[aerohead]

*originally,you were going to mount the cover to the wheel.That infers a growth in frontal area.
*Adding the cover as an inner fender,mounted to the steering,with a smaller wheel/tire is something altogether different.
*You still have not reduced the wheelhouse volume.
*You're only going to reduce the clearance between the tire tread and inner face of inner fender.
*You still have the void between the outside of the inner fender and the interior face of the wheelhouse.
*You'll still have windage within the cavity of the inner fender.
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*If you can pull this off it's a good thing.
*The 1984 Probe-IV,with inner fenders and elastic urethane skirts was reported to enjoy a 9% drag reduction just with these front wheel modifications.
*There is no data for the a drag reduction for the inner fenders themselves.
*Full wheel skirt performance has been reported as low as 2% for total drag reduction.
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*The addition of wheels to a low drag car can double the drag,as in the case of the CNR car of 1978.
*Wheels on the 'Template' raise the drag from Cd 0.08,to 0.13.
*The 'cleaner you make your car,the more important will be the effect of the wheels/tires.