Cd or Coefficient of drag represents the “Slipperiness” of the Bike and Rider and is a dimensionless number that relates an objects drag force to its area and speed, it ranges upwards from 0. (An object with a drag coefficient of 0 does not exist on earth).

Teardrops or wing shapes have some of the lowest drag coefficients.

Typical drag coefficients are as follows:

Shape Cd
Wing or Teardrop 0.005
Ball 0.5
Person stood upright 1.0
Flat plate face-on to airflow 1.17
Brick 2.0
Cyclist (Tops) 1.15
Cyclist (Hoods) 1.0
Cyclist (Drops) 0.88
Cyclist (Aero Bars) 0.70