where to find section width ?

[chimp koose]

I have been looking all over to find a section width for the bfg silvertown 285 70 15  . The literature states a section width of 11.5" but it states you can use a rim from 7.5 to 9.5 ". The section width will change with the rim size . Does anyone have a bfg silvertown 285 70 15 mounted on a rim that can give me a measured section width and the rim width they are using ? Please ? I am planning to use a 9" wide rim but I need to know the section width BEFORE I have the rims made . The T fenders are 11.5" wide and so is the stated section width of the tire . My plan is to run the tread out to just under the outside edge of the fender and have the sidewall out past the fender . 9" wide fender without the extension from the side of the body  w/8.6" tread centered side to side in the "fender ' part of the fender . I need to know the section width so I can get a reasonable amount of clearance to the inside of the wheel well . I can play with section width by using a different rim width . If the section width is 11.5" then I can have 1.5" clearance  at inner fender  

[Charlie Chops 1940]

I've never found anywhere that gives a number based on your specific rim width. I wouldn't expect much variance over the 2" rim width allowance for the tire size though.  It's more about front space and back space of your particular wheel and rear end width from wheel mount to wheel mount surface.