What is a PCD measurement, and how do I calculate it?

“What is a wheel PCD? How do I calculate it?”, is a question we frequently hear from customers.

So, What is a Wheel PCD? The two main components for deciding on the installation of new wheels are:

  1. PCD is the diameter of the total number of studs
  2. and wheel or rim offset.

Due to the wide variety of rims and tyres a wheel offset calculator is not available.

The video below quickly identifies how to calculate wheel or rim offset.

wheel nut indicator

Click the image to purchase wheel indicators.

A number of factors decide the correct length of axle, they are

  • wheel width
  • wheel size
  • positive offset or negative offset
  • type of wheel and tyre
  • mounting surface
  • vehicle wheels and rim type

Technically, Pitch Circle Diameter (P.C.D.) is the diameter of the circle that passes through the centre of the wheel studs, wheel bolt holes, wheel rim holes or the bolt pattern.

This information is particularly useful for selecting the correct alloy wheel rim.

Vehicle manufacturers have difficulty providing a wheel offset size because car buyers often change the tyre size.

P.C.D. or wheel stud pattern is needed when you wish to replace a worn axle, hub, drums or disc rotors.

It is impossible to provide the correct hub or electric drum without knowing the exact wheel stud pattern.

Couplemate recommends installing wheel nut indicators to help prevents loosening wheel nuts.

Wheel PCD Measurement Calculation Formula

  • 4 Stud PCD = Stud distance divided by 0.7071 to get PCD
  • 5 Stud PCD = Stud distance divided by 0.5878 to get PCD
  • 6 Stud PCD = Stud distance divided by 0.5 to get PCD

Example, 67.185mm / 0.5878 for a five stud with 1/2″ studs is 114.3mm, which is a Ford Stud Pattern.

Finally, download a list of PCD’s from Al-ko by clicking this link.

News article on wheel nut indicators.