The same watts. More speed. Measured.
A field aero test for time trial, triathlon, duathlon and gravel. Your drag measured on the road, in your race position, change by change.
CdA: the number that turns watts into speed.
CdA is how much air you push. Lower it, and the same power buys more km/h.
An aero sensor on the bars reads air speed through a pitot tube, air pressure and acceleration. Your power meter reads watts. Take away what the gradient, the tyres and any speeding up cost, and what is left is the power spent on the air. With air speed and air density, that gives your CdA, second by second.
I cross-check your power against a second meter. On my own tests the two agreed within 0.75 to 1.4%, so power is not where the noise comes from.
Goal first
Your race, its distance and how long you must hold the position. A position you cannot hold is not fast.
Baseline
Repeat runs in opposite directions on a flat road near Zug, so the wind cancels out. Only steady seconds count: no braking, no surges.
Noise floor
I repeat a lap with nothing changed. On my own bike, two identical laps differed by up to 0.025 m². One lap against one lap cannot show a smaller gain. Hundreds of steady seconds per set-up, with a confidence interval, can.
One change at a time
Each change is tested on the road, never judged by eye. You get the change list and the gain of every run in your report.
Report
Your CdA with a range, watts saved at race speed, time saved on your course, and your final set-up written down so you can rebuild it after travel.
My own road bike, before King of the Lake.
I test everything on myself first: here my road bike, for the road bike class at King of the Lake. Run 1, the baseline: CdA 0.280 m². Run 2: 0.266. Run 3: 0.263. Run 4: 0.246 m², 38 W saved at 45 km/h.
What I changed stays in your report. What you see here is what it was worth. And the report keeps the failures too: a wrong first estimate, a sensor drop-out, a test order that cannot fully separate its steps. You get the same honesty.
A time trial rider.
The position was built with me on the road, one tested change at a time. Then it was measured, every run in order. Not every change helps: run 8 cost 2.5 W. The best, run 10, went from 0.180 m² to 0.174: 7.1 W saved at 45 km/h, for the same effort.
| Rider | Result | Saved |
|---|---|---|
| Thomas LecomteRoad bike, field test | CdA 0.280 → 0.246 m²Four runs, field-measured | 38 Wat 45 km/h |
| Time trial riderElite | CdA 0.180 → 0.174 m²Position built on the road | 7.1 Wat 45 km/h |
| Rider 1Time trial, field test | CdA 0.218 → 0.207 m²Same day, same bike | 12.3 Wat 45 km/h |
| Rider 2Time trial, field test | CdA 0.228 → 0.221 m²Same day, same bike | 7.8 Wat 45 km/h |
| Rider 3Time trial, field test | CdA 0.236 → 0.232 m²Same day, same bike | 4.5 Wat 45 km/h |
| DuathleteLong distance, age-group vice world champion | One aero sessionBest ever 1-hour split, 2nd at Powerman Zofingen | 31 Wat 45 km/h (25 W at 42 km/h) |
“I did not think the extensions could be extended any more, but Thomas found a solution and opened up my way too crunched position. In September 2023 at Powerman Zofingen I rode my best ever 1-hour bike split in this position and finished second.”
DuathleteLong distance, age-group vice world champion
“The aero fitting was an important part of my preparation for my Swiss time trial title. We found a fast and, above all, more comfortable position, and his knowledge of equipment gave us real gains from swapping components. Looking forward to more nerd sessions.”
Noah BögliSwiss time trial champion, Elite National category. Two European medals on the track, team pursuit. Translated from German.
One test, one written report. Final price, no extras.
- About 3 hours on a flat loop near Zug
- Bring your race bike, kit, the helmets you want to compare, and a working power meter
- Wet or very windy days are moved, at no cost
- Coaching clients: the result goes straight into your race plans
- Racing a season? Ask about coaching on the day