i got the same Goodyear Wrangler AT/D2 tires from sams, but i got the 255's... the tires say max psi is 44 and i have them right around 40 and have a pretty damn smooth ride, i wouldnt think goin down into the 30s would be such a great idea, may cause additional wear n tear. IMO i'd go with what the specs on the tires are and not the specs on the door, considering those aren't the same tires it comes with stock