Nhra Rule Book Roll Bar. (a legal way to penetrate a roll bar tube). The nhra rule book states:
By adding diagonal door bars, this type of roll bar gives the vehicle a significant increase in rollover protection because the main hoop is supported both front and rear. We first considered aisi 4130, 1141& astm 106 b grade. A roll bar is required in any convertible running 13.49 seconds or quicker in the quarter mile, and in other cars beginning at 11.49.
Roll cages are mandatory for any car either running 10.99 or quicker or capable of exceeding 135 mph must be equipped with a roll cage.
Roll bars are mandatory in all cars running 11.49. All seat belt and shoulder harness installations must be mutually compatible, originally designed to be used In the 2011 nhra rulebook, e.t. Jr street rules section of nhra rulebook ;