Probably 30 to 32 psi, but I would just use 30 as a starting point. Ideally you want the contact patch to be just right and here is a good way to know if your tires are inflated properly: Get some sidewalk chalk...the kind the kids use. Now find a place where there is smooth concrete and long enough that you can drive far enough to make your tire go through at least 1 rotation. Draw a wide line (use the rear end of the chalk and not the pointed end) straight across one of your front tires from one side to the other (across the tread). Now drive far enough that your tires rotate at least once and then stop and go look at the chalk mark your tire made. If you see a nice straight line with chalk evenly distributed all the way across, you know that is the proper pressure and you can use it for both front tires. If you only see chalk in the center, you know you're overinflated. If you only see chalk on the sides, you're underinflated...and you may be able to tell the difference by seeing weak chalk and more generous chalk. In other words if you have 32 psi in that tire and you should have 30 psi, you may see the edges not as absent of chalk but showing only a faint bit of chalk where the center shows notably more. And then do the same test for your rear tires. Note: if you're actually using your AD as a pickup and not just driving around like a passenger car, then put something in your bed (2 or 3 people maybe) to do that test. You'll find you need more psi if you're hauling "stuff" around and only as much as the pressure used in your front tires if you aren't. Using a great deal more pressure in your rear tires when nothing is being hauled can cause your wheels to hop, bounce, etc...especially during hard braking and too much pressure will reduce the contact patch of your rear tires (which isn't good during braking nor for cornering...especially in rain).
