Is it just me, or is the wind NEVER behind you?

[Norm]

But isn't that the important thing? A tail wind of 10 mph becomes a head wind of 10 mph if you're cycling at 20 mph in the same direction.

Possibly, yes, although I thought it worth pointing out the bleeding obvious given how un-obvious it can be to some.

I should also point out, for the same reason, that it will very seldom show anything other than a headwind, seldom over 30 degrees off the straight ahead. The wind speed in this country, away from the coast, doesn't often exceed 15mph.

 

[deptfordmarmoset]

I think it is the case that when you have a tail wind (ie the wing is blowing faster than you are cycling), then the boost given by the wing is proportional to the square of the wind's apparent velocity (ie F = k(V^2)), whereas if you're cycling into headwind, then the resistance is proportional to the cube of the wind's apparent velocity (ie F = k(V^3)) (where F = force, V is apparent velocity and k is a fiddle factor)

You know, I thought I was following your argument until you threw a violin into the equation.