How to measure wheel width?

[joshw02]

How do you measure the exact wheel width? Outside to outside of the lip or inside to inside?

[Teaguer]

Inside to inside .

Although it is never exactly what you think it should be .

[GaryE30]

They have tools that clamp to the outside to tell width at one of the BMW garage's I worked at this past summer.

[SchnellerVert]

Inside flange to inside flange.