Do we have any A-B-A testing on a mod like this? I'm skeptical, although the surface area is smaller, the form of your replacement mirror is less aero than stock.
For example, look at these shapes:
(Source: Wikipedia on
Drag Coefficient.)
I'm thinking half-sphere .42, vs short-cylinder 1.15. If the Cd difference were that large (it may not be), you'd have to cut the mirror area by almost 3X just to break even.
The effectiveness of this mod might be 0.
EDIT: Sorry, I was probably being a bit pessimistic. I have a bicycle mirror like that and I remember it being a bit curved on the back side. Also I reread and found where redneck said:
Quote:
New mirror is approximately 3sq.inches.
Old mirror is 10-15x that total. (size of mirror and mounting)
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If so then even a 3X increase in Cd would translate to 3-5X decrease in CdA.
But I think my underlying point is valid; be careful selecting a smaller mirror, and A-B-A testing would be interesting.