...Did some more searching...:scratch:
..Here is a recent thread with info on the hubcentric rings in post #21..
http://www.explorerforum.com/forums/showthread.php?p=2071791
...This is from here..
http://www.wheelfire.com/ccontent/TechWheel.cfm#Centerbore
Centerbore and Hubcentric Rings
This refers to the center bore in the wheel that centers the wheel on the hub of the car. Since most wheels are mass produced, they have a large center bore to accommodate several different vehicles. If there is a vibration problem, it is recommended that you use hub centric rings. Hub rings are hard plastic rings that link the wheel to the vehicle. This centers the wheel and makes your wheel hub centric. Without hub rings it is possible to get vibrations even if the wheel and tire package is completely balanced.
...And someone else sent me this..:biggthump
.."Ford put hub-centric wheels on your 4x4 truck, that's what you should replace them with. The hubs and lugs on the truck were not designed to handle the added strain of lug-centric wheels.
Hub-Centricity
When automobile manufacturers design a vehicle, they utilize hub-centric wheels so that:
* The wheels are positioned very precisely on the car.
* The possibility of shifting while being mounted is minimized.
Hub centric wheels mount on an off-the-car wheel balancer by a precision ground and hardened cone that is forced into the center hole. This works quites well, and is very important. The idea is that the whole wheel/tire assembly should rotate on the balancer exactly about the same axis that it rotates on the vehicle. If it doesn't, then it can be "in balance" on the balancer but "out of balance" on the vehicle. As an example, a 60 lb. wheel/tire assembly that is mislocated on the balancer shaft by 0.005" and then balanced there will be out of balance by 0.6 ounces when it is mounted on the vehicle.
Lug-Centricity
The alternative to a hub-centric wheel is known as lug-centric.
* The wheels are located solely by the lug nuts rather than the wheel hub.
* As the lug nuts are tightened, they adjust the wheel's position relative to the hub, thus centering the wheel.
* Properly torqued, the lug nuts continue to keep the wheel centered as the vehicle is driven.
*Lug-centric rims are more prone to splitting and cracking aroung the stud holes.
Lug-centric wheels require extra care in mounting on a vehicle. A wheel that is lug centric often doesn't have a precisely machined or punched center hole, and so mounting it to the balancer using a centering cone can result in very poor balance. In such cases, a lug based adapter (commonly known as a "Haweka" adapter because Haweka makes a good one) is used. The adapter mounts on the balancer and has adjustable lugs that mate to the wheel, and the wheel is then mounted to the adapter. When used properly, it works well, and it should always be used with lug centric wheels.
When using shouldered nuts instead of tapered nuts, take extra care to properly locate the wheel. Never use air tools to install high performance wheels! Always use a torque wrench and follow accepted tightening procedures. "
