[quote=Jim Sears]The pressure marked on the tire is amount needed to get the maximum load bearing, not the normal operating pressure.
The tires on your pickup may say they are rated for 1874 lbs of load at 45 lbs pressure, but the recommended operating pressure is 30 lbs.
Are you sure about the 30 psi? I remember inflating my pickup and car tires to 30-32 psi and it was rated on the tire. GMC recommends tire inflation on my 2008 2500HD Duramax pickup at 60 front and 70 rear and the tires are rated at 75 psi. Once again it is rated on the tire.
Jim isn't really meaning any specific truck, only using those numbers as an example. However, there are real world example that have cold inflation pressure for a given tire size/load rating installed on the vehicle that are not the same as the maximum pressure listed on the sidewall. Example, '98 Chevrolet K1500 with a 245/75/16 LT E lead range. The tire is marked for 80 psi max, however, the vehicle spec is 45 psi cold. Same year, make, model truck with the P rated option tire, which is rated anywhere between 35 to 41 psi depending on brand, runs 35 psi. Obviously, using different size or load rating tires will change what pressure should be run.
Admittedly, there are times that the "engineers" get it wrong, and specify a pressure that is too low. remember the Ford Explorer?
On the not inflating over 40 psi part, that's for seating the tire. Once seated, it can be set to whatever the cold pressure for the tire should be.
