Climbing Aerodynamic Resistance

In its own way, aerodynamic resistance is as important to cycling as is gravity. It is the limiting force to speed on the flats and during descents. If there is a significant headwind or tailwind, it can significantly alter cycling performance.

Ascent cycling speeds

For the moment, let’s ignore wind speed and ask how fast do cyclists make ascents. My personal baseline is the 2.2 Rock Store climb which I made in 22 minutes. I already know that Elite cyclists make in 11 minutes. Doing the math, I am climbing at 6 mph and Elite cyclists are at 12 mph. Based on Pantini’s fastest ascent of the Alpe d’Huez, this roughly works out to 13 mph. Ignoring the issues surrounding that ride, let’s assume ascent speeds in general are 12 mph or less.

Aerodynamic Drag on Ascents

Reagan Zogby Physical Cycling

Ascent Drag has three key features:

  • Slower climbing speeds of 12 mph or less.
  • Possibility of Head and TailwInds
  • Ascent serpentine routes which tend to even out headwinds from tailwinds.

Aerodynamic drag is  depends on several factors including frontal area and positioning. This table estimates drag in lbs for cyclist speed in various positions.

First note at 12 mph, drag is between 1.02 and 1.59 lbs, and drops off depending on position and speed. We saw rolling resistance forces of the order of the order of 0.7 lbs or

But we also saw the total energy output to deal with rolling resistance is comparable to the heat energy a body gives off in a second. The bottom line is that at the speeds we are talking about and in the absence of headwinds, there is more effort required to address aerodynamic drag, but not significantly more than rolling resistance.

Dealing with Drag in Ascent Calculations

We also need to take into account the effect of the serpentine curves on long climbs. The net effect is that headwinds become tailwinds, and at various points in the climb, they can help or hurt, but in the end based on symmetry, there effects will tend to cancel out.

For this reason, ascent calculations normally choose to ignore the impact of aerodynamic drag. Our purpose in making ascent calculations is to assess the degree of difficult and our capabilities of making them, rather than making detailed calculations.

For that reason, our ascent calculations ignore aerodynamic drag during the ascent because of oscillation between tail and headwinds. The practical reality is if you are going to be making a climb, you would rather do it on a day where the winds are reasonable.