What is the keirin, and what is the motorbike for?
B · Beginner · The track and the sprint events · 3 of 8Up to seven riders line up behind a motorised pacer, which takes them from 30 to 50 kilometres an hour. Nobody may pass it. With three laps to go on a 250 metre track the pacer swings off and the riders sprint to the line. The first across wins.
How it works
- The idea: riders "compete in a sprint after completing a number of laps behind a motorized pacer".
- When the pacer leaves: with three laps to go on a 250 metre track, or about 750 metres from the finish on other tracks.
- Half and half: the laps behind the pacer equal the laps without it.
- The pacer's speed: from 30 kilometres an hour, rising gradually to 50 by the time it leaves.
- The start: positions by lot. Riders are held side by side on the pursuit line and go when the pacer approaches.
- The first lap: riders must take the positions they drew for at least the first lap, or the race is stopped and they are disqualified.
- Behind the pacer: riders "shall remain immediately behind the pacer" until it leaves the track.
- Passing it: a rider whose front wheel passes the front of the pacer's wheel before it leaves is disqualified, and the race is rerun without them.
- The sprint: run under the sprint rules, including the sprinters' lane.
- The rounds: heats, repechages and semi-finals lead to a final for places 1 to 6 and another for 7 to 12.
- Mishaps: a restart only for a recognised mishap in the first half-lap.
The glossary has the keirin, the derny, the sprinters' lane and the sprint.
Tricky cases
Can a rider overtake the pacer to get a head start?
No. Passing the front of the pacer's wheel before it leaves the track means disqualification and a rerun without that rider.
Can riders swap places behind the pacer?
Yes, after the first lap. They must hold their drawn positions for at least the first lap, and must stay behind the pacer throughout.
A rider punctures two laps into the race. Is it restarted?
No. A restart is given only for a recognised mishap in the first half-lap.
Is the pacer always a motorbike?
It depends on the event. The rule says a "motorized pacer". The small pacing bike is commonly called a derny, and electric ones are also used.
Why the rule exists
The pacer delivers every rider to the last three laps at the same speed, so the race is about position and timing and not about who leads out. It came from Japanese racing, where it is a betting sport. The fixed starting positions and the ban on passing the pacer keep the build-up orderly.
Where it differs
| Where | What changes | Source |
|---|---|---|
| 250 metre track | The pacer leaves with three laps to go | UCI 3.2.134 |
| Other tracks | The pacer leaves nearest to 750 metres from the finish | UCI 3.2.134 |
| Olympic Games and world championships | 30 riders, with quarter-finals | UCI 3.2.135 |
| Sprint | Two riders, no pacer | UCI 3.2.029 |
From the rule book
Union Cycliste Internationale, Cycling Regulations, Part 3: Track Races (amendments applying 1 January 2026), articles 3.2.134 to 3.2.143bis. Checked 14 October 2026. Official document: UCI Cycling Regulations, Part 3 (PDF).