Diameter is the nominal diameter on the tread at the base of the flange.
Rim shapes are approximate. Rectangular section rims vary from almost flat to slightly humped.
Tread is apparent and includes the tyre lip. See 'Use of terms' page.
Hub figures are outer diameter over the flat face and also distance out from the tyre.
Tyre width is from the front to the back of the wheel, not the thickness of the tread.