This is the second time this season that I hear from people that had issues with forgetting to pull hub rings off the hub while swapping wheels. In both cases leading to NVH which could have been avoided by just leaving the plastic rings in their packaging. Hub rings CAN help mount the wheel for beginners, or those who aren't strong enough to hold it up while the nuts are being threaded. They are also very useful when mounting wheels on vehicles (VW, Audi, BMW, Merc) that use lug bolts; these vehicles have flat rotors, and therefore they can't just hang the wheel on the studs while preparing to thread the lug nuts.
Slightly off topic read:
Our wheels are lug-centric. The conical shape of the lug nut means that the lugs are used to center the wheel. It's far more precise and efficient that hub centric rings. If you are all very curious, I can attempt to present the math which will prove to you that once the wheels are mounted and torqued, the friction between the face of the hub and backside of the wheel is what transfers the road force, and it has nothing to do with aluminium or plastic hub rings. I'd present the math from an engineering perspective, since that is my background as a structural engineer that regularly designs bolted connections.
As a quick thought experiments consider this: Hub centric rings have an imperfect fit otherwise it would be next to impossible to get the wheel over the axle flanges, especially when corrosion develops around the mating surfaces of the rings. Wheels rotate at highway speed at hundreds of RPM (around 700RPM at highway for many cars). This would induce friction wearing on the face of the hub, and when we pulled the wheels off a car after a season, we'd see shiny spots where the wheels were making contact with the hub, rather than corrosion, as you can see in the image above. We can conclusively say that wheels are attached to a vehicle by the clamping force the lugs provide from wheel to hub (shear friction), and not by bearing against the hub (or lugs, although I didn't prove it's not bearing in the lugs).
