YOU NEVER NEVER NEVER NEVER NEVER NEVER EVER run what the tire says on the sidewall unless you ALWAYS run FULLY LOADED to the tire's maximum capacity.
For these 225/75-16s ThunderbirdJunkie would recommend 35-38 psi.
Anything more you are sacrificing traction and tire life.
When I was young and foolish and had my first car I remember making the same mistake of running at the tire's maximum tire pressure.
I know of the chalk trick but I've never gotten around to trying it. Even though they aren't the stock tires I run my LT245/75R16 AT's at 33 PSI. They haven't yet shown any signs of bad tread wear and handle well.
While on the trails with my Liberty I don't air down simply because I need every inch of ground clearance I can get. Plus it saves me the bother of airing down & up. I have a YJ too with 33" tall tires and lots of ground clearance that I've aired down as low as 10 PSI. Of course I wouldn't drive the YJ at highway speeds at that pressure. The tire's sidewalls would blow out.