In Willie's case he changed both the front wheel and sidecar wheel, so it could be that all his mph was improved from the decrease in frontal area of the sidecar wheel...and just as important it has less 'pumping' loss from the surface area of the tire dragging a layer of air along with it. Another big advantage of a fender is using it as a device to scrape off this layer of parasitic air mass(see pro stock drag racers here, been doing it awhile) . I think the siecar wheel for sure should be smaller and faired and have a air dam on the back to reduce pumping loss. The front as well should have the same, but not as important in the aero, but for sure in pumping loss. height of tire is more of an issue than width in my opinion, if you deal with pumping loss. All of the aero stuff isn't going to mater much if you use spokes...one step forward, two steps back kinda thing.
'WITH DISCS'...you think the disks could help direct airflow away from the inside of the wheel acting as a sort of 'disk' if you will? Most of the air is far outside that area at speed, but I haven't thought about that point that much, would lke to hear more opinoins on that one.
Hans
