I am running 235/60R16s on my GV and have them at 28F / 27R. I get nice even wear from them at that pressure. When off roading, I reduce them to 17F / 14R for maximum traction.
My bro's Mazda B2500 has 31x10.5s (equivalent to a 265/70R16) and he runs those at 28F/ 26R. Any higher and the rear tyres start to wear out in the middle faster. The van handles pretty well at those pressures also, feels safe if you corner hard. When carrying heavy loads, we use as high as 42psi rear..
At one time, a tyre shop had pumped 45psi into all tyres on my bro's mazda (we bought new tyres) and the van rode horrible! The van felt like it was wandering all over the road and was difficult to keep it in a straight line. I had requested 28 all around..
The rental company for the pickups we use at work (Nissan Frontiers) had pumped 54F / 45R into the tyres on that van! Even with 235/75R15 tyres, it rode like pure crap..
So, do NOT trust anyone to inflate your tyres for you! Get yourself a good gauge, OR top up occasionally to maintain proper pressure.