Have you ever had a motorcycle helmet that feels like a sail? Or rather, maybe like a parachute? I have. It's been some time, but I'd be going down the road at some decent clip, find myself turning my head right or left, getting out behind the windshield's safety, and feel like my helmet was trying to lift off my head, taking my chin with it. It was an absolute nightmare for someone as tall as I am.
Most modern helmets nowadays, however, have been aerodynamically sculpted to reduce lift. They've got diveplanes, intakes, and more to reduce the overall lift of the bottom part of the helmet, as its flat surface can, in certain situations, act as a giant freakin' wing. Again, just creeping outside the vortex a windshield makes can be enough to suddenly feel like there's a noose around your neck.
