Why it’s faster to ride hard into a headwind than with a tailwind

It hurts our heads, but we’ve (finally) got an answer to this conundrum

Is it faster to push hard when the riding is easy, or when the going gets tough? Should you expend extra watts when you’ve got a strong tailwind (or a long downhill), or when you’re battling a stubborn headwind? The answer may surprise you…

This very question came up during our recent David Millar TT System training series, when the former Commonwealth Games TT champ said: “The simplest way of looking at this is that you get more bang for your buck (or seconds per watt of output) when going slower than when going faster. 

"Therefore, it makes sense to make a little more effort when you are going slowest (uphill or headwind) and a little less when going fastest (downhill or tailwind)."

A reader quickly pointed out that air resistance increases exponentially. Therefore, if you’re riding with a tailwind then you’re already battling less air resistance but travelling at a faster ground speed. This is undoubtedly correct, but fails to account for one crucial factor.

Read on for Millar’s explanation, followed by the thoughts of two prominent cycling coaches, then our own interpretation of what's going on.

Millar’s advice on pacing your efforts

David Millar, 2010 Commonwealth Games TT champion

To demonstrate his point, Millar referred to the Delhi Commonwealth Games back in 2010, when he beat Movistar’s Alex Dowsett to gold. This was an out-and-back course with almost zero change in wind direction or strength, so there was a massive tailwind on the way out, and a block headwind on the way back.

Millar remembers that he averaged around 395 watts on the way out, travelling at something like 57 kph with the tailwind. He was 3 seconds clear of Dowsett at the 20km turnaround point, then managed to average 450 watts for the way back (into the headwind) and an average speed in the range of 40-45 kph.

The end result? By going harder into the headwind on the way back, Millar put another 52 seconds into Dowsett and won by 55 seconds. "I spoke to Alex afterwards," says Millar. "His idea had been to go hard with the tailwind and survive the headwind, he probably had a pretty even power curve (read horizontal line) for the duration. That wasn’t the fastest way to ride it.

"Economise at speed, go relatively harder when it’s heavy going," concludes Millar.

It's not the person who goes fastest who wins

Graeme obree, former hour record holder:
Graeme obree, former hour record holder:

Graeme Obree, 'The Flying Scotsman'

We were struggling to understand it at this point, so we asked two coaches linked to our stablemate magazines to offer their thoughts: Joe Beer, a former 220 Triathlon coach of the year, and Nik Cook, who contributes to Cycling Plus among other esteemed publications.

Beer begins by mentioning time trial legend Graeme Obree. The former Hour Record holder has previously said that it’s not the person who goes the fastest who wins, but the person who slows down the least. In other words, keep your average speed up throughout, rather than peaking on some sections and stalling on others.

"With experience you can ride hard when the course is going to slow you down, but still maintain fast speeds on the ‘easy’ sections," says Beer. "Time trialling is never about riding at an average effort throughout, but actually knowing when to push into the red zone. Experience therefore counts for a lot."

Push your hardest when you're going slowest

Remember that you won't be spending the same amount of time on the fast and the slow sections:
Remember that you won't be spending the same amount of time on the fast and the slow sections:

Nik Cook concurs: "Yep, 100% agree... Push hard when it's hard and recover when it's easy. The biggest limiting factor to cycling speed is drag and, the faster you're going, the more drag you create. So, on a fast section of road, to increase your speed from 40 to 45 kph may take an extra 100 watts. 

"On a climb however, to increase your speed from 15 to 20 kph, the same 5 kph increase, might only require 50 watts of extra power as, at the comparatively slower speed, the effect of drag is less. So, over an entire time trial, to achieve the best average speed, it makes sense to push your hardest when you're going slowest."

The BikeRadar explanation

Contrary to what many people think, expending extra energy on the tough sections is actually faster:
Contrary to what many people think, expending extra energy on the tough sections is actually faster:

Okay, so two top coaches and a former Commonwealth Games champ all agree that you should be pushing hard into the headwinds and easing off a little when the going's easier. Still struggling to understand the reasons why? Let us take a crack at explaining it…

Imagine you’ve got a 20km out-and-back time trial, with a 20kph headwind on the way out and a 20kph tailwind on the way back. The important thing to remember in this scenario is that you won’t be spending the same amount of time on these two segments. You’ll be going much slower on the way out (into a headwind), so you could be on this section nearly twice as long.

Therefore, it makes sense to spend as little time as possible on the slower section, by getting your average speed up. In other words, expend extra watts of energy on this section. Any gains you make here will be magnified, because you’re spending more time on it.

This article was published by BikeRadar, the world's leading source of bike reviews, gear reviews, riding advice and route information
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