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How to cheat in a time trial

It’s all about using air, but not the way you'd think

Photo by: Sirotti
March 10, 2022
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There’s no doubt that two-time world chrono champion Filippo Ganna is one of the best testers in the sport. On Monday he demolished the time trial opener of Tirreno-Adriatico, taking the leader’s jersey, and putting out incredible numbers. Ganna set the best intermediate time with 7:17 and passed his minuteman. He would go to put ten seconds into second place rider, Remco Evenepoel (Belgium/Quick Step-Alpha Vinyl.)

In the last 2.5 km, Ganna averaged 520 watts. He averaged 59km/h, hitting 63 at one point. His max power was 670 watts.

However, as many noticed, he also had a team car following him with twelve bikes. That’s a lot of spare bikes for a 14 km time trial.

So why would a team car follow closely, stacked with spare rides? According to retired Professor Jørn Hansen from The University of Toronto Institute for Aerospace Studies, the advantage is caused by a “bow wave.” If you’ve ever stood on a subway platform when the train is arriving, you’ll know the feeling of wind coming towards you. A bow wave is the wave that forms at the bow of a ship when it moves through the water.

How to cheat in a bike race: Part 1

On land, it would refer the pressure created by an approaching car, or anything else because the air is being compressed. The positive pressure will help push the air or fluid in front of it.

So Ganna’s follow car having 12 bikes makes sense: it creates a larger surface area to push air in front of him. You often see similar tactics used when a rider is in a breakaway, and the team car follows as close as possible. (Or if there’s a crosswind, the car will ride to the side and talk to the rider, sheltering him.)

It’s said before a pro time trial that mechanics are often scrambling to put up as many bikes as possible on the car to help bolster the effects of the bow wave. Even if the gains are marginal, in hotly contested time trials where the winner may only be a second or two ahead, it all helps.

There are stories in the Tour of Italy in the old days about how the Italian press helicopter would fly lower and behind an Italian rider such as the legendary Francesco Moser, pushing him along, or, if it was a rival, fly ahead of him. By flying ahead of him the chopper would create the opposite effect, basically creating a headwind.

The lesson here? The next time you are doing your local time trial, try and convince a family member to load 12 bikes on your Minivan and then follow 10 m behind. Hello, PB!