Ford F250/F350 Michelin LT275/70R18 LTX AT2
Stick with vehicle manufacturer range. We've had two tire engineers contribute on this forum, and both note serious liability concern, thus, testing, to establish limits. Tire pressure charts are not the guideline.
Weigh the rig. Get individual wheel position readings. Use axle end with highest loading for reference.
I'd move around plus or minus 5-psi from there on my one ton.
I believe it a real mistake to overinflate, which many do (to more closely simulate the response of an empty, solo vehicle versus one which is loaded AND towing). Steering will be different, and it takes time to adjust to that; both degree and duration.
Pickups need all the help they can get in maintaining the largest tire contact patch.
So long as pressure rise from dead cold is about 7-8% (but no more), one then knows the lower inflation number.
For purposes of experiment, take the loaded weight of the TV with loaded trailer attached and duplicate that, front and rear, for solo driving. Unconscious habits of decades standing deserve reexamination. I'll state that there is more problem here than is understood, as braking distances are multiplied, sometimes vastly, and steering/braking feels a good bit different.
13-weeks of driving solo in this manner will help establish new habits.
For the most part I don't drive any differently solo versus towing (in main, how far I wind out the transmission shifts). "Keeping up" with traffic is the main habit to break. Followed by speed into curves and turns.
On a one ton they should last well over 70k miles for a premium road tire. This is dictated by driver habits. Pressures will fall into place pretty easily once the use of a loaded vehicle is part of the regular repertoire.
Best possible trailer braking performance is also ignored. Full amperage to each wheel is a minimum.
1990 35' Silver Streak Sterling
; 9k GVWR.
2004 DODGE Cummins 305/555; 6-manual; 9k GVWR.
Hensley Arrow. 10-cpm solo, 18-cpm towing
Sold: Silver Streak Model 3411