COMPONENTS OF A LIGHT ALLOY WHEEL

Rim diameter:
The rim diameter corresponds to the interior diameter of the tyre in use and is quoted in inch.

Rim width:
The rim with (quoted in inch) indicates the inner distance between the two rim flanges.

Pitch circle diameter / pitch circle:
The pitch circle diameter indicates the diameter of the circle (in mm) of two opposite bolt holes. The pitch circle quotes the number of the holes. 

Offset:
The offset is the distance between the mounting surface and the rim’s centreline.

Hump:
The hump avoids a slipping of the tyre into the drop centre (e.g. when driving sharp bends)