BREEZE BLOCKS

IT'S ONE OF THE GREAT MYSTERIES OF CYCLING: WHY DON'T TAILWINDS MAKE UP FOR HEADWINDS?

- PROF. ROSS TUCKER

IF YOU’RE EVER in The Netherlands in their early winter, look out for the Dutch Headwind Cycling Championships. Seriously!

This happens on the Oosterscheldekering storm barrier, which faces the North Sea; riders wait for a storm that registers seven or higher on the Beaufort Scale (that’s 60km/h, if you’re counting), and… off they go! Eight and a half kays, straight into it, on single-speed bikes provided by the race organisers.

The event’s been won by some well-known names (Bart Brentjens of Absa Cape Epic fame was the first winner, and is still the course record-holder, though into wind speeds of ‘only’ about 40km/h). In 2016, into a headwind of around 80km/h, it was won in 22:30 – that’s an average speed of 22.7km/h…

If those hardy (okay, crazy) cyclists could turn around, they’d benefit from a massive tailwind. But here’s the thing – no tailwind ever makes up for the time lost into the headwind. Every cyclist knows this dilemma: your gains don’t match your losses. So when you ride ‘there and back’ on a windy day, at exactly the same power output as on a still day, you can’t do it in the same time as on that still day.

WHAT A DRAG

Why is this? Well, because physics. And logic too, even if it doesn’t seem logical at first glance.

Without diving too deeply into the physics, the principle is that when you ride on a flat road, you don’t need to do any work against gravity. All your useful power is spent overcoming two forces: aerodynamic drag, and rolling resistance. When you ride into a headwind, your aerodynamic drag goes up; it goes down again when you ride with a tailwind.