It’s not uncommon among gravity riders to assume that Motocross helmets are always safer than full-face bicycle helmets. While that may seem like it would make sense, with Motocross helmets being larger and heavier and having more ample padding between the head and the helmet than mountain bike helmets what would mean the real difference?

Well, the answer is not exactly straight forward. There is much debate about helmet stiffness and how it influences the level of protection a rider would actually receive in a crash. Critics complain that most motorcycle helmets are engineered to be so rigid that in the end, they can actually intensify an injury in the most common types of crashes. So the choice to substitute a Motocross helmet for a bicycle helmet for downhill rides, the difference could be critical.

Helmet testing at the labs is mandated by the Department of Transportation, and involves the helmets being dropped onto differently shaped objects at different speeds, from a variety of different heights. These tests help the engineers to understand how a motorcyclist’s head would be affected from an accident occurring at highway speeds.

The SNELL Memorial Foundation is a non-profit group that has provided certification for motorcycle helmets for many years, and the testing they use involves more stringent criteria, with more significant pressure and stressors placed upon the helmets during testing than the standardized DOT testing which determines whether or not a helmet will be sold in the US. The most recent SNELL certification standard requires that a helmet transmit under 275 g-forces to the headform inside of the helmet during any phase of testing.

In order to sustain a force of 275 g-forces, motorcycle helmets must be a lot stiffer for such severe impacts, under the SNELL standard. This level of stiffness is not good for mountain bikes.

Safety features on the helmet are implemented to slow the head down during impact. The EPS foam inside of the helmet is what mainly handles this task, as it compresses upon impact, which is what slows the head down. If the foam fails and the head is not slowed sufficiently during impact, the brain will sharply strike the inside of the skull, which, at best, will produce a concussion. If the helmet is even more inferior, the consequences are unimaginable. Motorcycle helmets are designed to withstand the brutal impacts resulting from a street or highway accident, so they have a stiffer helmet liner. The problem is that a helmet designed to withstand highway speed force will be entirely too stiff to offer even an ounce of protection from an impact involving lesser speed, at a smaller distance.