Originally Posted by are39:
Actually, it depends on where the dimples are at. They need to be placed prior to the boundary layer seperation point. A golfball has them all over since a golf ball spins, and you don't know which part will be the point of attack when. The dimples cause the boundary layer to stay attached longer, thus reducing drag. Did you ever see the 'slice proof' golf ball? They filled in a certain portion of the dimples on the ball, the remaining dimples would cause the ball to right itself during flight, and go straight. Anyway, anything out away from the car body will help cause boundary seperation and induce drag which of course is bad for fuel mileage.
not true.. Myth busters did a show on this.. they used clay on the whole car, and dimpled the whole car.. both before the clay and after the clay and then after the dimples on the car.. The car with the clay and dimples actually got better gas mileage than the regular car minus all the weight from clay.. so if it is dimpled all over, you will get better gas mileage plain and simple.. so bring the hail, now im not sure how deep the dimples have to be before you start gaining anything.. it was a good amount they gained if memory serves right..