Shock-absorbers are usually made of steel as it :

A shock absorber is a mechanical device designed to smooth out or damp shock impulse, and dissipate kinetic energy. Steel is an alloy made by combining iron and other elements, the most common of these being carbon. When carbon is used, its content in the steel is between 0.2% and 2.1% by weight, depending on the grade. Varying the amount of alloying elements and the form of their presence in the steel (solute elements, precipitated phase) controls qualities such as the higher elasticity, hardness, ductility, and tensile strength of the resulting steel.