very informative Trailsy !!!

whats reynolds 531 about then? (i think its 531)

actually i looked it up:-

The approximate alloying composition of 531 tubing is 1.5% Mn, 0.25% Mo, 0.35% C, and is similar to the old British BS970 En 16/18 steel. Its mechanical properties and response to heat-treatment are broadly similar to the AISI 4130 standard alloy steel, also used for bicycle frames, among other applications. This material was used to form the front subframes on the famous Jaguar E-Type car of the 1960s.

Reynolds 531 is now only available to special order, but in the past was used by many bicycle manufacturers for their racing cycles.

Nearest Available Stock material is BS4t45 to Bs4T100 (T45)

4130 was the material all top end bmx's were made of up until maybe five years ago, lots of use of butted tubes and heat treating today though...quite a coincidence those two numbers popped up :)

think we should use it for the fad club name.... "ESC 4130"