Bolt Circle and Wheel Hub
The bolt circle is the diameter of an imaginary circle passing through the wheel center holes. Bolt circles have either 4, 5, 6 or 8 bolts. The measure (in millimeters or inches) is equal to the distance between the two farthest holes, or taken with an instrument that indicates the diameter of the circle between two closest holes.
How to measure the "Bolt-circle" (BC)
- Depending on the pattern, measure the distance in millimeters between the lines (as illustrated)
Here is a table of conversion of measurements in millimeters and inches:
|4 x 3.93||4 x 100|
|4 x 4.25||4 x 107.95|
|4 x 4.33||4 x 110|
|4 x 4.50||4 x 114.3|
|4 x 5.12||4 x 130|
|4 x 5.51||4 x 140|
|5 x 4.00||5 x 100|
|5 x 4.25||5 x 107.95|
|5 x 4.50||5 x 114.3|
|5 x 4.53||5 x 115|
|5 x 4.72||5 x 120|
|5 x 4.75||5 x 120.65|
|5 x 5.12||5 x 130|
The wheel hub is a machined opening (measured in millimeters)located behind the center of the wheel, allowing it to sit properly on the vehicle axle. This opening is designed so that the center of the wheel is perfectly centered with the vehicle when the bolts are tightened.
Some wheels are specifically made to be installed on specific vehicle models (see the replica wheels), while other wheels are designed with a larger opening to suit a greater number of cars.
How to measure a wheel
- Measure the distance in inches between where the tire is supported (#1)
- Measure the distance in inches between the rim's interior beads (#2)