First of all, my tires are Maxxis 16" E rated, 10-ply ST with about 10K miles. I check their cold pressure every morning that we are set to tow out and I put them right at the mfg recommended 80psi. Additionally, I have a TST monitor set and I watch for erratic pressure or temp swings.
Ideally, I like to tow at the tires E-rated 65mph. BUT...I do consider primary factors road condition and weather. While the tires were somewhat new, I found myself cruising at 70 to 75 while driving along flat, straight, newly re-paved interstates in dry clear weather with little or no other traffic. The truck and trailer handled the higher speed just fine though the mpg dropped from 11.5 down to 10mpg.
Lastly, my wheels are rated to handle 110psi and I am considering my next tire replacement will be to Sailun commercial truck tire S637 235/80R/16 G-rated @110psi. Need to confirm with HiSpec that the wheels are ok for High Pressure.
2016 Wildcat 295RSX - 2015 GMC 2500HD DblCab Duramax/Allison 4x4 Z71 6.6' Bed
Maxxis 16" E; Ride Rite AirBags w/AirLift 1 wireless compr; Adv.Folding 4 Cover
Andersen Ultimate II Aluminum 5erhitch on Reese Flipball w/Curt 4" offset ball
LCI Ground Control 3.0 4pt + 2pt Elec.Rear stabilizers; 3 Slidecovers; 10ft. Portabote
6000# Dexters; mor/Ryde CRE3000 w/HD Wetbolts; King Dish Tailgater; 5hp Outboard
Dual A/C; Furrion 48 Rear Camera; Champion 3100 Inverter w/Extended Run