Eindhoven University of Technology

The Unseen Propulsive Force in Pro Cycling Motor doping usually conjures up images of hidden frame motors and illicit mechanical advantages. Yet, a far more pervasive, entirely legal form of mechanical assistance operates in plain sight. Every major professional road race features a massive caravan of official vehicles. Over 100 media, medical, and support motorbikes track the peloton at the Tour de France. While these vehicles are necessary to broadcast the race, they generate massive wake fields. This slipstream gives trailing riders an extreme, unintended aerodynamic advantage. Real-World Aerodynamic Testing To measure this physical advantage, presenters Dan Lloyd and Simon Richardson conducted a field experiment on a flat three-kilometer stretch of road. They established a baseline speed of 43 km/h—matching the blistering average speed of Tadej Pogačar during his historic Tour de France campaign. Using a control run in clean air, they compared the power output required to maintain this speed against runs drafted behind a leading vehicle at distances of five, ten, and twenty meters. The Direct Drafting Advantage At a tight five-meter distance, the physical relief was immediate and overwhelming. Richardson saved a massive 28% in power output, while Lloyd recorded a 15% reduction. While holding a five-meter gap over long distances is rare, it frequently occurs through tight corners or during immediate counter-attacks before a motorbike can accelerate out of the way. Extended Wake Benefits Even when the distance increased, the drag reduction remained highly potent. At ten meters, the power savings ranged between 6.5% and 14.4%. At a highly realistic twenty-meter follow distance, Richardson still experienced an 8% drop in required power, proving that the pocket of low pressure behind a vehicle extends far further than most casual observers realize. What the Wind Tunnel Confirms These real-world findings align perfectly with rigorous laboratory data. A landmark 2020 study led by Bert Blocken at Eindhoven University of Technology used wind tunnel testing and computational fluid dynamics to study the phenomenon. Bert Blocken discovered that a single lead motorbike offers a 23% drag reduction at ten meters, translating to a time saving of over five seconds per kilometer. Astoundingly, the aerodynamic help persists even at fifty meters, where riders still enjoy a 7% reduction in drag. Implications for Race Fair Play While rules dictate that official vehicles must not allow riders to benefit from their slipstream, enforcement is highly complex. Photographers and camera crews must get close to deliver high-quality images. However, when a high-profile rider attacks, they attract a fleet of press vehicles, compounding the drafting effect. This creates an unfair advantage for elite solo breakaway specialists compared to a chasing group, potentially altering the outcomes of Grand Tour stages.