The main materials used to manufacture bicycle frames include: steel, aluminum alloy, titanium alloy, magnesium alloy, scandium alloy, carbon fiber, etc. Generally, frames available on the market are made of steel, aluminum alloy, titanium alloy, and carbon fiber. Scandium alloy and magnesium alloy are relatively new and less common materials.
To understand the properties of these materials, it's necessary to know some basic concepts and parameters:
1. Strength. Imagine a weight hanging on the other end of a metal rod, heavy enough to cause permanent deformation. That is, when the weight is removed, the metal rod remains bent and cannot fully return to its original shape; this is called yield. The force required to achieve yield varies depending on the material; this is called strength. Strength is related to frame durability but not riding quality. Strength is determined by the material's yield strength. Yield strength is significantly affected by the quality of the frame tubing, heat treatment process, and alloy composition (for some brands).
2. Stiffness (or rigidity) can be described as follows: Imagine a metal rod with one end fixed to a clamp. A weight is applied to the other end, causing the rod to temporarily bend. When the weight is removed, the rod immediately returns to its original shape. The same weight applied to different materials will produce different degrees of bending; this is stiffness. Stiffness affects the riding quality of a bicycle frame because the frame is most susceptible to deformation during normal riding. Stiffness is determined by the material's modulus of elasticity, and importantly, the modulus of elasticity is independent of the metal's quality and the composition of its alloys. For example, all types of steel have essentially the same modulus of elasticity.
