Differences in bicycle frame materials

2003 Orbea Mitis, made from Aluminum with an Easton EC90 CNT Composite Carbon Fiber fork. My previous frame.

The diamond bicycle is a design that has been relatively unchanged for over a hundred years. The basic shape however, can be created in many different materials. As technology has evolved, we have seen more materials come about, including the introduction of aluminium, titanium, carbon fiber and other composites for frame construction as opposed to the traditional steel tube set. Even steel tubing has seen technological advancements as new steel tubing is relatively light compared to those created even twenty years ago. Here is a breakdown of a few of the most common materials used to make bicycles.

Steel
    The most widely used material for bicycles, steel comes in many different flavors. Yet the one thing that is synonymous with steel is that it's compliant; meaning that it absorbs and dampens much of the harshness and imperfections of the road. Being one of the heavier materials for bicycle manufacturing, steel is not widely used for racing anymore because it lacks the stiffness of other materials (which translates directly into a loss of power from the legs to the wheel).

    However, steel is still coveted by many as a great comfortable, durable bicycle for touring, commuting, and city riding. Because of this, small manufactures have actually been custom building bicycles out of steel to cater to a boutique crowd of individuals who find the classic thin-tubed bike to be the most elegant. Manufactures like Cielo by Chris King, Yamaguchi, Vanilla Bicycles and others are great examples of bespoke steel bicycles.


Aluminium
    Aluminium is perhaps one of the most misunderstood materials for bicycles. Most any bike that can be found at department stores is usually made of low grade aluminium which translates into a very heavy bicycle with unsightly welds. Yet aluminium was the all the craze back in the late 90s and early 2000s before carbon fiber was widely adopted for high end bicycles. Aluminum tubing is generally oversized and very thin, to make a generally light bicycle is also very stiff. The ride quality on aluminum is commonly understood as being quite harsh, given that there is no compliance due to the rigidity of the oversized tubing. Aluminum alloys like Scandium were also introduced as even lighter alternatives. High end aluminum bikes use new technology, including revisions to bicycle geometry, to make the ride not as harsh while maximizing the stiffness.

    Aluminum has predominately been replaced on the flagship models of all brands by carbon fiber composites. Because of this, aluminum bikes have become the entry level bicycles which allow for beginner cyclists to get on a fast machine without having to spend very much money. Individuals can spend as little as a thousand dollars to get onto an aluminum bicycle nowadays that is good enough to compete with composite bicycles that are easily five times as expensive.


Carbon Fiber
    Making a bicycle out of what can be categorized as plastic is something that many people have a hard time understanding. However, the technology in composite materials over the last ten years has spiraled carbon fiber as the leading material to build high end bicycles with. Not only is it stiffer than aluminum, but when carbon fiber is laid in the correct direction and used in the right way, it creates a bike that is laterally stiff but vertically compliant. This gives a very stiff frame that does not flex side to side, but does absorb the up and down motion which gives aluminum bicycles a very harsh ride. The introduction of what is a high modulus carbon fiber, as well as different weavings such as unidirectional fibers and prepreg layers has made carbon lighter and stiffer than about any other material out there. Carbon fiber is the material of choice for every single bicycle frame in the 2012 Tour de France; this  alone is a testament to how much this material has advanced in the last few years.