Sidewall pressure is the max pressure the tire can handle... the door tag, realistically, applied to OEM tire brand only... Other brands with the same rating should be ok with the door sticker... The inflation PSI is a function of the weight on the tire exerted from the vehicle. If you inflate to sidewall, more often than not the center of the tread will wear out first, as you will over inflate... What I did is to go on the michelin site, and looked at the engineering data for the OEM tires and backed into a design load for that tire at Ford's door sticker's inflation values... This will give you a weight that Ford enginners arrived at from their testing.. This weight can then be applied to other tires... I run LT lires on my trac because I tow a TT, and the stiffer sidewalls help a lot... When I tow, I inflate to 50 psi... The sidewall is 65 psi... When I don't tow, I drop the pressure to 30, per the engineering data.. If it ran the tires at 50 w/o a load on them, the ride is really harsh... JMHO