How to size a motorcycle helmet that actually fits

Most riders buy their helmet a full size too big. It feels comfy in the shop, and three months later it is rattling around at highway speed doing a fraction of the job it was built for.

Here is the truth nobody at the big-box store tells you. A helmet is a single-use safety device that has to be snug to work. Let's get yours right.

Measure your head first

Wrap a soft tape measure around the widest part of your head, about 2 cm above your eyebrows. Measure three times and use the biggest number, in centimetres. Every brand sizes differently, so that number plus the brand chart beats guessing every time.

The cheek-pad test

Do up the strap, then:

• Grab the chin bar and rotate the helmet. Your skin should move with it. If it slides over your skin, it is too big.
• Cheek pads should press firmly, almost like a chipmunk. They break in roughly 15 to 20 percent, so a little tight today is perfect in two weeks.
• Zero pressure points on your forehead after 10 minutes.

If you can slip a finger between your brow and the liner, go down a size.

Shape matters as much as size

Heads are round, intermediate oval, or long oval. The right size in the wrong shape gives you a headache in 20 minutes. Tight at the forehead but loose at the sides means wrong shape, not wrong size.

This is the one piece of gear worth trying on in person. Get fitted at the shop, or browse helmets once you know your size and shape. Spend the ten minutes. Your skull will thank you.