IIRC correctly, it's 37 on the Rubicons (at least the 4xe).36psi is actually what is recommended. Dealers keep them anywhere from 38-42psi to make the gas numbers look a little better for people who don’t know any better. Around 32psi is what quite a few people end up with
Even at that, it's more than enough capacity:
2,189x4= 8,756 lbs, compared to a GVWR of 6,400 lbs.