The latest wind-cheating lids are a common sight in the pro peloton - but does the everyday rider need one?

Until Mark Cavendish swept to victory in the 2011 World Championship road race wearing a skinsuit and adapted Specialized helmet that had its vents covered with transparent plastic, aerodynamics had been something talked about in hushed tones by nerdy time triallists.

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Suddenly aero-nerdiness was all the rage, and for good reason. Yes, drafting behind another rider requires approximately 30 per cent less power than riding out in the wind, but what if you could increase that to 36 per cent by judicious application of knowledge gained in the wind tunnel?

That would allow a sprinter like Cavendish to arrive at the finale that crucial little bit fresher than his rivals, and of course the slipperier helmet and clothing would help him outdrag the other fastmen in the dash for the line.

Mark Cavendish wins elite men's road race, Road World Championships 2011

Mark Cavendish winning the elite men’s road race, Road World Championships 2011

So exactly how much time or power could an aerodynamic helmet save? A properly-fitting time trial helmet compared to a standard road helmet is worth about a minute over 40km, according to Michael Hutchinson, multiple national time trial champion and author of Faster: The Obsession, Science and Luck Behind the World’s Fastest Cyclists. For slower riders the gains can be even bigger.

Adam Hansen escapes on stage nineteen of the 2014 Tour of Spain

Adam Hansen’s head was cool enough, but those vents were only slowing him down. Photo: Graham Watson

“A fully-vented normal helmet is the least aerodynamic thing in the world you could put on your head,” says Hutchinson. “It’s about as aerodynamic as a sombrero. It’s designed to swirl air around your head, it’s designed to create turbulence. You’re better off without a helmet at all. And you’re certainly better off with a cloth cap.”

Find the right lid for you

Aero revolution

The latest generation of aero road helmets such as the Giro Air Attack and the Specialized Evade — helmets for bunch racing that have appeared since Cavendish’s groundbreaking Worlds victory — offer a saving that is somewhere between a full time trial helmet and a vented road helmet. Giro claims the Air Attack is 17 seconds faster over 40km (ridden at around 50kph) than its 24-vent Aeon. Hutchinson, however, warns that this figure could vary depending on the shape of the individual rider and their riding position.

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He points out that the aero helmets themselves even use different approaches: “The Giro Air Attack is very, very round and the Specialized Evade is much longer,” says Hutchinson. “And they probably work differently for different people.”

Marcel Kittel wins the 2015 Peoples Choice Classic in Adelaide

Marcel Kittel wearing Team Giant Alpecin’s new aero road helmet. Photo: Graham Watson

For riders looking to reduce their aerodynamic drag in individual time trials, Hutchinson says that for him a long-tailed aerodynamic helmet is faster than a short, stubby one such as the Kask Bambino, as used by Team Sky, providing the tail sits neatly on his back. In addition, it’s crucial to be able to hold that position.

A glance down at the computer or sprockets sends the tail up into the airflow and the advantage is gone. By contrast, short-tailed helmets such as the Bambino are more forgiving. They may not be as fast in a straight line at zero degrees of yaw, but they perform better in a wider variety of positions and wind angles.

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“If you can’t find a [time trial] helmet that sits neatly on your back, you’re probably better off with something like the Bambino,” says Hutchinson.

It’s precisely because there are so many variables that aerodynamics is so fiendishly complicated. Hutchinson has spent years testing headgear, only to conclude that: “In the end I don’t feel as if I know that much about it. Aero helmets make you faster, yes, and after that the answer to everything is: ‘I don’t know, I’d need to put you in a wind tunnel’.”

Bradley Wiggins on the front for Team Sky during he opening Team Time Trial of the 2014 Tirreno-Adriatico in which they placed 6th

Team Sky have done plenty of wind tunnel work to get their aerodynamics dialled. Photo: Graham Watson

Aero road helmets: yes or no?

Our take

Clearly an aero helmet does make you faster by a measurable amount, but it’s not quite free speed because the reduced ventilation means you pay in heat build-up. When we tested the Giro Air Attack in 2013, our reviewer said: “I didn’t want to race in it once the arm-warmers came off — it was just too warm.” Unless you live in a cold climate, we would probably not recommend an aero helmet for use as your sole, everyday lid. For the occasional Sunday suicide break, however, go for it.

Yes: Michael Hutchinson, author and time trial champion

“The difference [between a standard road helmet and an aero one] is not trivial. If you want to go faster, you will go faster with an aero helmet.

“I can’t understand why anybody who has any notion of getting involved in a long breakaway in a road race wouldn’t wear an aero road helmet. You might be out there for a couple of hours and over the course of a couple of hours you might well save a couple of minutes.”

No: Jon Sharples, TrainSharp coaching

“Let’s remember Greg LeMond won the Tour by the smallest margin in history. If Laurent Fignon had also worn an aero helmet and used tri-bars Tour history could have been very different.

What about the rest of us? I often say to our riders that spending money on a light/aero piece of equipment will give a few seconds once, but you will reap the benefits of investing in your own fitness over and over again.”