Properly fitted hub rings are actually really strong

 

indeed.^ when its all snugged up, its actually holding ALOT of weight.

Here OP, taken from wiki on wheel fitment:

CenterboreThe centerbore of a wheel is the size of the hole in the back of the wheel that centers it over the mounting hub of the car. Some factory wheels have a centerbore that matches exactly with the hub to reduce vibration by keeping the wheel centered. Wheels with the correct centerbore to the car they will be mounted on are known as hubcentric. Hubcentric wheels take the stress off the lug nuts, reducing the job of the lug nuts to center the wheel to the car. Wheels that are not hubcentric are known as lugcentric, as the job of centering is done by the lug nuts assuming they are properly torqued down.Centerbore on aftermarket wheels must be equal to or greater than that of the hub, otherwise the wheel cannot be mounted on the car. Many aftermarket wheels come with "hubcentric rings" that lock or slide into the back of the wheel to adapt a wheel with a larger centerbore to a smaller hub.[3] These adapters are usually made of plastic but also in aluminum.


http://en.wikipedia.org/wiki/Wheel_sizing

 

Hey bmc, that's really good information. My spacers do have those and I went ahead and retorqued all of them and used loctite. While it's not going to be fun getting them all off, I'd rather spend extra time pulling them off next time than having a wheel fall off.

 

All this is explained in the spacer thread, not sure why people keep having problems