Aerodynamic Drag

Drag is the force of air resisting the motion of the bike and rider. It grows with the square of speed, and the power needed to overcome it grows roughly with the cube, so going a little faster at motorway speeds costs much more fuel.

On a motorcycle the rider is a large part of the drag. Fairings, a screen and a tucked riding position reduce it; luggage, crash bars and an upright stance increase it.

Practical effects: a big top box or panniers lower top speed and raise fuel consumption, and a badly shaped screen can create buffeting. On long trips, a well-adjusted screen reduces fatigue as much as it improves economy.