Hubcentric rings as the name implies, centers the wheel onto the hub. Lug nuts alone cannot do this sufficiently enough to remove the out of alignment inherent when you try to line up a big hole over a slightly smaller shaft (i.e. the wheel hub bore over the hub mounting ring).
Once the rings align the wheel centrally to the hub the FRICTION between the wheel face and the hub face is what actually carries the weight of the vehicle, NOT the rings and NOT the studs either.
The point of ths post is that without the rings you will NEVER be able to align the wheel to the hub properly and you will get virbration, not matter how perfect the wheel and tire balancing may be.
End of story.
