Dumb Wheel Question?

[firefighter184]

Might be a dumb question, but why does my wheel, stamped 15x8, actually measure 16 1/4? They all do. Edumacate me fellas.

 

[DEMON44]

Don't measure the bead lip. Only bead seat to bead seat, you'll find that more accurate.

 

[NoReGrEtS]

I beleave they measure them from bead seat to bead seat and not from the outer lip too outer lip