Originally Posted by zabeard
Ah idk you will have to explain that to me later.
if they were directly related one would always increase/decrease in relation to the other.
now, take a look at your diagram. keep the BS the same, but make the wheel wider. when you make the wheel wider, you also hafta move the centerline. movin the centerline w/o adjustin the mounting location(fixed BS) changes the wheel offset.
they are measured from different points in such a way that they cannot always be directly related. especially when you figure that BS is measured from the backside lip and the centerline is an imaginary point between the tire mountin surfaces, completely disregarding the lip of the rim.