All motorcycle helmets have four common parts:
- A hard shell.
- An energy dampening layer.
- The comfort liner.
- A retention system.
The Hard Shell is the outermost part of the helmet and is your first line of defense against really bad things happening. It’s usually made from thermoplastics or fiber-reinforced composites, such as fiberglass, carbon fiber, or other similar materials. The Hard Shell’s main function is to prevent penetration of the helmet by a pointed object that might otherwise puncture the energy dampening layer (and your skull). It also provides structure to the inner liner, so it doesn’t disintegrate upon impact or abrasion.
Each Hard-Shell material has its own benefits. In general, polycarbonate plastic is used on lower-priced helmets to save costs. Higher end helmets usually have shells made from fiberglass or Kevlar / carbon fiber. These high-end fiber composites do cost more, but they disperse the energy better – which means there’s less energy that the energy dampening layer need to absorb.
The Energy Dampening Layer is the part of the helmet just inside the hard-shell and is designed to absorbs the energy during an impact or crash. It’s most commonly made from polystyrene, a fancy term for Styrofoam.
The thing to remember here is that this layer crushes during impact. That’s why it’s HIGHLY recommended that you get yourself a new helmet if that ever happens to you.
(There are some things that you just can’t re-use.)
The Comfort Liner is the padding and soft foam-and-cloth layer that sits next to your head. It’s there to make the helmet fit nice and snug. Again, it’s there strictly for comfort, as its name implies. (Note that with some helmets, you can take the comfort layer out when cleaning.)
Retention System is a fancy phrase for chin strap. This secures the helmet on your head and while it may not seem as important, trust me it IS. Make sure that EVERY time you put the helmet on, you fasten the strap securely. Just do it. It only takes of couple of seconds.
Riding without your helmet completely secured would be as ridiculous as jumping from a plane without buckling your parachute. You put all this effort into making sure the helmet fit properly – don’t risk injury by not securing it to your head.