Adults and children who ride bicycles should always wear a helmet. Many states require they do so.
But even without the threat of a legal penalty, it makes sense to wear a helmet when riding a bike. Wearing a properly fitting bicycle helmet reduces the risk of serious head injuries by 85 percent, according to the American Academy of Orthopaedic Surgeons.
Some parents decide to save money by buying helmets that are too large for their child. This is the same money-saving strategy that parents employ when they buy pants or jackets in large sizes, expecting the child to grow into them. But using that same strategy with bicycle helmets is a dangerous gamble.
Whether on an adult or a child, a helmet that has been approved by the U.S. Consumer Product Safety Commission and fits correctly will cushion the head in a fall and protect it from impact with other objects. Riders whose bicycle helmets don't fit right are at twice the risk for serious head injuries, compared with those whose helmets fit properly.
The following guidelines can help you fit a bike helmet correctly.
The right fit
Look for these elements in a helmet:
It should comfortably touch your head all the way around.
It should be level on your head.
It should extend as low as possible to help cover the sides of your head.
It should be stable enough to resist violent shakes or hard blows and stay in place.
It shouldn't rock back and forth more than an inch or so. (If you can tilt a helmet while someone is wearing it, then something's wrong.)
It should protect your forehead. The helmet should be only one to two finger widths above your eyebrows or eyeglass frames.
Adjust the straps
The strap should be comfortably snug so that you can open your mouth, but the strap should not pinch, bind or cut into your chin. A properly adjusted chinstrap fits snugly against your chin, with the V of the side straps meeting just below your ear and no slack to let the helmet rock back and forth.
For a proper fit, adjust the length of the rear 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. Then adjust the length of the chinstrap so it's comfortably snug. It's too loose if it hangs down or if you can slide two fingers under it.
Shake your head when you believe the straps are adjusted right. Then put your palm under the front edge of the helmet and push up and back. If you can move the helmet more than an inch or so, you need to tighten the strap beside and in front of your ear, and perhaps loosen the rear strap behind your ear.
Again, the two straps should meet just below your ear. Now reach back and grab the back edge of the helmet and pull up. If you can move the helmet more than one inch, tighten the rear strap.
When you're done, your helmet should feel solid on your head and comfortable.
As a final note, if you’ve been in a fall with the helmet on and the helmet hit the ground or an object, you should replace the helmet even though there may be no apparent damage.