How heavy is your Jeep?
I had 33x12.50-15s on my JK for a while and ran them at 25 PSI for the best contact patch. You need to see how heavy your Jeep is, then see what the total of the load capacity of your tires is. Then you'll know what percentage of their capacity you are using and you can set your PSI accordingly. Most guys will need 20-30 psi for the road depending on configuration of your vehicle.
'92 YJ - heavily modded
'96 ZJ - heavily modded
'05 KJ CRD Limited - 370 lb./ft. from a 4-cylinder and trail ready. Pure awesomeness.
'11 Mango Tango JKU Sport - Mods
'12 Dozer JKU Sport S - 6-speed - ACE rock rails - Max Tow package - Daystar spacers - 33x12.50 Duratracs