If a person was to move up to a 16" rim, would the backspacing be a little less critical? (fj-40) I haven't done alot of searching, but it seems that what I've found so far, the 3-1/2" backspacing needed for a 15" is kind of a specialty.
I run 16" rims with 4" backspacing on mine. But my FJ40 still has drums up front, so this information is probably useless to almost everyone. They look like they will clear the calipers on a disc cruiser. I've got a disc brake axle in the garage, one of these days I'll find out for sure.