The center bore is the diameter of the centre hole in the wheel which centers it over the mounting hub of the vehicle. It is normally referred to in millimetres.
PCD (Pitch Circle Diameter)
To measure a PCD on a wheel with an even number of stud holes, measure the distance from the centre of one stud to the center of the stud directly opposite. The PCD of a wheel, is the diameter of an imaginary circle drawn through the center of the stud holes, normally given in millimetres. To work out the PCD on a wheel with an odd number of stud holes, the chordal length is required. This is the distance from the center of one stud to the center of the stud hole adjacent to it.
The chordal length is then multiplied by the factor value against the matching number of studs given in the table opposite, which will equal the PCD. The majority of wheels have a standard PCD based on the number of studs and so as long as these measurements are fairly accurate, it should be easy to find the PCD. Again, if you are in any doubt then please do contact us.