How do bike helmets work?
Cycling helmets typically have a thin shell on the outside, thick foam inside and straps to help keep the helmet in place during normal use and in the event of a crash.
The foam inside is designed to crush and crack on impact, cushioning the blow and dispersing the force of the impact. The shell is designed to keep the foam together in the event of an impact. Some helmets also have a structural cage inside the foam to help the foam keep its shape. And the straps keep the helmet on your head, so it’s important that they’re adjusted properly.
What size helmet do I need?
Choosing the correct helmet size, and then adjusting it so it fits properly is important to proper helmet function. Helmet manufacturers offer several size options and different types of fit systems to help you find your perfect fit. We've included the Bontrager helmet sizing chart below as an example. If you are unsure if you have the right fit, visit your closest Trek retailer or local bike shop for assistance.
Learn more about helmet fit and sizing
| Headform shape | Helmet size | Fit range (cm) | 46 | 47 | 48 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 | 57 | 58 | 59 | 60 | 61 | 62 | 63 | 64 | 65 | 66 |
| STANDARD | Toddler | 46-50 | Toddler | ||||||||||||||||||||
| Child | 48-52 | Child | |||||||||||||||||||||
| Youth/XS | 50-55 | Youth/XS | |||||||||||||||||||||
| Small | 51-57 | Small | |||||||||||||||||||||
| S/M | 51-58 | S/M | |||||||||||||||||||||
| Medium | 54-60 | Medium | |||||||||||||||||||||
| M/L | 55-61 | M/L | |||||||||||||||||||||
| Large | 58-63 | Large | |||||||||||||||||||||
| X-Large | 60-66 | X-Large | |||||||||||||||||||||
| ASIA | S/M | 51-58 | S/M | ||||||||||||||||||||
| M/L | 55-61 | M/L | |||||||||||||||||||||
Bike helmet technology
Most helmets are made with EPS foam, but some are designed with both EPS and additional technologies that are designed to help mitigate certain head injuries. Two newer technologies used in Bontrager bike helmets are Mips and WaveCel.
What’s the best bike helmet for me?
In order to choose the bike helmet that's perfect for you, first consider your riding style and the terrain where you'll spend most of your time riding.
Do bike helmets expire?
Bike helmets have a limited lifespan in use and should be replaced when they show obvious signs of wear. Additionally, helmet parts lose strength over time, so even if the helmet has not been impacted or damaged, we recommend replacing it after three years.
What should I do if I crash?
Bike helmets are designed to absorb shock by partial destruction of the shell and liner. This damage may not be visible. Therefore, if subjected to an impact, the helmet should be destroyed and replaced even if it appears undamaged.
Bontrager crash replacement warrantyCan I replace or remove the bike helmet visor?
Yes, replacement visors are easy to install and are readily available from most manufacturers. It’s also easy to remove your bike helmet visor completely if you prefer to ride without one. Some helmets even come with plugs to insert into the helmet where the visor was taken off to make it more aesthetically pleasing.
Learn more about helmet accessoriesCan I replace or clean bike helmet pads?
Yes, most bike helmet pads are removable and can be easily washed by hand. It’s also easy to find replacement pads for most helmets. If you’re unsure if your pads can be washed, consult your helmet’s manual for your manufacturer’s recommendation.
Learn how to clean your bike helmetCan I adjust the fit of my helmet?
Most helmets are easily adjustable to make the helmet more comfortable to your unique head shape. Fit systems at the rear of the helmet and straps on the sides make it easy to keep the helmet snug and in place.
Learn more about helmet fit and sizingAre bike helmets required?
Every country has its own helmet laws, and in the US, there is no federal law requiring the use of bicycle helmets. Regional laws on bicycle helmet use may vary, so consult the local rules and regulations for where you live and ride. If you are unsure where to find this information, your local bike shop is a great resource.