Rear wings - Cosmetic or Functional

[andylinney]

Having had a good look at my two cars (B4 and B44) I can't help but wonder just how functional the huge rear wings really are.

Sure enough, at full tilt I can imagine there's enough airflow over a car to make a measurable difference but at track cornering speeds (where I'd imagine it'd be of most use) is it more of a cosmetic piece of 'man jewellery'?

I wonder if any of these cars have ever been anywhere near a windtunnel?