Wheel Cross Section

The below diagram may help in the understanding of basic wheel terminology.  Some of the basic definitions are stated below the diagram.

Backspacing -- The distance from the mounting pad/surface of the wheel to the farthest point of the backside of the rim, usually measured in inches.

Centerline -- The center point of the wheel from the face to the backside of the wheel.

Offset -- The distance between the centerline of the wheel and the mounting pad, usually measured in millimeters.  Positive offset wheels have the pad more to the face of the wheel.

Wheel Diameter -- The width of the wheel from the front bead seat to the rear bead seat.  This is not the overall wheel width.