carbon frames

[syrus_82]

i am knew to cycling and i am wondering about carbon frames, i have red a bit about them and eac time i read something it contradicts what i read previously. like its responsiveness, some say not very and some say very, which one is it? does it depend on outside variables like the rider?
also the durability of carbon frames? there seems to be a debate over this, i am actually looking at a second hand giant cadex carbon bike. and am unsure about carbon frames due to all the debate.
any comments would be much appreciated
thanx

 

[rek]

I am by no means an expert on carbon, but from what I have heard and read there are a few problem hotspots:

• oxidisation/deterioration of the carbon fibre where it interfaces with a metal seatpost (I forget the proper chemical process that happens, but it's not a good one)
  
• gashes and imperfections in the weave of the material can considerably weaken the structure
  
• the epoxy holding the weaves together may start unbinding, causing strength problems

A lot of the subjective criteria of a bike such as feel, comfort, responsiveness, etc. can be attributed just as much (if not more) to tyres and frame geometry as it can to the frame's construction material.

I wouldn't hesitate to buy a modern carbon frame new (so long as I liked it of course!) I don't believe that carbon is still an experimental infant in terms of frame material -- by now, many manufacturers have had a lot of experience using it with proven designs, and just try to find a mid-high end bike these days that doesn't come with a carbon fork.

Used, however, I would be a lot more skeptical; it's quite difficult to detect small defects in a carbon frame caused through minor accidents, etc. And if there is a problem that is clearly visible, it makes failure a question of when, not if.

 

[Ralph Ray]

Did you buy that 56cm Giant Cadex that just sold on e-bay? Sweet looking bike. I love my"96 Time Helix Equipe HM. It's full carbon and I ride it almost everyday. No problems that I can detect and I do a once over on it all the time.

 

[xavier]

Many things you read online tend to be non sense.

Always look at the source. If anonymous - pay no attention.

People that want to be trusted and have nothing to hide will not have a problem posting real information (like me).

Online you have many begginers making themselves like they know it all. That is the beauty of online. Everyone can be whom they are not. With that said.

Please do not buy that frame online. It is very old, they were never very good and being used it may already be craked. Many people love Ebay because they can unload their junk there. I heard many already buying broken frames off Ebay. Usually because no warranty is provided or the frames are too old and companies do not honor warranty so people find a way to make money of it.

Carbon frames in anture last about 3-5 years of heavy abuse. With exceptions. Colnago type contruction to me is far more druable than the Trek style construction.

If you are looking for a carbon frame? Please buy one new froma legit source. This way you will have a warranty and not be worried about being ripped off.

 

[tafi]

Originally posted by syrus_82
i am knew to cycling and i am wondering about carbon frames, i have red a bit about them and eac time i read something it contradicts what i read previously. like its responsiveness, some say not very and some say very, which one is it? does it depend on outside variables like the rider?
also the durability of carbon frames? there seems to be a debate over this, i am actually looking at a second hand giant cadex carbon bike. and am unsure about carbon frames due to all the debate.
any comments would be much appreciated
thanx

The properties of carbon fibre are difficult to nail down. This is due largely to the fact that you can get whatever properties you want out of it by creating tubes or monocoque with different laying or braiding paterns. This can be a good thing as you can make tubes of any section you like (square, diamond, triangular you name it!) and can make a tube stiff against forces in one plane and absorbant to forces in another (eg a bike which is torsionally stiff can also be made vertically compliant and hence comfortable)
What is becoming clear is that carbon construction is only just coming into its own as manufacturers find the construction techniques needed to be able to get different properties at different parts of the frame. So I would not be looking at any frame more than a couple of years old.
The important thing to note is that the resin holds the fibres in the correct patern and any exposed firbres indicate a stuffed frame. Fibres thamselves cannot prevent crack propagation and once the resin is cracked through, the fibres will then pull out in tension. But provided th resin remians in tact, the fibres will not pull. i have not heard of carbon oxidising (unless it is set on fire!) but it is possible for water to get in under metal lugs. The use of full carbon frames these days have circumvented that problem.