Went to rotate the tires on my 07 Prius today, and began by taking one of the beauty rings off. I had thought they were full covers, but found they are just plastic beauty rings. Can't imagine why they were put on there, other than increasing the aerodynamic properties of the spinning wheel. I can't imagine more than a 1% difference in wind resistance overall with those rings on, and after seeing how techno the rims look without them, I decided to leave them off. I'll store them away and maybe put them back on someday, but for now, they are off and staying off. Also on the way home today, I saw another red 07 Prius, and it was a Touring model. Sure see a lot of Prii around, but very few Touring models.
Hi DaveLeePrius, I think the rings are there to minimize rotational paddle-wheel drag. As the wheel rotates, the spokes act like paddle wheels in the air. By keeping the flow of air out of the outer diameter of the spokes, some air drag is reduced.
