Originally Posted by bigusnickus
Easy one: 4130 aka chrome-moly aka t45. It is what all race car roll cages and subframes are made out of. It has an infinite fatigue life (unlike aluminum) if properly designed and can be made nearly as lightweight as aluminum. Look up MSI's subframes. Common diameters are .75"-1.5" and wall thicknesses of 0.049"-0.095".
No, 4130 isn't what ALL race car roll cages and subframes are made out of. MOST of them are made out of DOM which stands for Drawn Over Mandrel for those of you who don't know. 4130 is used by racers that can AFFORD it.