How to Choose a Mountain Bike Helmet

Wether you push or ride up the hills  a good helmet is a critical piece of safety gear.
Article By:
Luke Lydiard
Review Editor
OutdoorGearLab

Last Updated:
Monday

Types of Cycling Helmets


How do you choose a helmet? Just like there are many types of bicycles designed for the many different disciplines of cycling, there are many types of bicycle helmets to cover the needs of different cyclists. There are specific helmet designs for mountain biking, road biking, bike commuting, time trial, and track racing. Just within the genre of mountain biking, there are helmets tailored to cross-country riding, enduro racing, dirt jumping, and downhill riding. Our Mountain Bike Helmet Review includes seven modern, extended-coverage helmets aimed at enduro-style all mountain-riding, and includes a few lids which will meet the needs of weight-conscious cross-country riders. We also reviewed six of the best and most popular full face downhill bike helmets in our Full Face Downhill Helmet Review.

Seven of the helmets we tested. Top to bottom  left to right: Troy Lee A1  Giro Feature  POC Trabec  Giro Xar  Fox Flux  Bell Stoker and Bell Super.
Seven of the helmets we tested. Top to bottom, left to right: Troy Lee A1, Giro Feature, POC Trabec, Giro Xar, Fox Flux, Bell Stoker and Bell Super.

Despite the differences in design, there are some commonalities to cycling helmets. First of all, in order to be sold as a cycling helmet in the US, a helmet must pass the Consumer Product Safety Commission test and carry the CPSC label. The CPSC standard is very different than the Department of Transportation (DOT) standard for motorcycle helmets. Bicycle helmets (even full-face models) do not meet DOT standards and should not be used for motorcycle riding.

Most bicycle helmets are primarily constructed from expanded polystyrene foam. Most modern helmets also have a thin polycarbonate shell which protects the foam and spreads out the force of an impact over more of the polystyrene. Helmets absorb impacts through partial destruction of both the shell and foam layer, and therefore should be replaced after a significant impact. Helmets are typically held in place by a webbing harness which fastens underneath the chin. The harness's ability to hold the helmet in place is very important and also part of the certification standard, along with the helmet's impact absorbing ability.

Cycling helmets can be broken into two categories: Full-face and half-shell. The difference is just like the name implies. Full-face helmets cover the entire head and include a chin guard which covers the front of the face. Half-shell helmets are shaped roughly like half of a sphere and cover primarily the top of the head. There are many types of half-shell helmets aimed at many types of cycling. The two most common are mountain biking and road biking. Full-face helmets are aimed at aggressive downhill mountain biking and bmx riding.

Three distinct types of bicycle helmets. From left to right: Full Face Mountain  Half Shell Mountain and Road Bike.
Three distinct types of bicycle helmets. From left to right: Full Face Mountain, Half Shell Mountain and Road Bike.
Notice the difference in coverage between a Road Bike Helmet (left)  a Half Shell Mountain Bike Helmet (center) and a Full Face Downhill Helmet (right).
Notice the difference in coverage between a Road Bike Helmet (left), a Half Shell Mountain Bike Helmet (center) and a Full Face Downhill Helmet (right).

Half-Shell Mountain Bike Helmets


Mountain bike helmets are designed for off-road riding of all kinds. Half-shell mountain helmets are very similar to road bike helmets. The main thing that sets a mountain lid apart from a road lid is the inclusion of a visor. Visors serve to shield the eyes from from sun, mud, and rain. While both road and off-road riders may benefit from this type of eye protection, road helmets typically do not have a visor because it would impede the vision of a cyclist riding in the typical forward position on a road bike. The riding position on a mountain bike tends to be more upright, so visors don't interfere with the line of sight as much. Helmet visors, which are also found on full-face helmets, are usually adjustable in angle to allow for more or less eye protection. You can think of a helmet visor like a car sun visor which flips down to shield the eyes when you need it, and then up and out of the way when you don't.

The Troy Lee A1 is a half shell mountain bike helmet. This helmet is part of a newer generation of mountain bike helmets which have more rear and side coverage than older designs.
The Troy Lee A1 is a half shell mountain bike helmet. This helmet is part of a newer generation of mountain bike helmets which have more rear and side coverage than older designs.

