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Speed vs Power

I used one of these wattage calculators to compute the speed (miles per hour) vs power (watts) to maintain that speed.

The relationship is highly non-linear (cubic). This leads to a few generalized conclusions:

  • Once over 20 mph, over-efforting to go just a little faster result in diminishing returns: much higher wattage to go marginally faster; most power is going into wind resistance.
  • While ascending a steep slope, speeds are low and thus over-efforting translates almost directly into increased speed proportional to increased effort (low wind resistance).

In short, pushing 10% harder on a steep climb will result in nearly a 10% speed increase uphill. But pushing ~10% harder at 25 mph results in only a 4% increase in speed to 26 mph.

This simple idea translates directly into race strategy especially: go extra hard uphill, rest downhill, go moderate on the flats (and draft whenever possible). But there’s a twist: drop your competitors on a climb and then miss a drafting group by soloing out in front not a net gain (you’ll be caught)!

See also:

My reams of training data over the years validates the idea that climbing weight matters more than aerodynamics in climbing intensive races. Drafting (a key race strategy) nullifies any aero advantage on the flats (aero bars are prohibited also). As for descents, the gains are marginal compared to climbing (easily observed vs other riders even those on aero bikes), and the super steep descents in the Sierra are perilous under some wind conditions, so I reduce speed intentionally anyway. And the rest of the race, it’s steep climbing.

Speed (MPH) vs power (watts)

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