My $. 02 on tires is this:
Don't buy the cheapest things you can buy. Many tire dealers can choose from rubber grades, steel belting grades, etc. The stuff that doesn't make "A" grade for the name brand guys (Michelin, Kelly, Bridgestone, Etc. ) goes to the "private" brand guy. Namely these are tires (and I won't name them) made by national companies but with cheaper quality materials.
Consider a 7. 50R16 radial tire as an option to the 235/85R16. They have the same height, a similar load capacity, and dual spacing is much better. My first CTD was a 93 Club Cab Dually. After the factory Goodyears wore out, I switched to 7. 50R16 Bridgestone VSX's. They had a 10 ply or even a 14 (!) ply option. I elected to use 10 ply's and they still looked great after 60K when I sold the truck. The only drawback to this size is that they will be harder to find. But if you carry a heavy load and dual spacing worries you (it should), consider this as an option.