TRAILER TYRES & WHEELS

CHOOSING THE CORRECT WHEELS

Under wheel description the term p.c.d is used which stands for pitch circle diameter. The number of bolts used to install a wheel varies from 3 to 8 studs depending on the vehicle make and model. The pitch is the diameter (mm) of the circle that intersects the stud centres. To fix a wheel correctly, the number of studs and the pitch should be the same on the vehicle and the wheel.

On a 4 stud wheel it is simply a case of measuring from centre to centre on opposite studs. The following formulas can be used on 3, 5 and 6 stud wheels to work out PCD.

3-stud - Length 'X' x 1.154
5-stud - Length 'X' x 1.7012
6-stud - Length 'X' x 2

Finally PCD can be measured in metric or imperial so a "4 stud 4N p.c.d wheel" has a pcd of 4 inches with N standing for a cutout in the rim used to access a grease nipple. A "4 stud 100mm p.c.d wheel" is the modern metric equivalent.