Originally Posted by Happy Prospector
You should stay with the same rating and tire size, that's what the factory installed. Besides what could possibly go wrong?
Lots of people upgrade tires, especially in consideration of what the "factory installed". Many factory wheel/tire combos are at 85%+ of rated capacity and that doesn't take into considerations such as not towing completely level (on a multi-axle) or forces involved in making a turn.
OP has it right. In order to consider going up a rating in terms of tires, he needs to consider the ratings of the wheels.