Aero helmets are heavier, have less ventilation and look much odder than regular cycling helmets. The increased weight and their infrequent appearance at local races might lead you to wonder if the higher price is truly worth it, especially if you’ve already plunked down lots of cash on aerodynamic wheels, aero bars and other bike components. However, top bicyclists choose these helmets for a reason: they do help you cut wind resistance and gain speed.
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Helmet vs. Bike
Wearing a non-aero helmet causes four times as much drag as using non-areo cycling wheels. That’s because your bike accounts for only 15 percent to 25 percent of the overall drag you experience. Your body and the way it interacts with the air accounts for the rest, according to Mark Harrison’s Bicycling magazine article titled “Revenge of the Nerds.”
Aero vs. Standard Helmet
Non-areo helmets commonly worn in cycle races are lightweight but don’t help with drag. In fact, their air resistance is often 110 to 180 g higher than an aero helmet. If you look at it another way, a standard helmet slows you by about one second per mile in comparison to an aero helmet. You can find non-aero helmets that weigh as little as 196 g compared to weights in the 400 g range for aero helmets.
Aero vs. No Helmet
If you wear an aero helmet, you will have less drag than if you're not wearing any helmet. That’s because even if you have short hair, it creates drag. The aero helmet lowers drag by 100 g at 30 mph when compared to riding without a helmet, according to "High Tech Cycling” by Ed Burke.
If you don't employ the correct head position, you won’t get the benefit from your aero helmet. If your head is tipped too high or too low, drag will increase. The head position that’s most often best for aero helmets is one in which your upper back and the bottom of the helmet are parallel, Burke says. With an average aero helmet, your reduction in drag changes from 7.2 percent at a 0 degree yaw angle to a 4.5 percent reduction at a 15 degree yaw angle if you are an elite athlete. If you are average, this difference goes from 5.8 percent to 3.6 percent. You get less drag reduction because you don’t have as much power and speed when you cycle. However, not all aero helmets perform the same at varying angles. You need to consider your speed, preferred head angle and the prevailing wind on your race course when selecting a helmet, according to “The Engineering of Sport 7, Volume 1,” by Margaret Estivalet and Pierre Brisson. For example, if there are lots of cross winds or if you are a slow rider, you need a helmet that performs well at high yaw angles.