Aero In The Peloton
During World Tour events there’s always a lot of talk about the aero models the pros are riding. Does it really make that much of a difference since they're usually drafting?
Most people already know aerodynamics are important in an individual event – a time-trial or solo breakaway, for example. Some people don’t think aero matters when riding in a group. They’ll say: “I’m drafting, aero doesn’t matter to me.” However, even in a group, most of the retarding force you’re pedaling against is still aero drag.
Asker Jeukendrup (High-Performance Cycling, 2002) measured a 30-per-cent decrease in power required while drafting, compared to riding alone. This roughly matches the drag savings we’ve measured on the road with our on-bike instrumentation. This decrease is due only to the reduction in aero drag when drafting, as nothing else changes: mechanical friction and rolling resistance are unaffected by drafting.
Most drag-yaw charts are taken from wind-tunnel test data for a single bike, not drafting. This data is usually the source for the most commonly cited drag savings. So when you’re in a group, discount the drag savings by about 30 per cent. For example, when we say the Cervélo S5 saves 9 Watts compared to the S3 when riding alone, it means you’ll save about 6 Watts when drafting in a group.
Remember: These savings are in addition to the power saved by drafting in the first place. By sitting in the group, you already save 30 per cent – after all, that’s why we draft. For example, if you already save 90 Watts by drafting, you can save 96 Watts by riding an S5. You save 6 more Watts.