There's more information about this at this thread: http://www.airforums.com/forums/f438...ari-51030.html
I've called Michelin, Dexter Axle and Airstream to get more information and posted it on that thread.
Clearance for 16" wheels and tires is different for different Airstreams, so if you are thinking of changing, check tire sites for diameter of tires compared to OEM tires, measure space to cut out and between tires, do it several more times, and then measure again. You wouldn't want to spend $1,000 or more on Michelin LTX or RBS tires and new wheels and not have them fit. And, don't forget you'll need 5 wheels and tires.