The pitch circle diameter is the distance between the center of a set of bolts and the new wheel. The pitch circle size of most cars is 4×100. This measurement should be taken in millimetres for the best results. For larger cars, some PCDs can be extended up to 130 millimetres in size. It is possible to also adapt to use five studs instead of 4. It is the distance between the centre point of a tire and the diameter of the studs. The manufacturer will provide the exact dimensions.
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How to Measure PCD?
It is actually quite simple to measure PCD. Measure between opposite studs to determine the measurement. This will usually give you a figure of 100mm. Although most PCDs will adhere to this rule, it’s worth measuring to get an exact figure. Deviations can lead to ill-fitting wheels that will require significant time and money to correct.
Some measurements are not always accurate, especially when you have to measure three or five studded parts. You can measure the diameter at the centre bore and the distance between the edge of the bore and the centre of any stud. Add the diameter to the distance between the centre studs and multiply this figure.
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Uses for PCD Measurements
To accurately fit new steel wheels or alloy replacements, a PCD measurement is required. Because of their light weight and elegant appearance, alloy wheels are highly recommended. It is crucial to fit alloy wheels to the correct PCD in order to make the right conversion. It is important to consider the offset measurements of the wheel and hub as well as the PCD measurement.
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The offset is the distance between the wheel of a vehicle and its body line. It should be sufficient to avoid any overlap with brakes calipers. While positive offsets are more common for front-facing mounts, negative offsets can be found on rear-facing mounts.
The two most important components in deciding whether to install new wheels are offset and PCD. Any measurement of the former should also be used with the latter for an informed decision.
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Installation and Safety
If you are familiar with changing tires or fitting alloy wheels, it is possible to measure the PCD. To properly remove and fit the tire and wheel, you will need to know how to lift a car. If you’re not properly trained, this process could prove dangerous. Ask your local garage for a measurement and fitting. The right PCD will allow you to organize your own fittings and replaces. It will also help you determine whether you can rely upon standard measurements or more specific figures when ordering new wheels.