Scab
I agree, one must have downforce device(s) to keep the tires planted. For the downforce, the indy cars use wings [front and rear] and side pods with air movement to get ground effect. Racing today is getting and keeping traction. It is possible to have too much downforce/traction for the tires as we saw with Michelin based F1 cars at indy last year [michelin found the computer testing alone does not make for a good program].
Street motorcycles don't have these features. So the friction only makes lift. Salt flats bikes have shapes and wings to make downforce. 1950's GP bikes had aero shapes and made more speed per unit horsepower than todays GP bikes.
Ride safe.
rublenoon