I have a pressure pro system. I have set my pressures at 65 on my class D tires. Here is what I have noticed. If the trailer is not in tow the pressure will rise with temperature (only a couple psi if tires are not in the sun). But when under tow for 10 miles or so I find my pressures do not very much (maybe 5 psi)from towing at 60 degrees ambient and 90 degrees ambient.
I have also noticed when under tow for at least 10 miles the tires on the sunny side will run about 1-2 psi greater than the tires on the shade side.
After under tow for 5-10 miles I watch for any tire pressure change.
I had a tire down a couple psi (still several psi from alarm) from the others. I stopped at the first chance where I could pullover safely and found I had picked up a 3/8 by two inch bolt in one of my 5th wheel tires. The TPMS saved me some grief that day.
