it depends on your front end weight, and weather you have a front wing. It's all about down force with the wing, it adds front end weight.
Mostly with out a wing we run 35-40 lbs of pressure, and up to 80lbs with a good size wing. Big show TF run as much as 100lbs with their wing that adds 2500 lbs of down force.
Simple right ? BTW owheavy are your alloy wheels and tires ? Wire spoke wheels and tires can weight as little as 7 1/2 lbs each if your alloy wheels & tires weigh 35+ lbs , it's like adding over 200 lbs of static weight, because one pound of rotating weight is equal to 10 lbs of static weight. And the thought is if you take 100 lbs off your car you will pick-up a tenth.
I hope this helps , not confuse,
Jon
