What're Hub Centric Wheel Spacers Wheel Adapters?
The wheel spacers or wheel adapters are hub centric when they have two features, a) the spacers’ (or adapters’) center bore sizes are consistent with the outer diameters of the vehicle hubs; and, b) the spacers (or adapters) are made with wheel centric lips. The wheel centric lips’ outer diameters are consistent with the wheels’ center bore sizes. Please refer to below Pic #1 and Pic #2.
Based on these two features, the hub centric wheel spacers (or adapters) are able to, a) Center the wheels at the same manner before a spacer (or an adapter) is added; and, b) make sure the wheel studs, wheel bolts and wheel lug nuts seat in the center of the bolt holes at the same manner before a spacer (or an adapter) is added.
It’s very necessary to have the hub centric wheel spacers (or adapters), except that they could not fit in case of the limitation by the desirable thickness/width, or any other factors. Of course, on some occasions, it's unnecessary when the car hub height is tall enough still to center the wheel rims after the wheel spacers (or adapters) are added.
Originally, the vehicles’ wheels, wheel studs and wheel lug nuts, or wheel bolts all have fine sizes. However, the wheels are still be centered by the car hubs as normal. Apparently, this also tells the importance that the wheels shall be well centered.
When adding the wheel spacers or adapters, similarly, it’s important to have the wheel spacers or adapters firstly well centered by the car hubs, and then to have the wheels well centered by the wheel centric lips built on the wheel spacers or adapters. Namely, it’s important to have the hub centric wheel spacers or adapters in case there’s not specific limitation.
There are gaps between the wheel bolt holes and the wheel studs or bolts to make sure the wheel studs or bolts go through the holes smoothly. Theoretically, the conical or ball seat lug nuts, the conical or ball seat bolts could center the wheels well in case the lug nuts or bolts have fine sizes without issue of coaxiality. But in practice, it seems not enough yet. Otherwise, there shall not be necessary to have the car hub on the Wheel Trunk or Car Hub Ass’y.
For the non-hub centric wheel spacers or adapters, during the installation, it’s easily to happen that, a) the wheels are not exactly in the center, namely, not well centered; and, b) the wheel lug nuts are not seated well in the wheel holes; or the wheel bolt are not seated well in the wheel holes. For example, part of the conical seat does not touch the related wheel bolt hole. It also means the wheel studs or wheel bolts are not well in the center of the wheel bolt holes if the lug nuts or wheel bolts do not have concerntricity issues. In this case, it may easily cause vibration during driving. And the vibration will cause wheel studs or wheel bolts broken by the wheels or the wheel lug nuts.