Trailer and caravan wheels how to find the PCD.

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With our large range of trailer wheels and tyres we are finding that we are regually asked what PCD means so we aim to make it very easy to work this out after reading this guide.

First of all What does PCD mean?

PCD stands for Pitch Centre Diameter. It is the diameter of a circle that is used to set the wheel nuts on.

As shown on the diagram above it is easy to find the PCD on a 4 stud wheel. Just measure from the centre of one stud to the centre the opposite stud. This will work for any even number of studs.

Please note there are two PCDs that are very similar. These are 4" (101.6mm) and 100mm; as these are so close some people get some measurements wrong as they just read as 4" if they are used to using imperial measurements or read 100mm if they are used to metric measurements. Later in this guide there some diagrams showing all the most popular PCDs used and stud sizes used. These will also help you measure.

For other stud patterns ie 3 or 5 stud the above way will not work. There is another way that will work on any stud pattern including those with an even amount of studs. The two measurements shown on the diagram below labelled as A and B are needed:

Dimension A is the diameter of the centre bore (hole in the middle of the wheel)

Dimension B is the distance from the edge of the centre bore to the centre of any stud.

To work out the PCD is easy. Simply add A + B + B. See example below:

To work the PCD shown above it is just 66 + 23 + 23 = 112mm

Below are a few of the most popular PCD's used on Trailer wheels and the types of trailer that they are used on.

This is probably the most common PCD used on small trailers. It has a 3/8" stud. Due to the size of the studs it is limited to wheel size and weight capacity. This is not advised to be used on wheels larger than 10" and weights above 750kg per axle. This is also the PCD used on old mini wheels. There was a heavy duty 4" PCD used in the past this gave extra carrying capacity and allowed larger wheels to be used. It had a 7/16" (11.1mm) stud and was used on Indespension wheels and also old Towavan amongst others. This has been superseeded by 4 stud on 100mm PCD shown below.

4 x 100mm can be used on smaller trailers that require larger wheels. The carrying capacity is higher as the studs are larger (12mm) and this gives a stronger fixing point. This PCD is often used on caravans as there is not a large weight on them.

4 x 5.5" is a commonly used PCD it comes with either a 12mm or 1/2" (12.7mm) stud. This is a heavy duty 4 stud pattern. We do not recommend using on weights much above 1300kg per axle. We tend to use this on all braked suspension up to 1300kg per axle. Also a lot of other trailer manufactures use this on their units.

4 x 115mm is used on European trailers but in the UK it seems to be used on small flat pack trailers such as Erde, Daxara and our smaller General Purpose Trailer (maypole MP711)

5 Stud PCD's

5 x 6.5" (165.1mm) is a very popular PCD as it will accommodate any trailer weight and more with a large diameter stud either 16mm or 5/8inch (15.875mm). It is used by Ifor williams and many other trailer manufacturers. We try and use it on all wheels and suspension 1500kg and above.

5 x 112mm is used on small wheels for building low trailers ie 195 x 55 x 10. These are used by Brian James and Bateson trailers, mainly for the large flat bed or beavertail car transporters when the bed needs to be low. The small wheel and tyre listed above is used on low tri axle trailers. It has a 12mm stud and we would not recommend using on axle weights over 1500kg.

5 x 140mm PCD is another common size and it is a good weight carrying pattern, but there is no reason I would choose to use this for making a trailer. However, we do stock a few wheels and tyre on this PCD to sell as replacements. We can also get suspension units and axles on this PCD. This is used on some Indespension trailers.

Please look at some of our other guides on ebay by using the links below

Trailer plug guide and wiring diagrams

Requirements for trailer lighting

EC94/20 and what it means for towbars

Different types of towbars and their different uses

Towbar wiring ( relays and dedicated wiring systems)

For our related trailer / caravan parts please use the links below

Wheels and Tyres

Trailer suspension and replacement parts

or you could view our Ebay Shop for the largest range of trailer and towing parts and accesories on ebay

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