I also think you are talking about Dayton Wheels, Have heard them referred to as California Wheels and East Coat Wheels. The center cast piece is the hub the wheel is just a ring held on by chocks and nuts. The rear duals have a spacer ring between them. When reinstalling them lightly tighten the nuts from one side of the wheel to the other a little at a time and give the wheel a spin checking to see that it is seating true it's like truing a spoked wheel.
They can be a pain but are supposed to be good for brake cooling.
