Here's the scenario. I inflate my tires to 35 with my truck box empty. Then I put (wildly made up number) say, 3000lbs of steel plates in the box. Will the PSI in my tires, especially the rear, change because of the added weight?

I'm wondering because I was recently popped a balloon by squeezing it It seemed that this was only possible if the pressure over surface area increased as I squeezed (simulates added weight, right?).

So whaddya think?