and different weaves with different tensil strengths.
CF is weighted by by the "k" size of the fiber. The designation "k" stands for 1,000 filaments, so a "1k" carbon fiber has 1,000 filaments. A "3k" carbon fiber has 3,000 filaments in it; a "6k" carbon fiber has 6,000 filaments in it, and so on...
Since each filament adds more strength and also weight to a "fiber", if you need more of weight or strength, just go up in fiber size, ie: A "3k" carbon fiber has 3-times the filament count of a "1k", 3-times the actual tensile strength, and 3-times the actual weight per given linear length of fibers. So, you would use a 3k carbon fiber instead of a 1k, if you found that a 1k fiber in a weave had too little strength.

There absolutely are differences in carbon constructions and molds.
There is uni-directional, and bi-directional (no jokes..now : **) weaves of CF
Knowing which bike company uses what grade, weave, and mold will nearly be impossible for sure. They can state whatever they want, but you will not know for certain.
If you think there is no difference in CF, you may be mistaken...

Here are just a few examples of the specs and composition of CF

Carbon Assay is the percentage of actual carbon content in fiber.
Denier is the textile term for mass per unit length. Denier is the wieght in grams per 9000 meters of material.

Denier Count is the width/Across direction fiber count.

Fiber Count is the lengthwise direction fiber count.

Interlaminar Shear Strength is the shear strength between layers of composite sheets or plys. Force needed to pull apart two or more layers.
Matrix Composite is the same definition as composite, but specifically intended as fiber and resin based composites.

Alot of CF is actually a mix of Silica or glass fibres, CSC. The glass fibre is used as a filling between layers of Carbon, this method of construction allows us to utilise the excellent strength and stiffness properties of Carbon fibre at the more critical outside surfaces of the part, whilst using the superior toughness and lower cost glass fibre as the centre to the sandwich. it is virtually impossible to tell the difference between pure CF and a mix. Then there is the forming processes...there are numerous methods for construction of carbon-fiber components including vacuum bagging, autoclave, and pre-preg materials, the vast majority of the carbon-fiber construction used in the consumer market is similar to the manufacturing wet lay-up method.

Yikes! There are so many variables to CF construction. It is doubtful that any product, from bikes to tennis racquets are pure CF. Ahhh, nothing is ever as simple as seems....eh?

Great info dc70 - very enlightening. For all the discussions ever had about the various steel tubing and aluminum alloys used in the making of a bike frame, I had never heard a word about the advantages or disadvantages to the many variables a carbon frame builder has at their disposal.

Any further information as it pertains to the various brands and their specifics would be terrific.

55/Rad

Thx for all the info i guess that helps clear some stuff up. I was lookin at a Look frame that is like 4 years old and my LBS wants 1k for it i dont know many peeps that ride look anyone have an input on them?

Great info dc70 - very enlightening. For all the discussions ever had about the various steel tubing and aluminum alloys used in the making of a bike frame, I had never heard a word about the advantages or disadvantages to the many variables a carbon frame builder has at their disposal.

Any further information as it pertains to the various brands and their specifics would be terrific.

55/Rad

Hey Rad,
When I was active in motorcycle roadracing, I did alot of research on CF.
It still is somewhat of a 'black art' and I think that is what alot of the bike companies
rely on, the fact that not too many consumers know the difference between all the
grades and variables of CF. The best guys to ask are small/lightweight kit plane builders.
These guys for the most part know the in's and out's of CF.

To find out exactly what each company utilizes in their construction process is
probably impossible. I doubt that information would given up, and if it was
is it really true. After the mold is formed and the piece is complete, there is no
way of knowing what type and grade of CF was used. I suspect that top of the line companies
probably use very good material. But you never know. Bicycles are not subject to heavy shear loads
like airplane wings, and formula type chassis's, so the grade doesn't have to be top quality.
Bicycles mainly have to support weight of the rider and the gyroscopic motion of the riders input
from the peddles to the wheels. Even in a crash, I doubt that the G loads get anywhere close to a race car or a airplane. There is no heavy accelertion/deceleration like in a racing machine, no extreme air pressure/temp changes subjected to airplanes.

The problem for us, is how do we really know what
we are getting for the money. You really don't unless the company is willing to
release their spec's of what they use. You know, everyone see's the words
'Carbon Fiber' and immediately assumes that it is a superior and top of the line product.
Fact is, some aluminum and Ti materials are better than low grades of CF.
As we 9consumers0 become more versed on CF, companies will be forced to
use the better CF and if not, either disclose what they use, or verify it.
I will pass along any other info I can dig up in my files.