While the max pressures/load ratings on the sidewall are one way to start the most informative discussion on this topic that I've seen is back back a-ways in this forum.
Go back about 5 pages and look for Silvertwinkie's post on Tire Pressures. Scroll down to AccessMaster's reply. Very good info.
I've used this system for a while and found it works great. If I fill the tires on the GT to max it hops around and there is a greater chance of the wheels locking up during braking. Remember the contact patch is technically smaller and harder the more air pressure or lighter the load on the tires.
I've been in the car biz for 30 years and it's not uncommon to see cars come in from the quick lube places with 50 psi because the kids think more is better. Always aim for the pressures on the sticker or in the manual.