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Technical Information

This information & diagrams are to help you understand Offsets, PCDs (Pitch Circle Diameter), Centre Bores and Caliper Clearance.

Skip to a section: Offsets PCDs Centre Bores Caliper Clearance


To work out the offset the wheel must be measured accurately using the following steps and using Diagram 1 & Diagram 2

  1. Measure the overall width of the wheel - OW *
  2. Measure the ‘T’ dimension, which is the measurement from the back of the bolt up face to the outside of the inner rim
  3. Divide the overall width by two which gives you the centre line.
  4. Minus the centre line from the ‘T’ dimension.
ET = T -  OW

* Please ensure wheel has equal size kerb edges.


“The Pitch Circle Diameter is the diameter of the circumference of the centre line of the drilling holes.” see Diagram 3

This can be four, five or six lug and can be measured as shown in Diagram B. The easiest way of measuring four or six lug wheels is to take two diagonal holes and measure from the outer edge of one hole to the inner edge of the second hole.
With five lug wheels this is not possible as there is not two diagonal holes, therefore the simplified way would be to measure the outer circumference and inner circumference of the drilling holes. The difference should be divided by two added onto the smaller circumference or deduced from the larger circumference.

Compomotive do manufacture 8 hole multifitment wheels therefore it is essential when fitting these wheels that the correct PCD is selected.

Centre Bore

“The centre bore is the location hole machined in the centre of the wheel.”
This varies from one vehicle to another. It is essential, the wheels purchased have the correct centre bore for the vehicle they are to suit, otherwise you may experience balancing problems. Compomotive do manufacture wheels which are universal fitting and are drilled to fit a variety of vehicles. Therefore to obtain the correct fit for the vehicle the correct spigot rings must be inserted into the rear of the wheel.

Caliper Clearance

Some vehicles as standard are produced using large brake calipers, therefore our listings have taken this into account when advising fitments.
However a customer may have modified the brakes on their vehicle, if so it is essential you advise us of this.
Should you have any trouble understanding this, please do not hesitate to contact us for expert help.

Please see Diagram 1 & Diagram 2 & Brake spec sheet and advise us of the following:

 A = Caliper protusion from hub face
 B = Proximity of caliper to hub centerline
 C = Depth of caliper
 D = Radial depth of chamfer
 E = Lateral depth of chamfer

Wheel Dynamics
 OW = Overall width of wheel
 T = Backspace of wheel
 ET = Offset (Einpresstiefe)