Alloy terminology

Alloy terminology

Original Equipment
Refers to the parts on your car supplied by the original manufacturer.

The wheel width measured across the rim and inside the tyre flanges, and the wheel diameter measured from one tyre seat to the other.

Also referred to as the OFFSET or the E.T. This is the distance between the true centre line of the wheel and the hub mounting face.

P.C.D. Pitch Circle Diameter
This is the diameter of a circle scribed through the centres of the fixing holes.

The Wheel Fixings are either nuts or bolts of varying dimensions, ie diameter, thread pitch and seating. It is very important to use the correct nuts or bolts for the wheel.

The Bowl
The front central part of the wheel through which the wheel fixing nuts/bolts pass.

The back pad
The part of the wheel which comes into contact with the hub of the wheel.

A centrebore is the size of the hole at the back of the wheel which the hub fits into - clearly these need to match and fit property for the wheel to seat.

If you want to increase the wheel-diameter and reduce the tyre exposed, this is called up stepping.