Impact of a nearby car on the drag of a cyclist

Cycling races contain a multitude of cars including team cars. During parts of the race, the cyclists can ride in close proximity of these cars. An earlier study indicated that there is a drag reduction for a cyclist by a following car. However, to the best of our knowledge, there is no information in the scientific literature about the impact of a car on cyclist drag when the cyclist is positioned either in-line behind the car or in parallel or staggered position with the car. This paper presents wind tunnel measurements and CFD simulations of cyclist drag for 29 different cyclist-car arrangements. It is shown that drafting in-line behind a car at a distance of 10 and 40 m leads to substantial drag reductions of about 20 and 7%, respectively. The staggered positions can lead to either a large drag increase up to almost 9% or a moderate drag decrease up to 1.4%. These drag changes can induce time gains or losses that go up to several seconds per kilometer, which is large enough to potentially influence the outcome of cycling races.