The materials used in bicycle frames have evolved from the earliest chrome-molybdenum steel to aluminum alloys, and then to composite materials such as carbon fiber. Other materials include scandium alloys, magnesium alloys, and titanium alloys. Manufacturers continuously research new material formulations, improve tubing and structural design capabilities, and innovate processing technologies, all to make frames lighter, stronger, more comfortable, and more streamlined and aesthetically pleasing. Density is one of the key factors determining the weight of a bicycle frame; the lower the density, the lighter the frame can be. Chrome-molybdenum steel has a density of 7.9, aluminum alloys 2.6-2.9, titanium 4.5, titanium alloys 4.3-5.1, carbon fiber composites 1.6, and magnesium alloys 1.7. Thus, chrome-molybdenum steel has the highest density, while carbon fiber composites have the lowest. However, in addition to weight, tensile strength and elastic modulus must also be considered for the frame. Therefore, even with low density, insufficient strength is also undesirable.
Currently, the main materials used to manufacture bicycle frames include: steel, aluminum alloys, titanium alloys, magnesium alloys, scandium alloys, and carbon fiber. Frames commonly found on the market are primarily made of steel, aluminum alloys, titanium alloys, and carbon fiber. Scandium alloys and magnesium alloys are relatively new and less common materials.
