Originally Posted by BIG Laing
Depends on your application. Offloading? DD? Doubt your towing with 38x15.5?
Your wheel width will come into play here as well. You can run more psi with a wider wheel and not have the centers bow up as much than a narrow wheel at the same psi.
For daily driving, try running a chalk line across the tire and drive around the block. If all of the chalk is gone, note the psi, add more air, repeating the process until you see chalk on the outside shoulders of the tires. At this point, deflate to the last psi.
I ran my now discontinued Toyo 356/65-16s at the sidewall printed max of 50 psi and ended up running the centers out of them. Now that I am on BFG 315/75-16 ATs, I have found that about 40~45 psi is about the sweet spot for even wear. Like I told the monkeys at Discount Tire in Las Vegas after they tried (against my instructions not to) increasing my psi to the sidewall 50, "I didn't spend $1000 on those tires to ride on the center 6 inches of tread!!"