Most riders will be familiar with the extreme aerodynamic helmets favoured by time trial riders; usually teardrop shaped and free from vents. The lack of vents may improve air flow over the helmet but it does nothing for comfort.
However, the subject of aerodynamics in relation to helmets is starting to make its presence felt in designs for road racing and committed club cyclists.
The main feature of aero road helmets that have started to appear on the market in recent years is a lack of vents; not the complete lack seen in TT helmets but enough to direct airflow over the helmet rather than through it.
These aero road helmets first came to prominence when Team Sky were seen wearing Kask’s Infinity helmet, but things have evolved since then and the focus for manufacturers now is to produce a helmet which gives the rider an aerodynamic advantage without sacrificing ventilation. Current design that seek to tick both boxes include the Kask Protone (review), which has large vents at the front and rear, and a smooth top section, as well as the Giro Synthe (review), Specialized Evade and Bell Star. The R&D time put into developing these helmets, as well as the advanced manufacturing techniques, means they’re not cheap.
For those that want a helmet that can function as a regular or aero design then there are choices such as Lazer’s Z1, which has an optional aero shell to cover the vents and provide increased aerodynamics, or left off for increased cooling airflow.