Helmets designed for mountain biking typically have more coverage, and therefore more protection, than road bike helmets because mountain bikers are more likely to crash as they negotiate uneven terrain. Half-shell helmets are not designed to be worn with Leatt style neck braces. These braces are designed to protect the neck from various injuries only when coupled with a solid full-face helmet. Never wear a neck brace with a half-shell helmet!

Most mountain bikers combine their visored helmets with sunglasses for eye protection, but a growing number of enduro riders are wearing goggles. Goggles provide better protection in dusty or very muddy situations than glasses. Goggles can also be more secure than glasses. We've actually found that they improve the security of some half-shell helmets. The downside to goggles is that they usually aren't ventilated enough to prevent fogging when you are cranking uphill at low speeds. The Bell Super 2R MIPS and Bell Super 2 MIPS both have a visor which articulates upward enough for goggles to be stored on the front of the helmet while you crank uphill.

We think that half-shell mountain bike helmets are the most versatile bicycle helmets. Since the visor can be removed on most helmets, they can be used for road biking and are perfectly fine for commuting or recreational riding. Mountain helmets also tend to be less expensive than road or full-face helmets. If you are new to biking and are going to start out with just one helmet, we recommend you check out some of the less expensive mountain bike helmets like the Bell Stoker or Giro Feature.

Mike Sharrar training for the upcoming enduro racing season in the Flux.
Mike Sharrar training for the upcoming enduro racing season in the Flux.

Full-Face Downhill Mountain Bike Helmets


Full-face bicycle helmets encompass the entire head and have the most coverage of all types of bicycle helmets. They are designed for very aggressive riding where violent crashes are likely. Full-faces have a chin guard which protects your grill from rocks and dirt sandwiches. This style of helmet, aimed at downhill mountain biking and bmx riding, is the least ventilated type of helmet and can feel a bit suffocating for those who are not used to them. Full-face helmets cover the ears, which adds protection but can make them hard to put on and hard to hear out of. Full-face bicycle helmets carry the same CPSC helmet certification as half-shell helmets but are not DOT certified for motorcycle use. See our Full-Face Review for our favorite helmets for lift-assisted riding.

The Bell Transfer 9 is a Full Face Downhill helmet. Downhill helmets are typically worn with goggles and can be combined with a neck brace for very aggressive riding.
The Bell Transfer 9 is a Full Face Downhill helmet. Downhill helmets are typically worn with goggles and can be combined with a neck brace for very aggressive riding.

This type of helmet is typically worn with goggles. Wearing sunglasses with a full-face is considered a fashion faux-pas by most downhill riders.

Since full-faces have so much more coverage than half-shell helmets, full-faces tend to be the heaviest genre of helmets. Many manufacturers make a polycarbonate and a carbon version of their full-face offering. The carbon version is usually slightly lighter but goes for bookoo dollars when compared to the plastic version.

Rather than a Y shaped yoke connecting the helmet to the chin strap, full-face helmets are secured with a single chin strap that is anchored to the helmet somewhere beneath the ears. Theses straps are typically secured with threaded double D rings rather than plastic buckles, and make the helmet a bit harder to put on between runs.

Modern neck braces such as the Leatt DBX 5.5 can be combined with a full-face helmet to increase neck protection in the case of a bad fall. Neck braces are designed to protect the spinal cord by redirecting forces away from the neck and onto the shoulders or torso. Neck braces can also be worn with DOT full-face motorcycle helmets, but they must never be worn with any type of half shell helmet.

Road Bike Helmets


Bicycle helmets designed for road bike use are typically designed with two things in mind: light weight and excellent ventilation. Since road riders tend to crash a bit less than dirt riders, helmets designed for the road sacrifice coverage for added ventilation and lighter weight. This type of helmet typically has the least amount of coverage and does not have a visor because one would interfere with the field of view in the forward position on a road bike. Normally on road helmets, in place of an attached plastic visor, road bikers often combine a non-visored helmet with a short brimmed cycling cap to shield the eyes from sun or rain. Another design priority in road helmets is aerodynamics, which is another reason road helmets forego the visor that would catch too much air while you crank past cars on the downhill.

The Kask Vertigo is an example of helmet designed specifically for road cycling.
The Kask Vertigo is an example of helmet designed specifically for road cycling.

