Older post, but just picked up my first Raptor. It was filled with 43 psi from the factory. I noticed the back tires probably have 3-4" of tread that aren't even touching the ground.
I chalk tested and wear monitored my stock tires and posted about it elsewhere. Low 30s is best, closer to 30 cold and 33 warm. This is optimized for street traction and wear, not mpg.