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I understand the pace bike gets the pack up to speed, but of the 8 lap race how do they decide which lap to bring the pace bike off?

Is it based on speed?

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up vote 2 down vote accepted

It leaves at lap 5-1/2 laps at the Olympics, but it's more tied to distance. Speed plays a factor in that at the point the pacer leaves the track, they should be going 50 km/hour (or some set speed for the particular race). The pacer will always leave the track after the same distance and for a 400M velodrome, that's 5-1/2 laps.

EDIT: looking around the web, it looks like some K. races go other distances. Keirin has it's roots in Japan with paramutual betting and I get the impression that it varies a bit more in Japan than it does in the U.S.

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I don't think this is quite exactly right. The UCI regulations specify not a distance to be traveled but rather the distance remaining: no matter the length of the track, the pacer pulls off between 600 and 700 meters before the finish line. Thus, if the track is 250 meters long the pacer pulls off about 2.5 laps before the finish; if the track is 333 meters long the pacer pulls off 2 laps before the finish; and if the track is 400 meters long the pacer pulls off 1.5 laps before the finish. – R. Chung Aug 5 '12 at 17:20
@R.Chung, you are correct. Please put that in a separate answer. All UCI rules are available on (contains UCI rules for all types of races, road & track, in excruciating detail). – Angelo Aug 6 '12 at 12:33

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