Motorbikes driving alongside riders increases aerodynamic drag by up to 10 per cent, according to study

A new study has shown that a motorbike driving alongside a rider increases the cyclists' aerodynamic drag by up to 10 per cent.

Researchers at the University of Eindhoven in the Netherlands knew how motorcycles in front of riders substantially reduced drag but wanted to find out how other moto positions affected the aerodynamics, so tested 32 different parallel and staggered cyclist-motorcycle arrangements.

Among their findings was that in a side-by-side arrangement and at a distance of between one to two metres, the rider's drag increased by between five to 10 per cent.

Of the other staggered positions tested, only two per cent of them led to a decrease of drag, showing that motos are more likely to be a hindrance rather than a help.

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To come to their conclusions, the researchers used the cyclist's power model to convert the drag changes into potential time gains or losses, discovering that compared to a rider travelling at 46.8km/h alone and in calm weather, a drag increase of 10 per cent resulted in a loss of 2.16 seconds per kilometre.

The tests were performed on quarter-scale models of a cyclist and a motorbike carrying two people - replicating the driver and camera operator duo that is pervasive during televised races.

If a rider is making a solo effort for victory, a situation in which they would most likely be accompanied by a motorbike camera, this could result in them losing a maximum of 21 seconds over a 10-kilometre period if the moto stayed alongside them for the duration of that distance.

This study is believed to be the first of its kind, the only similar one having looked into the drag effect of two cyclists riding side-by-side.

With a lateral separation of 0.5m between two riders, drag increased by six per cent, with any increase negligible with lateral separation greater than 1.5m. It was also found that when two riders relay, taking turns on the front, the leading rider's drag increases as the overtaking rider begins to overtake, but that once the overtaking rider moves ahead both riders' drag decreases.