Aero suspension
 

I was wondering. If you make a (full or partial) airdam, you increase fontal surface. But what abouth makin a dam just for the weels, and schape the suspension whit plastics for minimum resistance. Would that work, and has it been done? Because you can then make a full belly pan with standard frontal surface and stil direct the flow around de suspension, the disturbt flow in corners would be nothing because we will be going strait most of the time.

Check the Toyota Prius and Basjoos's Aero Civic as well as many others. We sometimes refer to them as wheel strakes.

suspension
 

The belly pan should enclose most of the suspension,just allowing for wheel flop of the turning wheels,and deflection of the rears.
Any voids which are associated with the turning wheels are treated with spats which prevent straight-line shear flow
into these areas ( like tires on the roof a mobile home in West Texas ).
Low drag cars will have canoe-fairings for and aft of the tires to minimize pressure spikes and turbulence associated with the revolving rubber.
When 'out of town' they may 'drop' the car with active suspension also,which reduces frontal area , increases the fineness ratio,and configures the inclination of the car for lowest drag. Ford's Probe-IV concept car of 1984 would be an example.