Pitch Circle Diameter (PCD) is the diameter of the circle which passes
through the centre of all the studs, wheel bolts or wheel rim holes.
The easiest way calculate the PCD is as follows:
1) Identify the size of rim or tyre
size. (This helps to narrow down the likely PCD sizes)
2) Measure the distance 'S' between two adjacent studs from the centre of
3) Using the calculator enter the number of studs/holes and 'S' and
3) Using the relevant diagram depending on the number of studs
you have you should be
able to identify the correct PCD.
Imperial sizes are commonly used on UK trailers whereas European trailers use metric.