Bikes are not all metal. Remember that a great bike is built on proper balancing of the framework to be sturdy and a great contraption on wheels. Tensegrity is a word coined by Buckminster Fuller to describe structures where strength and integrity are achieved by balancing members under compression, with other that are in tension.

In creating a bike frame where most of the members are under tension, Romanian designer Ionut Predescu’s Wire Bike replaces most of the tubing with high strength carbon fiber and Kevlar cables, saving lots of weight in the process.

(Source) Yanko