Aero vs vented helmet: which one for the road?

Vented helmet vs aero shell: two design approaches

To judge a vented helmet, check whether its front vents lead into internal channels and rear exhausts. An aero helmet has vents too, but its shape is drawn first to reduce drag.

On the Comete Ultimate aero helmet, every dimension of the shell was refined in the wind tunnel and with CFD simulations: this is the AeroShape design. AeroFlow disruptors speed up the air just before it separates from the shell. The airflow stays attached to the helmet for longer, the low-pressure zone at the back shrinks, and drag drops with it. At the same speed, you need fewer watts.

On the Comete SL road helmet, the front vents are connected to internal ventilation channels. The airflow cools your head, then leaves through the rear openings, carrying moisture with it. The helmet's shape, developed for aerodynamics, was tested in the HEPIA wind tunnel in Geneva.

Helmet aerodynamic gain: speed, position and watts

A helmet's aerodynamic gain is measured in watts, for a given speed, rider position and wind angle. During the development of the Comete Ultimate aero helmet, its drag was measured in the HEPIA wind tunnel in Geneva, at 50 km/h, with a rider, in two positions and at yaw angles of 0°, 10° and 20°. The tests take place in a controlled environment with stable atmospheric conditions. No gain is published at a lower speed.

In the upright position, where riders spend most of their time, the Comete Ultimate helmet saves 9 W on average against the helmets in the test panel. In the aero position, it saves up to 7.5 W against its closest competitor. Riders spend only a minority of their time in that position, and the helmet was optimised for both.

To compare two aero road helmets, note for each one the test speed, the rider's position, the yaw angle and the reference helmet. A gain against the closest competitor and an average against a panel of helmets do not measure the same thing. If any of these four details is missing or differs between two models, the figures cannot be compared.

Aero helmet ventilation in summer and in the mountains

Aero helmet ventilation on the Comete Ultimate relies on the AirChannel system, optimised with CFD to improve cooling inside the helmet. Air comes in through large front vents, flows through deep internal channels and leaves through the rear exhausts.

On a climb, you ride far slower than during the wind tunnel tests. The power needed to overcome drag rises very quickly with speed, and uphill an aero helmet gains you very little. At low speed and under hard effort, your comfort depends mostly on the fresh air coming into the helmet and on sweat management. On the Aksium road helmet, quick-drying Coolmax pads add to the ventilation.

The Comete Ultimate helmet, the Comete SL road helmet and the Aksium helmet all have a slot for your glasses on a climb or during a stop, so you do not have to hook them on your jersey or hold them. On the Comete SL and Aksium helmets, this storage is called Glass Garage, one of Mavic's cycling helmet innovations. The Comete Ultimate helmet has adjustable straps that work with glasses.

Which Mavic road helmet, from most aero to most versatile

The Comete Ultimate aero helmet weighs 20 g more than the Comete SL road helmet in size M, and both use the same RS360 retention system. It keeps the Comete Ultimate helmet in place, even at high speed.

Model	Weight (size M)	Sizes	Protection	Retention	Recommended use	Price
Comete Ultimate road helmet	300 g	S, M, L	Mips Air Node Pro	RS360	fast road riding, racing	€239.00
Comete SL road helmet	280 g	S, M, L	MIPS, extended rear coverage	RS360, FidLock buckle	road and gravel	€159.00
Aksium road helmet	not stated for these sizes	S/M, L	extended rear coverage	adjustable fit	road, commuting, gravel	€59.00

The Aksium road helmet costs €180 less than the Comete Ultimate helmet, and the Comete SL helmet €80 less. The reflective zones on the sides and rear of the Comete SL helmet make you more visible in low light.

If you also ride on trails, all three models are part of Mavic's gravel helmet selection. All three come with a 2-year warranty. The Aksium helmet comes in only two sizes, S/M and L, so try it on before you buy if you are between the two.

How to choose your aero or vented helmet

To choose your aero or vented helmet, start from the pace of the rides you do most often. For racing or fast group rides on flat, fast courses, choose the Comete Ultimate aero helmet. If your rides alternate between road and gravel, choose the Comete SL road helmet; if commuting comes into it too, the Aksium road helmet. For long climbs in summer, compare ventilation and padding first.

All three road helmets are listed with their prices in Mavic's range of road bike helmets. For mountain biking the criteria change: see the mountain bike helmet buying guide.

FAQ: aerodynamics and ventilation of a road helmet

An aero helmet in summer should be judged on its padding and sweat management as much as on its vents. On the Comete Ultimate aero helmet, dedicated sweat channels keep moisture away from the forehead and eyes, and the Mips Air Node Pro system is paired with Coolmax padding that improves moisture management. The Comete SL road helmet has XRD memory foam at the forehead for comfort. For summer riding, compare these pads and channels from one model to the next, as well as the number and size of the vents.

An aero road helmet is allowed in all road events only if it falls into the traditional helmet category of the UCI regulations; the time trial helmet is reserved for individual and team time trials. A traditional helmet has at least three separate air vents on the shell, leaves the ears uncovered and has no visor. The time trial helmet has none of these restrictions. Both categories share the same maximum dimensions, 450 mm long, 300 mm wide and 210 mm high, accessories included. No removable cover or tape may be added, apart from accessories supplied by the manufacturer. The Comete Ultimate aero helmet complies with UCI regulations.

An aero helmet for gravel makes sense as soon as the ride becomes a race. Thomas De Gendt, supported by Mavic in his road and gravel projects, puts it this way: “Performance in gravel is getting more important each year with a healthy focus on aerodynamics. A fast aero helmet saves us some important watts to get us fresher into the final.” On a slow or technical course, where the pace stays low, the Comete SL road helmet is better suited to mixed use.

Over a 50 km race, the Comete Ultimate aero helmet can save you up to 11 seconds against its closest competitor. This figure comes from a race scenario: 50 km ridden 80% in the upright position at 300 W and 20% in the aero position at 400 W. To estimate the gap on your own rides, compare this scenario with your habits, especially distance, average power and time spent in the aero position.

The Comete Ultimate aero helmet meets the same safety standard as the Comete SL and Aksium road helmets: all three are certified to European standard EN 1078:2012+A1:2012. Its shape was developed within the requirements of helmet safety standards. The Comete Ultimate helmet has Mips Air Node Pro, which redirects rotational forces in a crash, and the Comete SL helmet also has MIPS, which the Aksium helmet does not. Most crashes happen at an angle, and MIPS uses a low-friction layer that reduces the rotational motion of the head in these angled impacts.

The development of the Comete Ultimate aero helmet followed an iterative process: 2D and 3D design, CFD simulations, then wind tunnel testing. The programme included more than 750 hours of CFD simulations, 108 of them for optimisation, and 25 hours of wind tunnel testing. The simulations refine the interaction between the helmet's surfaces and the airflow. Several successive versions of the helmet were then tested in the wind tunnel to validate these results. The AeroFlow disruptors came out of these iterative tests.