Carbon fibre first emerged as a bike frame material at the 1986 Tour de France, when French manufacturer Look introduced the KG86 under Bernard Hainault and eventual race winner Greg Lomond.
The difference in the ride between a lugged steel frame and a carbon fibre-assuming, as in your case, that the two are top quality-is dramatically different. Steel tends to flex in a linear fashion-that means that adding another 25 pounds of leg and upper body pressure will deflect it exactly the same increment as the previous 20 pounds did. Metal has a very consistent, Omni-directional grain structure. A good steel frame is remarkably wonderful on a long ride, and encourages a good climbing rhythm. Carbon fibre composites flex according to the direction and number of fibres in the lay-ups, and react slightly differently according to the moulding pressure, temperature and other mould-related inconsistencies. Carbon fibre frames tend to flex easily for a slight distance and then tighten up in a more progressive manner. Aggressive climbers and sprinters like this feel.
For most of us who have been around a while, the image we have of carbon fibre is a sheet of woven fibres often seen through the clear coat of earlier bicycles. Although still around and sometimes used for their high strength, woven fibres are less stiff than the unidirectional fibres used more commonly in newer frames. Using layers of unidirectional fibres (all the fibres in one layer are aligned in the same direction) allows engineers to make the most of the high stiffness and light weight of carbon composites, however doing so requires much more detailed knowledge about composite materials. It is easier to design a frame using all woven material, but it will not be as stiff or light as one designed properly with unidirectional material. For frame engineering, knowing which fibres to place where and what directions to put them in is critical when attempting to reduce weight, maintain strength and still provide a stiff bike which is comfortable to bike ride.