Quality of carbon fibre

smaidment

I've been told that the quality of carbon fibre frames differs from manufacturer to manufacturer... but how can I find out how good the quality of the carbon fibre used to make the frame will be? Is there a grading/rating system that is used?

rake

there seems to be no standard measure. your best bet is to try and find out who makes it and see if they have any data. that said theres a hell of a lot more to it than the strength and modulus of the fibre, such as weather its woven or not, what directions its orientated on different parts of the bike, how much material is used in which parts of the bike, the shape and profile of different parts of the bike, the content of carbon fibres as a percentage with regard to the resin binder- theres an optimum ratio depending on the thickness and length of the filaments, thats another thing the fillament thickness is denoted in 'k' numbers ie 12k or 6k this is a measure of the cross section and equates to how many fibres can fit into a given area(cant remember the size) with finer fibres being more expensive to produce but can give higher strength because they can be distributed more evenly within the layup(if you used rope for a ridiculous example there would be a lot of rope in one spot and then a lot of resin in the gaps between). then there are different types of resin. its safe to say it a mine field and no one attribute will make or break it. from what i can discern your best bet are reviews from owners, and a reputable brand and or name to uphold.

smaidment

Goodness me! Thanks for this. It's obviously a lot more complicated than I initially thought!

It was the "k" numbers that I was thinking about... but I can't really find out what filament thicknesses are used by different brands. (Although I think planet-x and Ribble use 3k?)

cougie

I think that's too simplistic - you need to see how the frame has been made up too - check out the reviews - that will tell you how good the frame is to ride.

rake

i was thinking the same as you when i went to a carbon bike, being ever inquisitive i picked up a composite materials book in the library when i had a spare hour. its just a guess but i would say the expensive stuff is focused on weight saving rather than any great increase in strength as carbon fibres are pretty much the same density, so to get a lighter frame they cannot avoid using less material, which kind of cancels out some of the strength advantage. i think thats why there is not much info about, its so hard to gauge it.

nicensleazy

Depending on your budget, like most things!

Monty Dog

There are three components to a composite - the structural fibres, the resin and finally the application of a cosmetic finish. The 'K' often just refers to the cosmetic finish rather than the structural component - usually some sort of weave pattern to make it look 'woven' whereas a finished carbon composite is often just a dull grey. Finally and probably most critical is how they put it together - this is very process dependant and where going to a reputable maker is more important. Some of the numbers you see quoted are the designations of the fibres from the likes of Toray, available in low, medium and high modulus types:

http://www.toraycfa.com/index.htm