The Keirin is one of track cycling’s delightfully eccentric events, in which riders are paced up to speed behind a special motorbike before launching their attacks from top speed in the final 600 metres. It’s a race that is dominated by sprinters and often features a little illicit roughhousing as riders jostle for position.
Keirin racing starts behind a pace bike known as a Derny. Combining a small engine with a traditional bicycle’s pedals-and-chain drivetrain, it’s capable of precisely controlled acceleration and deceleration, which makes it ideal for pacing riders up to speed. The Derny was traditionally used as a pacer in road cycling’s longer single-day events, such as the 560Km Bordeaux-Paris, but as those races fell out of favour the Derny became a fixture at track events where it’s now used to start the Keirin.
The Derny rider sits bolt upright to provide a windbreak for the following riders as the Derny gradually accelerates from a cruising speed of about 30kph up to a decidedly taxing speed of around 50kph before pulling aside two-and-a-half laps from the finish of the eight-lap race.
Not only do the riders have to keep pace with the accelerating Derny, they also have to manoeuvre for position behind it. Having been paced up to speed, Keirin riders will be able to launch incredibly fast attacks for the line once the Derny peels off. Some riders favour an immediate attack from directly behind the Derny, while cagier riders prefer to carefully time their sprint so that they can accelerate just as the riders in front start to fade.
Britain’s Becky James has two bronze and one gold medal in the Keirin from the World Championships, and will be riding in the Olympics for the first time – she considers her main rivals to be Germany and Australia, most likely represented by Kristina Vogel and Anna Meares. Jason Kenny, meanwhile, will likely find himself pitted against World Champion Joachim Eilers, and New Zealand’s Eddie Dawkins.
The Keirin heats start at 2pm on 13th August on BBC4