Technical Term
Center Bore (CB)
The size of the machined hole in the center of the wheel that fits onto the vehicle hub.
Deep Dive
The Center Bore ensures the wheel is perfectly centered. If the wheel bore is larger than the car hub (e.g., Wheel 72.6mm vs Car 66.6mm), you need "Spigot Rings" to fill the gap. If the wheel bore is smaller, it simply won't fit.
Related Concepts
Spigot RingsHub CentricVibration