I needed a new set of 4.80 X 12 tires for my Lund trailer. So, I called the local guy that I buy tires from and he put them on this morning. The maximum pressure is listed on the side as 90 psi. I asked if he put 90 pounds in them., He said "Yes," but then went on to say that if my trailer "bounces" he would suggest lowering the pressure to 55-60 pounds. I asked him what he meant by "bounce." And, he said that when the trailer hits a bump in the road, does it bounce or does it bang pretty hard. My trailer does "bounce" in the sense that it really seems to "bang" hard when I hit a pot hole. So, he suggested lowing the tire pressure to soften the ride. I told him how sensitive the Marathons on my Ranger trailer are and that they'd over-heat and wear prematurely unless they are kept at 50 psi. He agreed, but said that the tire he installed are load rated far beyond the weight on my boat/trailer, so running 55-60 pounds would not create a problem. This guy has sold tire his whole life and I have bought lots and lots of tires from him. So, I have no reason to doubt his expertise. But, I thought I'd see what all of you thought.