Bicycle Aerodynamics
Bicycle Aerodynamics - Position
- Bicycle is responsible for 20-35% of drag.
- Loose Clothing increases drag by up to 30%.
- Positions
- Goals: reduce frontal area & reduce drag coefficient
| CD | Frontal Area | CDA | Power to Overcome Drag |
Tops | 1.15 | .55 m2 | .632 m2 | 345 W |
Hoods | 1.0 | .40 m2 | .40 m2 | 220 W |
Drops | .88 | .36 m2 | .32 m2 | 176 W |
- Rearward vs. Forward position (23.57 – 22.28 N drag)
- Forward seat position decreases drag at the expense of comfort and pedaling mechanics
- Union Cycliste Internationale limits the fore-aft position of the saddle requiring it be at least
5 cm behind the bottom bracket spindle- Injury preventive measure
- Drafting
- Traveling close behind another rider
- Broken up air vortices propel second rider
- Offers advantage to both front and rear rider
- Riders in group expend 40% less energy than solo riders
Drag coefficients of two circular cylinders, one placed behind the other.
- No advantage to side by side drafting
Aerodynamic interference of two side by side struts.
Bicycle Aerodynamics -Crosswinds
- Aerodynamic drag is usually calculated assuming calm weather
- Crosswinds create aerodynamic moments and instability
- CP (point of action of aerodynamic forces) should be behind the CG for maximum stability