Wow, those would be huge! Just kidding, I'm sure you meant 255 x 60 x 18
Tire pressure is just something you should mess around a little with yourself. The more pressure, the better the gas mileage and the harsher the ride. People generally put a little more in the rear than the front b/c that's what LR calls for. Personally, I go about 40 rear and 38 front. Dropping down a few lbs. makes the ride quite a bit softer. It just depends on your preference really.