Aerodynamics and CdA

Aerodynamics and CdA

Above 30 km/h, aerodynamics dominates cycling performance - small CdA improvements save significant power.

Understanding CdA

• CdA = Coefficient of Drag × Frontal Area
• Lower CdA = less air resistance
• Typical road position: 0.300-0.350 CdA
• Aero road position: 0.250-0.290 CdA
• Time trial position: 0.220-0.250 CdA

Power Savings from Aerodynamics

• Reducing CdA from 0.300 to 0.250 saves ~30W at 40 km/h
• Aero helmet: 5-10W savings
• Aero wheels: 10-20W savings
• Aero frame: 15-25W savings
• Optimized position: 20-40W savings

Measuring CdA

• Wind tunnel: Most accurate, expensive
• Velodrome testing: Controlled environment, accessible
• Field testing: Coast-down tests or power analysis on flat roads
• Virtual elevation method: Uses power and speed data

Optimizing Position

Drop handlebars allow multiple positions. Lower = more aero but may reduce power or comfort. Find the lowest sustainable position where you can still produce target power. Narrow arm position, flat back, and head down all improve CdA.