The Michelin Tire Pressure Guide, available free on-line from Michelin, shows the appropriate air pressure based on Axle weight, and individual weight on each tire. It also lists several tire/rim sizes along with the required pressure to safely support the load. This save tires from premature failure and excessive tread wear. On my 2004 GMC Sierra 2500 4x4, Crew Cab with Duramax and Allison drivetrain, the pressures I use are quite a bit lower than the factory plackard pressures, because those pressures are fora vehicle that is at GVWR. Truck + Load +_ Trailer. The GMC is 80 FRoNT AND 80 REAR). I usually run 42 in the front and 35 in the rear because those pressures correspond to the actual weight I am carrying while EMPTY. I think the factory covers it's Tail by always displaying the highest pressures (for GVWR). Be mindful that you MUST run with Load Range E tires with these kinds of pressures. Mine happen to be 265/75-16 Cooper A/T 3's. Do yourself two favors; use Load Range E, and use the appropriate tire inflation psi based on that chart. Carry it with you in the truck, and you will always have correct pressure references for your Load.Too much pressure means excessive wear in the center tread. Too little pressure means excessive wear on outer treads, AND increased possibility of a blow out.