70 in the rear with an empty truck? Wow, that thing must ride like a stagecoach and wear the center of the tire quickly. 35 in the rear of my old Dodge empty and the tires wore dead even across the tread. 55 in the front with the Cummins and they wore perfect. I got 80k out of multiple sets of Michelin LTX tires. Definitely air up when loaded but empty you don't need to go crazy.
2013 Rockwood 2109S
2010 Dodge Ram 1500 Crew Cab 4x4 Hemi