I have an 03 2500 4x4 running 20's. The reason I went to 20's is that I carry a heavy cab over camper much of the year, and even with load helper springs, I got too much sway with the load. This I went to a shorter sidewall tire and that made all the difference in the world.
Yet I have run two sets of tires in 35000 miles and it is killing me. The tires I have used are the Toyo's, good and grabby but good for only 20,000 miles max. I have not been able to find any options other than these that would garner me more mileage or less cost. Any suggestions would be greatly appreciated.

As a side note, when I put the tires on I had no reduction in mileage: 22 hwy, 17 city

 

Sorry to say, but you should have probably gone to 19.5's or 22.5's as i've heard those tires last for 200k miles or something crazy like that...

 

Try Goodyear Wrangler AT/S in LT275/65-20. More of a street tire that should have better longevity.

 

itch, Do you have 20X 8,9 or 10s? Don't try nittos, there worse than the Toyos on mine. I've had two sets of 305/55/20s now, and I think I'll try 325/60/20s if they will fit, does anyone know for sure??? Those 275/65/20s are almost 35" and pretty skinny.

 

I have the 20X9 wheels, they are a good tire but longevity is awful at $331 a piece.

 

you could think about some mickey thompson baja claws i had a set on my 03 1500 for 43k before i traded it in on my truck now and a friend of mine got close to 50k with his f250 ps on 35's

 

I have the Nitto Terra Grapplers, 275/65R20 on 20X8.5's. They are a 10 ply tire with a load rating of 3750 @ 80 PSI. The specs are 34 inches tall, 11 inches wide. Fit fine without leveling. The key to making them last is rotate religiously(so I hear) Mine have been on for about 1500 miles. So far , so good.