Road bike helmets are typically the lightest available. The lightest models can weigh as little as 8 ounces. For comparison, the average of the half-shell mountain helmets we've tested is 12.7 ounces, and the average full-face helmet in our up-coming review weighs around 40 ounces. Our testers all agree you can feel the difference of a few ounces in a helmet as soon as you put it on. To find the lightest and most comfortable helmets for road riding, check out our Best Road Bike Helmet Review.

Road crashes can be some of the highest speed crashes, yet these helmets have the least coverage and possibly less protection than other styles of helmets. Not to mention the thin layer of spandex protecting the rest of your carcass.

Aero and time trial helmets are also technically also road bike helmets. These very purpose-built helmets are aimed at maximizing aerodynamics and speed during road races, triathlons, and time trials. We haven't tested any of these ridiculous looking lids yet, but we may in the future. Remember that these helmets are designed to be worn only on race day and really are not suitable for everyday use. However, there are more day-to-day aero designs being created, such as the Giro Air Attack Shield, which is a more aerodynamic helmet for everyday road riding.

Certifying Agencies and Certifications


In the United States, the certifying agency for bicycle helmet safety is the Consumer Product Safety Commission. In order for a bicycle helmet to be sold in the US, it must pass the CPSC test and bear the CPSC label. All of the helmets in our test have this label. All of our test helmets also carry the CE EN 1078 label, which is a similar European standard. None of the bicycle helmets we have tried meet the DOT standard, and should not be used for motorized riding of any kind.

If you would like to read a history of bicycle helmet standards in the US check out http://www.helmets.org/standard.htm.

How to Properly Wear a Helmet


If you look around your local bike path, you will likely see many riders improperly wearing their helmets. The tendency for many riders, beginners especially, is to wear a helmet much too far back on the head. If you are familiar with the ski/snowboard term of "gaper gap" then you know what we are talking about. We also see many chin straps that are much too loose to hold the helmet in place during a tumbling crash. We think both of these trends are especially common in children, which makes us cringe.

So how do you properly wear a helmet? For starters make sure the helmet is level on your head from front to back. The sweat band should sit just above the eyebrows, not up where your dad's hairline is. Second, crank the rear adjustment band tight (hopefully you started with it fully loosened) by turning the wheel or sliding the sliders until the helmet feels secure on your head. The third step is to adjust the harness so that the helmet will stay put while you wing through the air before hitting the ground. We've found there is a fine line between a properly tightened chin strap and choking. Helmets which have Y-shaped yokes that allow fore/aft adjustment of the chin strap make this a bit easier. Basically, you want to position the chin strap far enough forward to not crimp your trachea but far enough back that it won't slip off from under you chin. Now put on some eye protection and go shred.

How to Properly Size a Helmet


Getting a correctly sized helmet is imperative to getting a proper fit, which will allow a helmet to protect your dome to its fullest potential. The majority of the mountain helmets in our test come in three sizes, while the Bell Stoker comes in four. Folks with gargantuan noggins should take note, the Bell size chart indicates the XL Stoker will accommodate heads up to 65cm. The size range of the rest of the helmets in our test topped out at either 62 or 63cm.

To figure out your head size we recommend you measure the circumference of your head using a flexible measuring tape. Go completely around your head on a level plane, beginning and ending just above your eyebrows. Don't have a flexible tape? Just use a piece of non-stretchy string and then compare it with a rigid measuring device, like a ruler. You can then compare your number with our handy size chart where we've compiled all of the manufacturers' size recommendations in one place.

A comparison of the size ranges of the half-shell mountain bike helmets covered in our review.
A comparison of the size ranges of the half-shell mountain bike helmets covered in our review.

The bottom line is, just like everything else that's fun, riding a bike is dangerous, and you should wear a helmet every time you get on your bike. No matter what type of helmet you decide to go with, wearing one will be safer than not wearing one at all.

Luke Lydiard
Luke Lydiard
About the Author
Luke Lydiard was born and raised in the hills of Western Massachusetts where he spent most of his days finding ways to ride a snowboard. He quickly moved west seeking larger mountains and deeper snow. In the Eastern Sierra, Luke fell in love with climbing as much as snowboarding. He currently lives and works in Mammoth Lakes, California where he balances a full time job as a Paramedic Firefighter with traveling the world seeking inspiring lines for both ascending and descending. Luke has climbed rock, snow, and ice in France, Canada, Chile, Argentina, and Alaska.

 
 

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