Courchevel drafting effect TdF Spoiler

[OnceFast]

It looks like Lance towed Valverde, Mancebo and Rasmussen most of the last 10K up the Courcheval at about 26 Km/hr. Does anybody have an idea of the energy savings the draftees experience at that speed and gradient? I thought of trying to figure this out using my Computrainer, but I don't think I can draft the pacer long enough to get an accurate reading.

[Chief]

The rule of thumb is that at 40 kmh, I believe, drafting on the flats reduces the power requirements by 25-30%. The aerodynamic drag varies as the square of the speed and power varies as the cube of the speed and depends upon the frontal area of rider/bike. Hence, assuming the same frontal area for each rider, at 25 kph drafting reduces the power requirements by (25% or 30%)*(25/40)^3 = 6 or 7%. Clearly, at typical climbing speeds the biggest portion of the power demand is getting the weight of the rider and bike up the hill and not overcoming aerodynamic drag. This power demand is the product of the gradient of the climb, weight of the biker plus bike, and the speed.

[coylifut]

and I always do, 7% is huge.