Immersion in a day of wind tunnel testing

In modern professional cycling, the quest for performance is no longer limited to physical training or nutrition. Every detail counts, and aerodynamics plays a decisive role. When a rider is travelling at over 50 km/h, around 90% of his or her power is used to combat air resistance. Gaining a few watts can mean several seconds' advantage in a time trial... or a hard-fought victory at the finish line.

With this in mind, we travelled to Friedrichshafen, Germany, in the company of our partner Swiss Side. An invaluable partner with long experience in Formula 1, with whom we share the same demand for precision and performance.

No coincidence in the choice of location: this is one of the most advanced and rigorous wind tunnels in Europe.

There, the aim is not simply to validate existing choices, but to push the thinking further. Observe, compare, understand and, often, discover. The wind tunnel is both a validation tool and an exploration laboratory, where intuitions rub shoulders with physical reality.

The term "wind tunnel" can be misleading, since it's actually the other way around: the air isn't blown towards the rider, it's sucked in behind him. This principle generates a turbulence-free airflow. The result: the data collected is extremely stable, and the variations measured are really due to changes in the rider or his equipment.

On the ground, a precision balance records the forces exerted on the rider, and calculates his coefficient of aerodynamic drag (CdA). This figure alone sums up a rider 's ability to "split the air". The lower the CdA, the more efficient the rider . From there, we translate the CdA into aerodynamic watts, i.e. the power a rider needs to deliver just to overcome air resistance at a given speed, here simulated at 55 km/h.

Swiss Side engineer Bjorn adds: "Aero power is the power you need to develop just to overcome aerodynamic drag, but not rolling resistance, transmission friction or other losses. It's a pure, isolated figure that allows us to compare."

Tests are also carried out at different angles of incidence to simulate crosswinds, like those riders face in real-life conditions. "If we were content with a perfectly frontal wind, the data would only be valid in a velodrome," adds Paul Barratt, our Innovation Director.

Finally, to complete the force measurements, Swiss Side uses a sophisticated tool: a system of dynamic pressure sensors that pass behind the rider during testing. The aim is to understand where turbulence occurs.

"The scale tells us if there's a difference, but not where. The pressure sensor, on the other hand, creates a map of the depressions in the air just behind the rider. This shows us precisely which areas of the body or equipment generate the most drag. This is invaluable when working on helmets, textiles, or changes in rider position", explains Jean-Paul Ballard, founder of Swiss Side.

The day begins with Léo Bisiaux. This is his first wind tunnel session, and an opportunity to validate his position on the time trial bike. This had already been worked on by the performance team, and immediately proved effective, with a CdA measured at 0.179. Using this as a basis, we made a series of targeted adjustments: the inclination of the extensions was increased by five degrees, the arms were moved fifteen millimetres closer together, and the posture of the head and torso was refined. As a result of these adjustments, the CdA drops to 0.170. This corresponds to a gain of 4 watts, without compromising stability or rider comfort.

But the most memorable moment came when we tried out the new Van Rysel time trial helmet, fresh from the design office. Léo was one of the first to test it. The result is striking: an extra 11.7 watts are saved. "I thought I was going to gain a little more with the settings, but my position was already good," explains Léo. "On the other hand, the difference the helmet makes... almost 12 watts on its own, that's crazy."

Mathias Ribeiro Da Cruz, the team's innovation engineer (and also last year's French amateur time trial champion) points out that these results are very personal: "What works for Léo won't necessarily work for another rider. The aim is to build a high-performance, tenable position that's unique to each rider.

In the afternoon, it's the turn of Felix Gall, one of our leaders, to take to the stage. The aim is strategic: to optimize his equipment for the Tour de France time trial in Peyragudes. The particularity of this time trial: 3 km of false flat followed by an 8 km climb. The dilemma is a classic but complex one: should we opt for the aerodynamics of the time trial bike or the lightness of the road bike, fitted with extenders?

We test both configurations in the wind tunnel, at different speeds, recording the CdA, positions and sensations. All this data is then fed into simulation software developed by Swiss Side, capable of accurately modeling the course of a race, taking into account profile, weather, weight and equipment used. This software simulates hundreds of combinations and identifies the fastest setup for the rider 's profile and the race. It's even possible to simulate the benefits of a mid-course bike change, a daring strategy that sometimes pays off.

Felix also tests the new Van Rysel helmet, with a 10-watt gain. This helmet was developed from the dummy of Bruno Armirail, double French time trial champion. Bruno wasn't using it at the time of his last title, but had already benefited from extensive optimization work. He won by three seconds. Not much, but enough. And that's exactly what the wind tunnel allows: to transform a performance hypothesis into measurable reality.

Behind every wind tunnel session, there's a real human and technical synergy. Modern cycling is a team sport at every level. On the wind tunnel stage, around the rider pedaling in a time trial position, dozens of eyes and tools observe, analyze, measure and adjust.

Fluidity between roles is essential: Paul Barratt, innovation manager, discusses strategy with Swiss Side engineers and oversees the modifications made during the day; Mathias Ribeiro Da Cruz, innovation engineer, analyzes results in real time to adjust protocols; Gilles Martinet, mechanic, makes modifications to the bikes with precision; Alexandre Pacot, trainer and positioning specialist, checks that adaptations also respect the rider's physical capabilities. All this under the watchful eye of Van Rysel engineers Louis and Alban, and our head coach Stephen Barrett, responsible for training and race performance, who knows Felix and his abilities particularly well.

Paul is right to explain how marginal gains work: "Everyone talks about marginal gains, as if they systematically add up to a massive advantage. In reality, we test a lot of things. Most of them bring little or nothing. But sometimes, an idea has a huge impact. And that's exactly what we're looking for. The process is one of guided discovery. We start with a hypothesis, experiment, adjust. It's a testing ground."

The wind tunnel isn't just a place for measuring: it's a space for dialogue, intuition and experimentation, where each team member brings a complementary viewpoint to bear on the best possible solution.

The day's results speak for themselves. Léo gained over 15 watts between the position adjustments and the new helmet. Felix, around 10 watts. These figures, translated into seconds on a time trial, can be enough to change the standings.

But these gains only have value if they are understood and integrated by those who have to apply them: the riders themselves. That's why we always express these results in watts, a unit of measurement that speaks to them immediately. " riders know perfectly well what it means to push 20 or 30 watts more. When we tell them that a helmet makes them gain 10 watts, it's not abstract: they realize the difference," explains Paul Barratt.

Over and above the figures, the wind tunnel enables us to make technical choices, to confirm certain avenues and rule out others. It's a decision-making tool. And for us, a key element in the preparation of major events such as the Tour de France.

Every rider on the team undergoes aerodynamic testing at least once a year. The leaders go back to the factory as soon as a key element (helmet, textile, equipment, etc.) is ready for testing... It's an essential step in our approach to performance.

The wind tunnel is not a technological showcase. It's a practical, demanding and sometimes thankless tool in the field, but it's extremely effective when used properly. It allows us to test, fail, learn and then succeed. It helps us transform ideas into measurable realities. And above all, it reminds us that in this sport, every watt counts, because every second counts.

But however precious these figures may be, they are no substitute for the essential: the rider's commitment, his ability to surpass himself, to suffer, to go for that fraction of a second when his legs are burning and everything seems frozen.

We do everything in our power to ensure that our athletes have the best possible conditions, the most accurate data, the fastest equipment. But at the end of the day, it's they who turn these efforts into performance. Because no simulation, no test, can model mental strength, the will to win.

And this is undoubtedly the best part of cycling.