I'm pretty sure all tires are measured unmounted at full pressure. The specs I've seen on customwheeloffset appear to be physically measured in that they vary from brand to brand and model to model. I believe they're doing more than the math on the label.
These nittos in 255 75 17 come in at 32.17
Nitto Trail Grappler LT255 75R17 (32.2x10.3R17) | 205-890 | Custom Offsets
Drive with confidence with these Nitto Trail Grappler Mud Terrain tires. This specific set of tires comes in a LT255/75R17 configuration with a Q speed indwww.customwheeloffset.com
The mickey thompsons come in at 31.97
Mickey Thompson Baja STZ 255 75R17 (31.9x7.8R17) | 90000001473 | Custom Offsets
Drive with confidence with these Mickey Thompson Baja STZ All Terrain tires. This specific set of tires comes in a 255/75R17 configuration with a T speed i
I'm curious to see what is listed for a tire you consider to be more accurately labeled. Perhaps some brands compensate a little to make up for real world usage.
My experience is with a dozen of so different size BFG tires over the past decade, but I personally haven't put a tape measure on a current production, mounted, inflated LT255/75R17 KO2 so there is a chance it measures true to the stated size. I have yet to see a single BFG measure remotely true to size in my life but anything is possible.
And for examples of other brands that I've recently measured...
Cooper measures pretty darn close, usually within 0.25" from what I've seen. Yokohama is spot on for the MTs I have on the GX now. Goodyears are pretty darn close. Interco is not even close, usually a good 1" less. Kanati is pretty darn good.
