That's nuts, the rim fitting chart must be wrong.
All other 255/85's use a 6.5" to 7.5" rim, (BFG, Cooper and OS there's Dunlop, Toyo, etc who all make 255/85's and recommend the same rim sizes)
There is no way on God's green earth you'd get a 255 out on the bead of a 9" rim, some 265/75's are hard enough to mount on an 8" rim.
[edit] I just checked the US Maxxis site and the fitting rim width is 7"
MT-762 Bighorn which usually means you can go 1/2" either way in width on 4WD tyres.
The Oz importer (IIRC it's Tyremax) have published the wrong (and potentially dangerous) data if they call for 7.5" to 9.0" rims