How to Adjust a Bike Helmet

	These pictures show how a helmet should fit. It should be snug, level and low. The slider should be just below the ear, perhaps slightly in front of it.
	These two pictures show improperly-fitted helmets. The left one is tilted too far back, the right one too far forwards. The tilt is caused by incorrect strap lengths, as shown.

Here are the steps to getting a helmet to fit properly:

1. Make sure that the basic shell is the correct size. Fine-tuning on basic helmets is done by selecting foam pads of proper thickness to go inside the shell, while fancier helmets have an adjustable plastic cage on the back of the head. In either case, make sure that the helmet is large enough to go low on the head, but not so large that it cannot be made snug. There should be two fingers width (child’s fingers) between the eyebrows and the helmet on the forehead, and the helmet should be down near the ear. The helmet should be snug enough that rocking the helmet up and down (after the straps are adjusted and tightened) should cause the forehead skin to wiggle also.
    

2. Adjust the forwards/backwards tilt until the helmet is level. The slider that joins front strap to the rear strap should be just below the ear, with the straps forming a Y (not under the chin, with the straps forming a V). If the helmet is tilted too far back, shorten the front strap and lengthen the rear strap. If the helmet is tilted too far forwards, pull it back by tightening the rear strap and lengthening the front one. The best helmets have sliders which lock in place to preserve proper adjustment. Before changing strap lengths the sliders must be unlocked by flipping up a cap or by rotating a small dial, depending on the brand. The less expensive helmets don't have locking sliders and will not stay adjusted. You can wrap electrical tape around the straps above and below the sliders to make them stay in place.
    

3. Adjust the tightness of the chin strap. It should be tight enough that you can just slip a couple of fingers between the strap and the neck. BE VERY CAREFUL NOT TO PINCH A CHILD'S SKIN when closing the buckle. This is very painful, and it can give young kids an aversion to helmets.

All bike helmets sold in California are required to meet the standards of the Consumer Products Safety Commission. This does not mean that all helmets will protect you equally well. A helmet must be snug and in the proper position when your head hits the ground if you are to get maximum protection. A helmet with locking sliders that will stay adjusted will be more likely to protect you than one that is always going out of adjustment. Styling can be a big issue for kids. Any helmet that they are willing to wear is better than a helmet that they take off as soon as they are out of sight. Buy whatever helmet the child will wear, and deal with any deficiencies (e.g. tape the sliders in place). Parents need to set a good example and wear a helmet if they expect their children to think it is important.

Here is a printable pdf version of the instructions above.

Here is a flyer from the California Dept of Health Services about helmet fit. (3.5 Megabyte pdf)

Here is a Spanish version of the DHS flyer (2.4 MByte pdf)

The National Highway Transportation Association has a pretty good set of instructions, with drawings and a printable version.

Some people think that wearing a helmet isn't cool.

For lots more information on bike helmets, visit the Bicycle Helmet Safety Institute.