The professional name of the hub hole spacing is pitch circle diameter, which refers to the diameter between the fixed bolts in the center of the hub. Generally, most of the hub holes are 5 bolts and 4 bolts, but the bolt distances are also different, so we often hear 4X 103, 5X 1 14.3, 5x1/kloc. Take 5X 1 14.3 as an example, which means that the PCD of this hub is 1 14.3mm, and there are 5 bolts in the hole position.
It is often said that the width of the wheel hub is 7J and 8J, where the number represents the width of the wheel hub, while J only represents the shape and height of the wheel hub flange. Besides J, we also have C, JJ, JK, K, etc., which are mainly due to the difference of the protrusion height, with C being the lowest and K being the highest, and J being the most common wheel hub type. For example, 7J means that the distance between the flanges on both sides of the hub is 7 inches.