Team time trial: turns, drafting and how long each turn should last

Four riders holding 300 W on average while taking turns ride at about 47.5 km/h; one rider alone at the same 300 W rides 43.3. The gain comes from drafting, but it has a price: at the front you need about 386 W, almost 30 % above the average, and that limits how long each turn can last.

How much is saved in each position?

Riding on a wheel reduces drag because the rider ahead breaks the air. For two riders very close together, simulations give around 27 % less drag for the rider behind and a small saving, a few per cent, for the rider in front too². In a line of four, the rear positions save somewhat more than second³, and in a large peloton the saving can be much larger⁴.

This article assumes a 30 % saving for second and 35 % for third and fourth. With equal turns, each rider spends a quarter of the time in each position, so their average drag is 25 % lower than riding alone.

How much power does each position take?

The gap between riding in front and behind is over 100 W. That is why a team time trial is not won on average power but on how well turns are shared: the rider in front works above critical power and spends reserve, and recovers it on the wheel.

How long should a turn last?

The W′ balance model lets you calculate it⁵. A rider with 340 W critical power and 20 kJ of W′ pulling at 420 W spends 80 joules of reserve per second. If they do not want to spend more than half of it per turn, the turn should last at most about 2 minutes; at 440 W, little more than a minute and a half. Behind, at 266 W, they rebuild reserve until their next turn.

• Shorter, more frequent turns let you ride faster at the front without emptying the reserve.
• Different riders, different turns: the rider with more critical power or more W′ can pull longer. Equal turns with riders of different level usually cost time.
• The changeover has a cost: each change breaks the line for a moment. With very short turns that cost multiplies.

Rule of thumb: turn length is set by each rider’s W′ reserve, not by the clock. Plan how much reserve each rider spends at the front and how much they recover behind.

What is known and what is not

That drafting greatly reduces drag is well measured in wind tunnels and simulation^2,3,4. What is uncertain is the exact value for each team, which depends on wheel gap, position and crosswind. Measuring each rider’s CdA alone and in line with the virtual elevation method is the way to use real values in the plan.

Frequently asked questions

How much do you save on a wheel in a team time trial?

Around 25 to 35 % less drag depending on position and the gap to the wheel ahead.

How long is a turn in a team time trial?

It depends on each rider’s W′ reserve and the power the front requires. With this article’s numbers, between a minute and a half and two minutes.