http://www.contour.org/ubbthreads/showflat.php?Cat=&Board=wheels&Number=875255First off, let me apologize for my attitude in that thread. I was a relative noob who had a lot to learn about how to discuss something online.
I've done a lot of research since then, and I've determined that we were both right. Basically, a lugcentric setup with no rings should work fine. The tapers do a good enough job of centering the wheels that carefuly mounting will result in a balanced setup. The friction between the hub face and wheel carries the load, as we all agreed in that thread.
BUT, rings do not only help make the mounting easier, they actually bear some force. I've seen a lot of pictures of fretting on rotor hats from play in the system - properly torqued ones, at that. You do end up asking the studs to take shear loads, which is a very bad thing.
Now, Miata guys will fight this all day. A Miata uses the same stud size and number as the Contour, weighs 1000lbs less, and is rwd with 50/50 weight distribution. The front wheels on a Contour have 1000lbs each on them, and do all the driving and essentially all of the braking. This means you have fully reversing forces in two dimensions on each stud, which is horrible for fatigue! The Miata has 500 lbs on each wheel, and the driven rears do very little braking. With 4 M12 studs, just like us.
Of course, you can get lucky. Things for mass consumption are overbuilt, and even racing without rings won't break anything. But I ran without and had stud breakage. Weargle had stud breakage, I believe without rings (Wes, details?). 4 small studs are not much for a fat car like this, so get good tight rings and give them every chance you can!
