Bicycle Safety Program

You can't get the most protection from your helmet unless it fits well. The helmet should be comfortably touching the head all the way around. It should be level on the head and stable enough to resist even violent shakes or hard blows. You want the helmet as low on the head as possible to maximize side coverage, fitting uniformly all the way around, with the strap comfortably snug so that you can still open your mouth but the strap does not pinch, bind or cut into your chin, and the helmet cannot be made to rock back and forth more than an inch or so.

Helmets come in many sizes and shapes: egg-shaped, pointy. elongated, narrow, or wide. Helmet manufacturers have different adaptations to producing a helmet that fits as many heads as possible. You should be prepared for the eventuality that the helmet you are trying to fit may not be compatible with your particular head.

Helmets always have at least one set of fitting foam pads for the inside. Many come with more than one set, and the second or even third set of thicker pads can be used to customize the shape. Adjust the side fit pads by using thinner or thicker pads where there is a space, adding thicker pads on the sides for narrow heads, or thicker pads in the back for shorter heads. You may also move pads, particularly on the "corners" in the front and rear. The objective is to make the helmet fit with pads touching all the way around, without making it so tight that it will be a constant nuisance. The helmet should sit level on the head, with the front just above the eyebrows, or if the rider uses glasses, just above the frame of the glasses so it does not bump on them.
A note on air channels: for maximum coolness you may want to leave gaps in the fitting pads around the head to let air flow in.

You want the chin strap snug against your chin, with the V of the side straps meeting just below your ear with no slack to let the helmet rock back and forth. First, adjust the length of the rear (nape) straps, the length of the front straps, and the location of the V fitting where the straps come together. That may involve sliding the straps through the top of the helmet to get the length even on both sides. Take a few minutes to figure out the strap configuration. Then adjust the length of the chin strap so it is comfortably snug. If it hangs down visibly or you can slide two fingers under it, it is too loose. If it cuts into your chin and is not comfortable, it is too tight.

When you think the straps are about right, shake your head around. Then put your palm under the front edge and push up and back. Can you move the helmet more than and inch or so from level, exposing your bare forehead? Then you need to tighten the strap beside and in front of your ear, and perhaps loosen the rear nape strap behind your ear. Again, the two straps should meet just below your ear. Now reach back and grab the back edge. Pull up. Can you move the helmet more than an inch? If so, tighten the nape strap. When you are done, your helmet should feel solid on your head and comfortable. It should not bump on your glasses when you ride (if it does, tighten the nape strap). You should forget you are wearing it most of the time, just like a seat belt or a pair of shoes. If it impinges on your riding enjoyment, something is wrong. If it still does not fit, keep working with the straps and pads, or try another helmet.