Aero helmets need to know
Speed, comfort, venting, safety… the key helmet concerns answered
01 Pure speed
Every brand will tell you that they’ve created the fastest helmet around, and it’s a claim that’s very hard to disprove given the array of different testing baselines available in a wind tunnel, velodrome or using CFD (Computational Fluid Dynamics). With yaw angles (the effective direction of the wind, usually measured from 0-20°), various speeds (25-45km/h is the wind-tunnel norm) and a countless array of riding positions available to be tested, it’s easy for a brand to find one area, no matter how rare (eg 55km/h at a yaw angle of 20°) and find that their helmet excels in it. What is clear, however, is that aero road helmets are faster than standard ventilated road helmets. Our previous Silverstone Sports Engineering Hub wind-tunnel time has revealed that an aero road helmet can be up to 45 seconds faster than a traditional vented lid over a 40km ride at higher speeds (35 and 45km/h). “Safety for a producer of bike helmets is paramount, but top riders need more than just safety,” says Bianca Bernardi, export manager of Limar helmets. “They need their head to become an aerodynamic advantage.”
02 Optimum position
Much of these aero gains will depend on you keeping your head still, straight and low, however, since the effectiveness of many aero helmets is reduced by having them in the wrong position – especially if they have some form of tail that can protrude into the air. Get it right, though, and you will reap the dragsaving rewards as the helmet has a major role in the aerodynamic profile of a rider (remembering that around 80% of total drag is created by the rider and 20% the bike, with the helmet’s frontal position also being a key factor in this).
Another previous windtunnel test at the (now defunct) Boardman wind tunnel also highlighted how much variation there could be between aero road helmet from rival brands.
“The range of differences in the aero performance of the helmets you’ve tested is 5.9%, which is large given that all the helmets were aero road helmets,” Boardman’s Jamie Pringle told us. “Consider that, for a normal 90-minute windtunnel-optimisation session, our typical saving in aero drag is 9-10%, but this is coming from adding up gains from a dozen changes, including bike position. That a single change of helmet can offer more than half of this total gain is remarkable.”
03 Weight matters
Speed is important, but an aero road helmet needs to offer comfort for long rides and racing – where weight is important. “Comfort comes from lightness so road cyclists can wear the helmet for many hours,” says Bianca Bernardi, Limar’s export manager.
Our helmets range from 220g to a weighty 352g, lighter than classic time-trial helmets (circa 350-405g) but a touch heftier than traditional road helmets with more ventilation channels, which can dip below the 200g mark. “It’s also about designing the right helmet for the right person. We have to factor in different lines for Caucasian and Asian riders due to different head shapes, for example” adds Bernardi.
04 Find your fit
WorldTour-proven, CFDed to within an inch of its life, hours in the wind tunnel… the helmets here are full of aero trickery, but if they don’t fit you properly or the straps are loose, you’ll soon be leaching seconds to your big ride rivals.
“A helmet’s volume can be as important as its shape and features, and helmets that fit poorly can be counterproductive,” adds Pringle. “Product development that considers multiple wind scenarios and individual fit are likely to have a greater impact in the real world.”
“Our previous wind-tunnel time revealed that an aero road helmet can be up to 45 seconds faster than a traditional vented lid over a 40km ride at higher speeds”
While trying before you buy is ideal but not always easy, aim to study the sizing charts extensively as the sizing of our helmets on test can vary markedly between the international brands. Once bought, the ratchet or retention system will secure your head into the helmet and should be easy to adjust on the move. A dial is currently the most common system on aero road helmets, but ensure it sits neatly into the back of your head. Also spend some time playing with the range of internal height adjustments and strap adjustability to ensure that you’re maximising the sizing opportunities offered by the helmet and making sure those straps sit flush to your cheeks and chin.
06 Importance of airflow
Here’s where traditional road helmets should retain the
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All of the helmets here have passed the relevant European safety tests, but also look out for added safety features such as the Multi-Directional Impact Protection System (MIPS). MIPS aims to help with rotational impacts by allowing the EPS shell to move up to 15mm over an inner liner, aiming to reduce the energy transfer that can cause concussion or more serious brain injuries. MIPS does add weight, costs more and the benefits still aren’t 100% conclusive, but recent tests by both Virginia Tech (see below) and the Road Safety Trust highlight the benefits of MIPS, so the signs are good. edge over aero road options, with Giro’s vented Aether boasting 32 ventilation channels compared to its new Eclipse Spherical’s 14, for example. And yet Giro claims that the Eclipse ‘rivals our most aggressively vented road helmets’ in terms of ventilation. Aero road helmets do this by seeking inspiration from the Venturi Effect, which is the reduction in air pressure when a fluid flows through a constricted section (in this case, the ventilation channels), ensuring that many of the helmets tested overleaf can also handle the summer mountain climbs without cooking your bonnet.
The helmet’s padding, meanwhile, should be quick to dry to stop any sweat streaming down your face, and ideally it should be antibacterial and also removable, so you can detach and wash the pads with ease.
07 Virginia Tech ratings
Virginia Tech University in the United States independently assesses helmet performance for consumers. Cycling helmets are given a rating based on their performance in a number of laboratory safety tests, aiming to replicate the forces commonly experienced by cyclists in crashes – including those most associated with concussion. The star rating given to a helmet reflects its performance in those tests, with test scores weighted on how often those sorts of impacts are experienced. Not all of the helmets in our test have been rated by Virginia Tech, but where a rating was available we have included it.
“Helmet padding should be quick to dry to stop any sweat streaming down your face, and it should be anti-bacterial”