Steering Wheel Bolt Patterns
Overview
There’s a fair bit of confusion regarding steering wheel bolt patterns and how to measure them. Generally, there are three things you need to know:
The number of bolts being used.
The thread size of the bolts holding the wheel.
The diameter of the circle that passes through the center of all of the bolt holes, also known as the Pitch Circle Diameter (PCD).
There are other ways to measure the bolt pattern, including distance between bolts (DBB), bolt circle radius, and pattern angle.
A problem comes up when you have an odd number of bolts. This means you have an asymmetric pattern, and can’t measure the diameter easily. You can estimate the bolt circle on a 5 bolt wheel by measuring from the center of one bolt to the far edge of the furthest bolt away.
An exact calculation can be done as follows:
Measure the distance between two bolts (DBB)
Find the angle between bolts (ABB). For example, 360 degrees / 5 bolts = 72 degrees.
Calculate the bolt circle diameter by the formula BDC = DBB / sin (ABB/2)
Common Bolt Patterns
Below is a table of common bolt patterns used by various manufacturers.
Manufacturer | Bolt Count | Bolt Circle | Notes |
---|---|---|---|
Grant | 3 | 1.750 in / 44.45 mm | |
Grant | 5 | 2.871 in / 72.92 mm | 1.6875 in / 42.86 mm distance bolt to bolt |
Circuit Performance | 5 | 2.756 in / 70 mm | |
Nardi | 6 | 2.913 in / 74 mm | |
Grant | 6 | 2.750 in / 69.85 mm | Will usually fit 70 mm |
Circuit Performance | 6 | 2.756 in / 70 mm | Will usually fit 2.750 in |
Formuling | 9 | 4.000 in / 101.6 mm |