Getting ready to put new tires on my fifth wheel. Definitely going to get LT tires with a high load capacity- Will send this unit down the road in a year or two so I don't want to buy 17.5 " wheels so...
However, as "He Who Shall Not Be Named" has posted, strictly speaking you are not supposed to replace tires with lower rated tires than what were originally on the unit. Just a heads up.