What is a P.C.D. measurement, and how do I calculate it?
“What is a wheel P.C.D.? How do I calculate it?” are two frequent questions we hear from our customers.
PCD stands for Pitch Circle Diameter. It is the diameter of a circle that passes through the centre of the lug holes on a wheel. The PCD is used to determine the compatibility of wheels with a particular vehicle or trailer.
For example, a caravan or trailer wheel with a PCD of 5×114.30 means that there are 5 lug holes spaced 114.30mm apart on a circle. This PCD is commonly used on caravans and trailers that are manufactured in Europe.
It is important to match the PCD of the wheels to the PCD of the hub on the trailer or caravan. If the PCDs do not match, the wheels will not fit properly and could potentially come loose while driving.
When installing two new wheels, the two main components needed are:
- Wheel P.C.D. (the diameter of the total number of studs)
- Wheel or rim offset.
This is due to the wide variety of rims and tyres available on the market.
Why is P.C.D. Important?
Several factors decide the correct length of the axle. These are:
- Wheel width,
- Wheel size,
- Positive offset or negative offset,
- Type of wheel and tyre,
- Mounting surface,
- Vehicle wheels and rim type
In technical terms, Pitch Circle Diameter (P.C.D.) is the circle diameter that passes through the centre of the wheel studs, wheel bolt holes, wheel rim holes or the bolt pattern. This information is handy 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, drum or disc rotor. It is impossible to provide the correct hub or electric drum without knowing the exact wheel stud pattern.
We recommend installing wheel nut indicators to help prevents loosening wheel nuts. Read our news article on wheel nut indicators here.
Wheel P.C.D. 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
For example, 67.185mm / 0.5878 for a five stud with 1/2″ studs is 114.3mm, a Ford Stud Pattern.
For further clarification, AL-KO has a list of all available P.C.D.s for further clarification. Click this link here.