What helmets are they racing in ?
The lightest full-face motorcycle helmet you can buy right now, the Nexx XR1R Carbon.
The XR1R is the product of a tiny, specialist helmet manufacturer in Portugal. It's ok if you've never heard of Nexx, they've only been making helmets for a few years and they've only just begun to penetrate the North American market.
Why would top sledders choose the helmet? Well, in one word: weight. Weight matters just as much on a bobsled as it does on a motorcycle, which is also why BMW's North America Design Studio creates the sleds.
Because your head sits at the extreme end of your body, any movement or forces your body experiences are magnified by the time they reach your noggin. A few G-Forces are no big deal for your torso, but they are enough to bend your head over onto your shoulders. Rapid acceleration or deceleration, and your head can be thrown backwards or forwards. Any gram you can save on a helmet reduces those effects.
It achieves that through an all-carbon shell and a drastic parts reduction– for instance, there's no quick-change visor mechanism.
The helmet has other advantages, of course. Its horizon line — the level at which your vision is cut off while peering upwards in a tuck — is exceptionally high.