PCD (Pitch Circle Diameter) is the measurement of the diameter of the imaginary circle drawn through all of the wheel bolts or studs on a wheel. It is also known as the 'bolt circle'.
A wheel's PCD is usually displayed after the number of studs, separated by a slash. Hence a 'pcd' of 5/120 means that the wheel has five studs, and a pitch circle diameter of 120mm. A 'pcd' of 4/114.3 means the wheel is four stud with a pitch circle diameter of 114.3mm.
Measuring the PCD of a 5 stud wheel is a tricky business. It is much easier to determine the PCD by checking the manufacturers' original specifications or by checking our PCD reference guide for each model, (see our homepage). It is possible to roughly measure the PCD of a 4 stud wheel, as the pitch circle diameter is the same as the distance between two opposite bolt centres.
Different cars have different PCDs, but often similar cars within the same manufacturers group have the same PCD. Many of the VW Golf-sized cars in the VAG range have the same PCD and other wheel dimensions, meaning that wheels are often interchangeable between these cars.
For more information on PCD, see 'bolt circle' on Wikipedia: