Well, for the rear wheel rims it improved aero as it channels the hot expelled air flow from the brakes to the rear wing increasing its efficiency.
Obviously there are no wings to channel the air around immediately behind the front wheels, so what benefit can you get out of using them? Because we've already proven they don't help braking performance. Is there some other aerodynamic benefit from them?
Ben, great pics by the way
I agree the Ferrari are venting to the inside of the wheel on the rear by using the rim shields, but why is the front rim shield a more rounded profile than the rear one (which is perfectly flat)? And why does it stay in place instead of rotate with the wheel?
Well, I'm guessing it's for purely aerodynamic reasons. The ideal aerodynamic device on a rotating wheel would probably not rotate (causes a lot of drag), and you would want to make it a bit rounded as it would fill in some of the low pressure area on the side of the wheel. So, the optimal aerodynamic shape has been found, but it must really screw up brake cooling, so I would not expect to see these solutions on every race track unless they can do something about the cooling airflow. Possibly, they will vent to the inside of the wheel at some point, if not already. After all, they already have wings mounted to the inside of the hub.
I love to love Senna.