On the eve of the great start of the Tour de France in Brussels, ASO, the organizer of the race, summoned all the bikers to come along along the 3,480 km course. This time, the convocation was a little more solemn than usual. A few days earlier, the study of the Dutch aerodynamicist Bert Blocken made a lot of noise. We learn that a rider enjoys the wake of a motorcycle in proportions hitherto unsuspected athletes and bikers. A cyclist preceded by a motorcycle at 2m60 in front of him sees his resistance to the air decreased by almost half (48%). At 20 m, it decreases by 15% allowing a gain of 3.4 seconds per kilometer.
"After having presented this study to us, the organizer then asked us all to take the field and be even more attentive to the distances," says one of the bikers of the organization who wished to remain anonymous. We were not surprised because we knew that the rider could benefit from our presence. But not at that level. ASO confirms the content of the meeting. "This study shows us that we can not close our eyes," says François Lemarchand, the race director.
Abuses identified twenty years ago
The official is not alarmed by the situation considering that it is necessary to find "a balance" between the needs of a show broadcast and covered by the press thanks to the reporters on the motorcycles and fairness the race. And to take an example during the 5th stage between Saint-Dié and Colmar. "We noticed that the squad was spinning (Editor's note: then chasing behind Portuguese Rui Costa escaped). The camera was immediately asked to go behind. The squad in single file then understood all the interest to slip in the wake of the motorcycle camera, to the point of zigzagging like a snake when the bike changed course to benefit from a maximum of aerodynamic protection. "They are smart and are constantly looking for us," says Guy Andrieu, a biker for AFP who covers his 27th lap.
"We can understand that a biker can be trapped at the request of a photographer or a cameraman in search of the best shot or the perfect angle to reflect the tension of the event," admits François Lemarchand. Hence the pedagogy deployed with eight motorcycles empowered and authorized to intervene at the front of the race.
Among the brotherhood of bikers who are constantly evaluated and called to order in case of bad behavior including a video system equivalent to video refereeing football, it is estimated that the instructions are respected. "If we refer to the study even at 30 m you have an influence on the runner, says Guy Andrieu. With my photographer, we did some tests and that's for sure that we are less than 30 m away. Nothing to do with previous situations, however. "Twenty years ago, there was abuse but there was also a lot more gear," says a veteran pilot. I remember some bragging about allowing a runner to win a stage. The motorcycles took turns at several. And there is no need for scientific study! "
Huge time savings!
After Froome's not very academic downhill position or the ideal place to ride in the peloton, the pope of aerodynamics, the Dutchman Bert Blocken, has just published a few days before the start of the Tour de France in late June. study on aerodynamic windfall caused by motorcycles that precede runners.
By crossing wind tunnel tests and computer simulations with Ansys software editor, the scientist at Eindhoven University has arrived at the same results. And they surprise him by their magnitude. "A cyclist behind a motorcycle at a distance of 2.5m, 10m and 30m can reduce air resistance by 48%, 23% and 12% respectively. In a time trial situation and a speed of 54 km / h, if the bike is 30 m in front of him, this will generate a gain of 2.6 seconds per kilometer. In races where it is sometimes the seconds or the centimeters that decide who wins and who loses the race, these differences are very important and can be decisive. "
"We could introduce a rule like basketball"
Experiments and simulations conducted without wind from the front, side or rear and with a single bike speak for themselves. "We can easily see that there is not one and only motorcycle near the runners but often several, notes Thierry Marchal director of the sports branch of Ansys. Aerodynamic interactions are thus even more numerous, not to mention the presence of cars that also have an influence in this area. According to Bert Blocken and in light of his work, it is necessary to change the new rules of the UCI that date from 2017. "They are not sufficient and are not strictly applied," notes the researcher.
"The study is original and unassailable because scientifically proven. It was supposed that there was an effect of motorcycles but this time it can be quantified, stresses Frédéric Grappe, director of performance at the FDJ which already offers a solution. From now on, the rules must evolve with common sense. Of course, television and the press must continue to offer quality images and photos to the public. One could for example establish a rule as in basketball where the player can remain only a limited time in the racket. It would be the same for motorcycles around runners. "