Are 325/50/15 DR's wider than 28x10 slicks on a 10" rim?

[SPOT MY 6]

BFG's website says that on a 10" rim, their 325/50/15's section width is 13.0"

Hoosier's website says that on an 8" rim, their 28x10 slick's section width is 11.7"


I think I remember reading somewhere that when you increase the rim width by 1", that the section width of the tire increases by .3".

So with this theory, the Hoosier tire on a 10" rim would have a section width of 12.3", right? This would mean the BFG is .7" wider than the slick on the same 10" rim?

 

[S10xGN]

I've got Hoosier QT 325-50x15's on 10" rims that measure 12.8"w x 27.8"h. Air pressure may figure in there somewhere too ...