Different areas of the bicycle require different mixtures of fibres. The front of the bike, for example, experiences different forces on different planes than the bottom-bracket junction. It’s the same story for the downtube, the seat-tube, the drive-side chainstay (as opposed to the non-drive side chainstay), and so on. Because each of these locations demands a unique mixture of stiffness and strength to resist numerous unique load cases, we at Cervélo use location-specific laminations (layers of fibres at different angles) of high strength and high stiffness to achieve the desired performance.
Woven fibres are less stiff than the unidirectional fibres more commonly used in newer frames. Layers of unidirectional fibres, in which all the fibres in one layer are aligned in the same direction, let engineers 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 nothing but woven materials, 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 in what direction is critical to reducing weight, maintaining strength and producing a stiff bike that’s comfortable to ride. Composites let us place each fibre where it belongs; the challenge is that we have to place each fibre where it belongs!
The more critical the relationship between strength, stiffness and weight becomes, the greater the number of precisely placed and carefully chosen layers are required. This is where good engineering takes over from simple material choice. The key is that we need to select different types of fibres and carefully position them in the correct locations and orientations to best exploit their properties. Using advanced engineering software tools like Finite Element Analysis (FEA) and Ply Draping allows us to better understand exactly how each layer of carbon fibre is working and if it is being used properly. Of course, all of these tools would be worthless without in-house engineering knowledge of how they work, and testing that correlates simulated results with the real world.
This is one of the reasons a frame as light and stiff as the Cervélo Rca (pictured above) can only be made in our Project California facility, where we have the ability to precisely control ply size, shape and position tolerances. No wonder we were able to engineer many of the lightest frames — including the lightest frame, the Rca — according to 2013 testing by Germany’s Tour Magazin:
READ MORE ABOUT WEIGHT IN OUR ENGINEERING FIELD NOTES:
THE MYTH OF MODULUS: My wife’s bike has a decal on the top tube that reads “Super High Modulus,” so I am assuming this refers to the carbon fibre used. My Cervélo R5 doesn’t say anything about the material in any of the literature. Is my wife’s bike better than mine?
WEIGHT VS AERO: Which is faster: A more aerodynamic or a lighter bike?
COMPARING WEIGHT – INDUSTRY STANDARDS, PART 1: When it launched in 2013, Cervelo said the Rca was the world’s lightest road bike. Other companies make the same claim all the time. Is there an industry standard for comparing bike weight?