A good illustration of this is the difference between an elastic band and a toothpick. The elastic band will easily bend and is difficult to break (low modulus), while a toothpick won’t bend very much before it snaps (high modulus). Just remember that the higher the modulus number (300 to 1000), the stiffer and therefore more brittle and ultimately weaker, carbon fiber is.
Many bike manufacturers have fallen into the trap of playing the “my modulus is better than your modulus” game by using the terms high modulus and even ultra-high modulus. This sounds impressive but is just marketing gibberish. Different carbon fiber manufacturers and even the Japan Carbon Fiber Manufacturers Association (now part of the JCFA) use a variety of terms to classify carbon fiber modulus. There can be three to five levels, including low to ultra-high and standard to high.
The important thing is to know is that 700 modulus carbon fiber is the standard for producing high-end bicycle frames. 800 modulus carbon fiber is too stiff and brittle to be used to make an entire bike frame, but it can be used sparingly when a manufacturer wants to fortify certain high-stress areas of the frame. This is what Gerard Cycles does as an integral part of our G-Spec CarbonProcess. But it’s not at all possible to use 1000 modulus carbon fiber, as it’s extremely brittle, very expensive, and is usually reserved for use by the aerospace industry. Any bicycle frame manufacturer that says it uses 1000 modulus carbon fiber is misrepresenting its products.
The important thing is to know is that 700 modulus carbon fiber is the standard for producing high-end bicycle frames.