Depends on how much you want to spend to keep the required dual spacing and clearance. I have seen 315/75-16 tires on a dually, but he spent 500 dollars for the spacers to do it and also had a 6" lift on it. It was a 2003 F350 4x4 PSD dually.
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86 F250 HD 6.9 IDI ATS turbo "not exactly" stock 4x4 T19 BW1345 3.55LS both ends D60 front, 10.25" Sterling rear, ram air, dual stacks.
I run LT265-75-R16E Firestones on my dually. These are 1.18" wider than the stock LT235-85-R16Es. There is a gap about 1 inch wide all around the tires, EXCEPT down at the bottom, where the tires are spread out. Down there, the gap is only about 1/2" - 5/8". Your best traction will be with the narrowest tire you can run, but wider tires look better, I know. 275 series tires would be about .4" wider, so they might actually fit onto the truck, but they would come mighty close to touching. 285s would definitely touch each other. To fill up the wheel-well, a taller tire would work. My 265s are virtually the same height as the stock size since they are 75s instead of 85s. To figure out what size tires you want, just do the math yourself:
The 75 or 85 means that the sidewall heights are 75% or 85% of the width, so
10.433 inches x .75 = 7.825 inches
or
9.252 inches x .85 = 7.864 inches
To calculate the tire height, just double the sidewall height and add the rim size:
2(7.825) + 16 =
15.65 + 16 = 31.65 inches
or
2(7.864) + 16 =
15.728 + 16 = 31.728 inches
(see that both of these tires are about the same height?)
Get a number in mind, do the calculations, and then search to see if your favorite tire maker makes the size you want. If not, then you can see what their closest offering is. Remember that a tire that is 1 inch taller will only fill up an additional 1/2 inch because the tire will be 1/2 inch bigger at the top, and 1/2 inch bigger at the bottom. Also, if traction in snow is important at any time, then you might want to think about going as narrow as you can stand.........
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