The Pitch Circle Diameter (PCD) is the diameter of the circle which passes through the centre of all the studs, wheel bolts or wheel rim holes.
The easiest way calculate the PCD is as follows:
Identify the size of rim or tyre size. (This helps to narrow down the likely PCD sizes)
Measure the distance 'S' between two adjacent studs from the centre of each hole.
Using the relevant formula below (depending on how many studs/holes you have) enter the measurement of 'S' and calculate the PCD
Depending on how accurately the measurement of 'S' has been the PCD should equal one included in the table below. This table should also be able to help identify the correct PCD if 'S' in a few milimeters out.
Note:
Imperial sizes are commonly used on UK trailers whereas European trailers use metric.
4 Studs/Holes
5 Studs/Holes
6 Studs/Holes
PCD Calculation Formula
4 Stud PCD =
S
0.7071
5 Stud PCD =
S
0.5878
6 Stud PCD =
S
0.5
Popular wheel Sizes & Stud Patterns
Rim Size
Studs
S
PCD
8"
3
76.90mm
88.8mm
8"
3
95.26mm
110mm
8"
4
70.71mm
100mm
8"
4
71.84mm
101.6mm (4")
8"
4
81.32mm
115mm
8"
4
91.92mm
130mm
10"
4
70.71mm
100mm
10"
4
71.84mm
101.6mm (4")
10"
4
79.20mm
112mm
10"
5
65.83mm
112mm
10"
4
81.32mm
115mm
10"
4
91.92mm
130mm
10"
4
98.78mm
139.7mm (5½")
12"
4
70.71mm
100mm
12"
4
71.84mm
101.6mm (4")
12"
5
65.83mm
112mm
12"
4
91.92mm
130mm
12"
4
98.78mm
139.7mm (5½")
12"
5
82.29mm
140mm
12"
5
97.04mm
165.1mm (6½")
13"
4
70.71mm
100mm
13"
4
79.20mm
112mm
13"
5
65.83mm
112mm
13"
4
91.92mm
130mm
13"
4
98.78mm
139.7mm (5½")
13"
5
82.29mm
140mm
13"
5
97.04mm
165.1mm (6½")
14"
4
70.71mm
100mm
14"
5
65.83mm
112mm
14"
5
82.29mm
140mm
14"
5
89.58mm
152.4mm (6")
14"
6
102.5mm
205mm
16"
5
97.04mm
165.1mm (6½")
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