I just caught up on this one. for me no matter what tire I am using if it is in a trailer aplication I use max PSI. two reasons which have been brought up, trailer tires are subjected more to sidewall flexing and scubbing, and the second better fuel milage, I guess there is a third. less of a chance of excessive internal heat generated. now on my truck if I know I am not going to be towing or hauling anything I will lower my rear tires for about 60 PSI. if I go by weight I could go to 40 psi but the tire company said not to go under 55 on them so I figured 60 was a nice round number. but if I am hauling I don't play around with 70 or 75 psi anymore just fill them to 80psi and have a bit of a saftey cushion.
Steve
