Wind tunnel tests: TOUR looks back at the beginnings 10 years ago and into the future
Julian Schultz
· 17.03.2022
Ernst Pfeiffer openly admits that he had little interest in cycling for a long time. But after Jan Ullrich's victory at the Tour de France 25 years ago, the operator of the GST wind tunnel was also infected and followed the magenta-coloured jerseys around the world on his TV at home. Above all, however, the businessman saw a new field of activity in the emerging cycling boom. "We could build a test rig for bicycles in the wind tunnel," Pfeiffer recalls his thoughts. As a long-time employee of the aerospace company Dornier, he had the relevant expertise.
The necessary infrastructure had been available to him since the early 1990s, when he and two colleagues took over the former Dornier wind tunnel in Immenstaad on Lake Constance under the umbrella of the Gesellschaft für Strömungsmesstechnik (GST). No sooner said than done. But how do you make a wind tunnel, which until then had mainly been used to aerodynamically optimise aircraft, appealing to bicycle manufacturers? Hardly imaginable today, Pfeiffer tried it with a newspaper advert - and was successful, because TOUR also took notice. A close co-operation was born.
More than 350 racing bikes in the wind tunnel
For ten years now, TOUR has been testing competition and aero racing bikes in the GST wind tunnel, which is hidden away in a dreary flat building on the Airbus site in Immenstaad. Since then, the TOUR testers have allowed the wind to flow around around 350 racing bikes to determine their aerodynamic quality. Wheels, helmets and time trial suits have also been tested there. The measurement protocol, which TOUR test engineer Robert Kühnen developed together with Ernst Pfeiffer, still sets the global standard for aerodynamic tests of bicycles today. No other road bike magazine puts more effort into testing competition road bikes. And for good reason: aerodynamic drag is the greatest driving resistance at speeds of 18 km/h and above. If you have an aerodynamic racing bike under the saddle, you will reach the finish line faster (see graphic).
Robert Kühnen had already seen many wind tunnels from the inside, but when he discovered the advert and carried out his first tests on Lake Constance, he was immediately convinced: "Immenstaad instead of Dresden." TOUR had previously carried out wind tunnel measurements in Dresden. "The GST wind tunnel offers ideal conditions. Nowhere else could we test as precisely, as quickly and with such high reproducibility as at Ernst Pfeiffer," says Robert Kühnen, explaining the decision to switch. In figures: For each racing bike, 130 individual values are determined at an approach speed of 45 km/h over an angle range of -20 to +20 degrees. This product of the cW value and the surface area exposed to the flow is evaluated at 41 measuring points and summarised to a resistance figure in watts, which is used in the TOUR evaluation of competition racing bikes and Aero racing bikes accounts for one fifth of the overall grade.
45 km/h? Many amateur athletes have already criticised this as impractical. Aero specialist Kühnen explains: "The test speed resolves the measurements better and makes the result more accurate. And for the Professional racing speed is definitely relevant." The engineer also adds: "In the same wind, slower riders experience more diagonal flow than faster ones. This leads to the paradoxical situation that slower riders can derive the greatest benefit from aerodynamic material because its advantage increases with diagonal flow."
The tester without upper body
Between the first wind tunnel measurement in October 2012 and today, it's not just the road bikes that have continued to evolve. TOUR has also repeatedly adapted the test procedure. In particular, the introduction of the dummy with rotating legs and no torso - previously a mannequin covered in fibreglass sat on the wheels - significantly improved the measurement quality and produced more realistic results. The test rider without a torso, with fibreglass skin, aluminium bones and hip joints made from Hollowtech bottom brackets, saw the light of day in Kühnen's workshop. He dispensed with the upper body "as it interacts little with the frame from an aerodynamic point of view, but is a source of error". A rider made of flesh and blood is out of the question, as their stamina and consistent posture would inevitably be lost with up to 20 measurements of 10 minutes each on a test day.
One daring TOUR tester nevertheless took part in the experiment when measuring one-piece racing suits - and brought home a souvenir: the flu. "With the thin fabric, he had to go into the wind tunnel at minus two degrees," says Pfeiffer with a grin. He usually receives the TOUR testers in the winter months. In the high season between May and September, it is now almost impossible to get an appointment. "When I built the test stand, I already knew that cyclists would also go into the wind tunnel. But I never expected it to become such a hype," says the graduate engineer.
Meeting point of the racing bike world
Renowned bike manufacturers from all over the world and professional triathletes such as Jan Frodeno have long since been meeting in the GST wind tunnel. "Inspired by the first measurement by TOUR, we have been testing in Immenstaad since November 2012," says Michael Adomeit, developer at Canyon. Giant, the largest bicycle manufacturer in the world, followed suit a few years later with Head of Development Andreas Wollny and has also been researching the aerodynamic quality of racing bikes and components on the shores of Lake Constance ever since. The result is aero racing bikes such as the new Giant Propel.
Around 35 watts currently distinguish a very fast bike from a slow one; however, since almost all racing bikes have been developed with aerodynamic aspects in mind, the power density is extremely high. Nevertheless, there are outliers - both upwards and downwards. "Big surprises have been rather rare recently," says TOUR test director Jens Klötzer, "but the Trek Madone from 2015 impressed me because it was remarkably fast, despite its unusual design language at the time." The current list of the best production bikes is led by the Simplon Pride II It is the only bike so far to break the 200 watt sound barrier in the TOUR test (TOUR 2/2022).
A value that will be cracked even more often in the future? Opinions differ on this. "There will be one or two niche products that will look a little different due to the current UCI regulations and will perhaps be under 200 watts. But these racing bikes will be heavier," predicts Andreas Wollny. Ernst Pfeiffer disagrees: "Current racing bikes are already extremely sophisticated, but they could be five to seven watts faster," he surmises. Who knows - the wind tunnel operator already proved to have a good feel for the future ten years ago.
10 years of wind tunnel history
2012 - October - First preliminary test with Canyon F8 (2010) as reference bike
December - First test of complete wheels with full-body dummy and test driver
2013 - March - First test of wheels and time trial bikes; introduction of the leg dummy
December - First test of aero racing bikes
2014 - May - First aero helmet test
November - New test setup: Road bikes are now measured in their standard condition, including handlebars and wheelset
2015 - November - New rating system: competition bikes, marathon bikes and gravel bikes are rated differently according to their intended use; aerodynamics of competition bikes become part of the overall rating (20 per cent)
2017 - February - Conversion to Canyon Ultimate Disc as reference bike
2018 - April - First test of racing suits
2021 - October - Simplon Pride II is the first road bike to break the 200 watt sound barrier
Wind tunnel - The fastest production bikes in the TOUR test
199 watts - Simplon Pride II Dura-Ace Di2 (TOUR 2/2022)
201 watts - Storck Aerfast.4 Pro Disc Red eTap AXS 1x12 (TOUR 2/2022)
202 watts - Canyon Aeroad CFR Di2 (TOUR 11/2020)
203 watts - Cannondale SystemSix Hi-Mod Dura-Ace Di2 (TOUR 1/2019)
204 watts - Canyon Aeroad CFR Disc MVDP (TOUR 7/2022)
205 watts - Cervélo S5 Red eTap Disc (TOUR 1/2019)
206 watts - Canyon Aeroad CF SL 8 (TOUR 7/2022), Factor One (TOUR 8/2020), Scott Foil Ultimate (TOUR 9/2022)
207 watts - Stevens Arcalis (TOUR 9/2021)
Julian Schultz
Editor
