the clamping force is what holds the wheel in place, the centering ring is there to help center the wheel when you install it for balancing purposes
if you're shearing the bolts/studs, that means you've surpassed the clamping force.
in my own experience, most people do not install their wheels correctly, even racers
without rings, the procedure is to hand tighten in a start pattern, SLOWLY (the most important part that is often ignored, esp by users of air/power tools), so that the centering force of each individual nut brings the entire wheel into proper alignment. Final torquing should be done with the wheel in the air.
hell, this should be the procedure even WITH the rings, as this will guarantee the most balanced installation
sources:
http://www.tirerack.com/FAQ/results.jsp?category=Wheels (read the lug and hub centric bits)
http://www.prestigewheel.com/Catalog/HubRings66_67.pdf
i have personally corrected many "vibrating wheels" after leaving various mechanics by simply re-installing the wheels by hand and standard torque wrench.
edit, more reading material
http://www.metalconsult.com/articles...20Failures.pdf