Here's the tires that we use on our 2005 E450 small Class C. Their maximum DRW vehicle weight carrying capacity - with the 4 in the rear inflated to 80lbs. each and the 2 in the front also inflated to 80 lbs. each - is 15,240 lbs. ... so they can handle the largest E450 based Class C IF IT'S WEIGHT IS DISTRIBUTED so as to not load the DRW rear 4 tires to more than 9,880 lbs. out of that total of 15,240 lbs..
Here's a source for the tires:
https://www.amazon.com/Michelin-Defender-All-Season-Radial-Tire/dp/B0192KRX7G/ref=pd_lpo_sbs_293_t_2...Look at this excellent data book on page 34 near the top to see the ratings for the 215/85R16/E size. Do the pressure versus load versus single/dual math to see where 9,880 lbs. and 15,240 lbs. come from:
https://www.michelinb2b.com/wps/b2bcontent/PDF/Truck_Tire_Data_Book.pdfI use the 215/85R16 Load Range E size - instead of the common E450 stock 225/75R16 Load Range E size - because I wanted a taller tire on our Class C so as to get a little more ground clearance. We do take our Class C off-highway on gravel and rocky roads, so a little bit of extra clearance helps. I use ~80 lbs. of pressure in the rear and ~65 lbs. of pressure in the front. The 80 lbs. of rear pressure is to keep heat due to sidewall flexing from being too great and so I can load up our Class C with no concern for tire over-loading. The 65 lbs. of front pressure is for the same reasons .... however, if I go to 80 lbs. in the front the steering becomes to "light and squirrelly" ... so I drop the front 2 tires down a bit from 80 lbs. to 65 lbs. to get a more solid steering feel.
The rear used to ride a bit harsh using 80 lbs. back there, but that was reduced through use of automatic variable damping shocks in the rear. For a larger Class C than ours, these kind of shocks in the rear may not be needed because of the higher average coach weight back there providing an overall softer ride at whatever tire pressures are being used back there.
2005 E450 Itasca 24V Class C