Book spec roll bar

[Talonmotorsport]

It depends on what size tubing you want the roll bar made from? I can currently do them in 42x2.5mm ERW which is more than strong enough considering what the chassis is made of and before some one says oh but the MSA - FIA blue book says this... I'm not making them for the 750 motor club race cars just road IVA passable cars.
I used to make NASA autograss specials from 32x2.5 ERW class 8,9,10 and they smack telegraph poles at 70mph+ and the whole chassis is made from it. The NASA rule book says that the roof of the chassis must 50mm from the top of the drivers helmet that is how strong the tubing is.

This link is what 32x2.5mm tubing copes with so 42x2.5mm is not going to be much different.

http://flickrhivemind.net/Tags/class8,crash/Interesting