Quote:
Originally Posted by christofoo
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:
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. |
I have this mirror on 3 of my bikes. The backside of the mirror is flat for about 5/8 of its area, then the corners are rounded with the radius approximately equal to 3/4 of the mirror thickness. Imagine the half-sphere with the nose area flattened. So I think the Cd would be somewhere in between the half-sphere and short cylinder, probaby closer to the half-sphere. Also, it would probably be easy to mold some modelling clay on the back to round it into more of a nose cone shape.