I'm going to pick up my second hand hummer rims this weekend and have been looking at tires for them......well......every 315/70/17 I've found is rated the same weight wise, no matter if it's D or E rated (all at 3195#'s)......that said my current set up has 285/75/16's and they are rated at 3750#'s.....while I don't tow heavy all the time, I sometimes do some fairly heavy hauling......will there be that big a difference in the 17's vs 16's? thanks for your suggestions Chris....... a couple of pics:
http://i7.photobucket.com/albums/y291/moloss/truck%20pics/IMG_5072.jpg
http://i7.photobucket.com/albums/y291/moloss/hayontruckmay2009.jpg

Yup, but you can air the E's up to 80psi and the D's to only 60 or 65psi. Higher psi will keep the tire more firm.

On edit: I'm not sure why the 315's are rated at 3195, I can only think that since the H2's are the primary users, they cater to the axle weight rating and wheel weight ratings for that truck. A lot of the times the auto people will ask the tire people to make a size that is uniform with all those ratings (axle, wheel GCVWR etc....). My buddy with an 09 F350 has the 275/70 18 and his are like at 3800lbs. Go figure, ford has specific weight ratings for payload and want the tire to match. Just my thoughts and from talking with a few people here and there about that same thing a while back. Hope it helps.

LA DMAX