What do the H bars do to the chassis and are they worth while?

RR

 

Not too sure what you mean as 'H' bars.
Assuming you mean lower front brace, then they do little if you suspension is stock in other areas.
If the suspension is well modiied, then the extra stiffness is always welcome on the chassis.

Graham

 

I found on GC8 that the lower control arm support aided quite a bit, particularly in braking where the front is more consistant and fair less prone to "wonder" under hard brakes. It also sturdy's up the front end (more apparant when using R spec competition slicks) under corner loads and allows a much more consistant feel through it.

However I must add that I have quote a bit of bracing on the car with relatively tight spring and damper package.