They are 17's, but I have back to back experience with 285/70R17 to 255/80R17 to 265/70R17 LRE tires on 17x8" rims with similar weights.
The 285 and the 265's felt the same, even thou the 285 has a taller sidewall the load capacity was 555 lb/tire more on the 285's so I presume that is part of the reason they felt the same.
The 255 took more air on the front tires to have the same stability as the 285 or 265's did while towing (even thou my FAW is lower towing than empty the physics in a corner are different). Both the 255 and 265 where rated the same, at 3195/tire.
I now run 245/70R19.5 and between the LRG and stiffer/thicker sidewalls the comparison is like a P to a LRE LT.
Toyo moved their M-55 to the Light Commercial tab, but it doesn't appear to be loading.
http://toyotires.com/tire/pattern/m-55-on-off-road-commercial-traction-tires
I have heard nothing but good things about the Goodyear Duratrac's.