Tires on the back of a truck need proper air pressure to do two things.
1. ......carry the load without over heating at highway speeds.
2. and more air pressure to stop sway/handling issues....which means more psi to stiffen the sidewalls as a trailer can pushing the back of the tow vehicle around. P tires 44-51 psi is a very soft tire in the load carrying world of tires. I wouldn't run any P tire on the back of a truck carrying a load and pulling a trailer at anything less than max sidewall....especially those wide base /55-20" tires.
I've seen other 1/2 ton size vehicle owners go with those huge 20" E tires ....but come back in a few months and reported selling them and going with the std 17" OEM wheels and P265/70-17 tires.
