What is the Derny bike for in the Keirin? What are the rules for riders behind at the 2026 Glasgow Commonwealth Games?
Published 02/08/2026 at 13:27 GMT+1
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The Keirin is one of the most explosive and dramatic races in competitive track cycling, but it is not always clear how the competition works. We explain the key rules, and the function of the Derny bike.
What is the derny bike for? The track cycling oddity in the keirin explained
Video credit: TNT Sports
This year’s Commonwealth Games at Glasgow comes hot on the heels of the conclusion of the Tour de France, and while pacers have their own use in road races, on the track they have an entirely different function.
The Keirin forms part of the backbone of traditional track cycling, with Six Day Cycling featuring the event. Here is TNT Sports' guide to how things work.
The pacer in Keirin racing
In track cycling’s Keirin discipline, six riders line up on a velodrome to compete over a distance of six laps (1.5 km on a standard 250m track).
For the first half of the race, the pace is set by a neutral motorbike driver, traditionally riding a small motorised bicycle known as a Derny, though modern international competitions often use electric motorbikes.
The pacer's function is structural: it accelerates the field to a high base speed without forcing any single rider to expend energy, breaking the wind, setting up the final sprint under controlled conditions.
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Speed progression
Before the start, riders draw lots to determine their starting positions behind the pacer.
When the race begins, the bike enters the track and takes the lead, with the cyclists lining up directly behind it to utilise its slipstream.
Over the first three laps (750 metres), the pacer systematically increases the tempo:
- Men's events: Starts at 30 km/h and accelerates to 50 km/h.
- Women's events: Starts at 28 km/h and accelerates to 45 km/h.
By remaining close behind the pacer, riders minimise aerodynamic drag, allowing them to reserve maximum physical effort for the concluding laps.
Regulations and positioning
The pacer acts strictly as an official speed controller. Riders must remain behind the pacer's front wheel; passing the pacer before it exits results in immediate disqualification.
While passing the lead vehicle is prohibited, jockeying for position within the line is permitted.
Competitors manoeuvre to secure the most advantageous drafting position - typically second or third wheel - to minimise energy expenditure while maintaining a strong line of sight for the sprint phase.
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The release
With three laps remaining (750 metres to the finish line), the pacer reaches their target speed, signals to the field, and pulls off the track onto the apron.
Once the lead vehicle exits, the restriction on passing ends. The riders immediately take full wind resistance and sprint for the finish line, routinely reaching speeds in excess of 70 km/h over the final three laps.
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