Wind Resistance is the single biggest contributor to your total drag.
Determining your specific wind drag is extremely complicated, and at best an approximation. Regardless, serious cyclists give considerable thought to their riding position and choose equipment with a specific race in mind.
CompuTrainer's exclusive adjustable Drag Factor feature improves your race preparation by recreating the exact resistance you feel on the road. While Drag Factor's default setting is sufficient for everyday fitness training, fine tuning your Drag Factor can prepare you for specific events and can help predict race day performance.
For a given watts input, a racer will get more speed by lowering frontal area.
Setting your Drag Factor is simple, and based on the repeatable correlation between your power output and heart rate.
Setting the Drag Factor:
On a flat outdoor stretch, note your heart rate while riding in your probable riding position at your expected race speed. Then replicate that speed indoors with the same gear setting in CompuTrainer's Power Training mode, and adjust your profile's Drag Factor until you've matched your outdoor heart rate.