My bro in law was just at this same crossroads.... he needed new tires and had "D" Ranier tires that were 2 years and 2 bubbles found .
He was going to get another set of "D" because "thats what came with" . . . .
After I he saw the weight ratings of the Raniers and compared them to the TT (Jayco 338 ) he was just under his MAX by less than 100lbs..( 25# per tire)
he now is the proud owner of the GY Endurance "E" and is leaving tonight for the first trip. Until he gets to a scale, he is going to air up to max as his wheels are rated for the pressure per the stamp on the inside.