How a rotating paceline changes your numbers

Most of a cyclist's power at normal road speeds goes into pushing air out of the way -- which is exactly what changes when you tuck in behind someone else.

Last updated: September 22, 2026

Drafting, in physical terms

At the speeds a road bike travels, aerodynamic drag is the dominant force you're fighting, well ahead of rolling resistance or the drivetrain. Drag scales with the square of your speed and with your CdA -- your frontal area times your drag coefficient, essentially "how much of a hole you punch in the air." Riding close behind another rider lets you sit in the pocket of already-disturbed air they've created, which cuts your effective CdA substantially without changing your position on the bike at all. Ride Planner's simulation uses a solo CdA of about 0.32m² by default; sheltered in a draft, that same rider's effective CdA drops to roughly 65% of that.

Why the rotation matters

A rotating paceline is how a group shares that benefit instead of leaving one rider stuck at the front the whole time. Riders take turns pulling for a short stretch, then peel off and drift to the back of the line, so everyone spends most of the ride sheltered and only a fraction of it doing the full-drag work at the front. A well-run rotation in a group of 8, for instance, has each rider pulling for roughly 1/8th of the time and drafting for the other 7/8ths.

How Ride Planner models it

Rather than simulating each rider's exact position in the rotation moment to moment, the paceline option computes one time-weighted average CdA: mostly the reduced, drafting-CdA, plus a smaller share at full solo CdA for the fraction of time spent on the front. For the form's own defaults -- a solo CdA of 0.32m², a group of 8, and a 35% drag reduction while drafting -- that works out to an effective CdA of about 0.22m²: roughly a 30% cut in aerodynamic drag averaged across the whole ride, compared to riding solo at the same power.

A 30% drop in drag doesn't mean 30% more speed -- drag is only one part of the total resistance, and the relationship between power and speed isn't linear -- but it's enough to meaningfully shorten the time estimate for the same target power, which is why group rides and supported tours consistently post faster average speeds than the same riders would manage solo.

What this assumes

This is an average-case number for a rotation that's actually working: roughly even pulls, a group that stays together, and riders who don't skip their turn at the front. A ragged, poorly-organized paceline, a group with a wide spread of fitness levels, or a rider who never rotates up won't see the full benefit the model assumes -- in practice their effective CdA sits somewhere between the solo and full-rotation numbers, closer to whichever end better matches how much time they actually spend sheltered.