I ran 31" on stock rims for years. Worked fine. I like a little more sidewall for the type of wheel'n we do in AZ. You can air down a little more.
The other thing is check prices. The same tire may have a big difference in cost depeding on the rim size.
82 Cherokee WT - SOA/SF/agr box/Borgeson ujoint steering shaft/401/performer/holley TA/HEI/BeCool/727/np208/d44(aussie)/amc20(ARB)/BFG 35X12.5/Corbeau Moab Seats/RCI 6point Harness,Hella Aux lights/tuffy console/killer32 slider bars/custom bumpers and roll bar/Alpine head unit/amps/speakers 2002 Liberty Limited Early edition - Basically stock