Just a point when figuring how much weight carrying capacity your truck has with P tires.
Fed regulations says this about P (passenger) tires on a truck; quote snipped for length
"When a passenger car tire is installed on a multipurpose passenger vehicle, truck, bus, or trailer, the tire's load rating shall be reduced by dividing by 1.10 before calculating the sum,"
Your current P285/50-20" tires may show a 2430 lb capacity. Now divide by 1.1 = 2209 lbs capacity. Keep them pumped to the max sidewall pressures when towing or carrying heavy loads. Then air down when the truck is empty.
Also diameters and capacities and tire weights can vary a bit between each tire maker for the same size tire.
