The world's most in-depth and scientific reviews of outdoor gear

How to Choose a Mountain Bike Helmet

The Tectal Race is a fantastic helmet with great coverage  comfort  performance  and features.
Tuesday July 31, 2018

Types of Cycling Helmets


Looking for a mountain bike helmet, but not sure which is right for the type of riding you do? In the same way that there are different bikes designed for specific disciplines of cycling, there are a variety of helmets to meet the needs of the cyclists who wear them.

Helmets are made to meet the demands of each genre of cycling, from mountain biking, road biking, bmx, bike commuting, time trialing, you name it. Within the sport of mountain biking alone, there are helmets designed for enduro, all-mountain, cross country, dirt jumping, and downhill. The type of helmet you need will depend on the type of riding you do, in some cases you may even need or want to have several different helmets for your road, trail, or downhill riding needs.

Half-shell mountain bike helmets are the best option for most mountain bikers. These versatile helmets are lightweight  have good coverage  ventilation  and useful features.
Half-shell mountain bike helmets are the best option for most mountain bikers. These versatile helmets are lightweight, have good coverage, ventilation, and useful features.

First, consider the type of riding you do. Do you spend your days pounding pavement on a road bike? Check out our road bike helmets review. Are you an adrenaline-fueled gravity mountain biker who spends the majority of your time riding chairlifts or shuttling laps to bomb the downhills? Then you should check out our Full Face Downhill Helmet Review.

Are you more of an all-around rider who is looking for a comfortable and protective lid that can do it all? Then you'll probably want to check out our Mountain Bike Helmet Review aimed at enduro-style all mountain-riding and includes a few lids which will meet the needs of weight-conscious cross-country riders.

Half-shell mountain bike helmets are designed to meet the demands of trail riders  with more coverage than road bike helmets  and visors to shield your eyes from the sun.
Half-shell mountain bike helmets are designed to meet the demands of trail riders, with more coverage than road bike helmets, and visors to shield your eyes from the sun.

Mountain Bike Helmets


You can divide mountain biking helmets into two basic categories — full-face and half-shell. The differences are exactly what the names imply. Full-face helmet models provide full coverage of the head, including a chin and face guard which wraps around the front of the helmet for additional protection. Half-shell helmets offer less protection and coverage than full-face models, covering the top of the head, down on the sides above the ears, and the back of the head.

Cross-country, trail, all-mountain, and some enduro riders will generally wear half-shell mountain bike helmets, while more aggressive downhill, enduro, and bmx riders will typically opt for a full-face model. Of course, you can wear any mountain bike helmet for any type of mountain biking. Some are just better suited to certain disciplines than others. This article focuses primarily on half-shell mountain bike helmets, but we will touch briefly on the other types of cycling helmets for comparison.

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.

Half-Shell Mountain Bike Helmets


Half-shell mountain bike helmets are appropriate for the vast majority of mountain bike riders. It's one of the most versatile styles of helmets and works for road biking, commuting, lapping the pump track, and trail riding. Half-shell mountain bike helmets are similar in many ways to road bike helmets, although modern models typically have a visor and more coverage than their road-oriented counterparts. The best half-shell helmets have extended coverage, quality adjustments, a rotational impact protection system, and an adjustable visor. We evaluate the helmets in our review based on several criteria, including protection, comfort, adjustments, ventilation, weight, and features.

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).

Protection


Helmets are designed to protect your head, that is their most important function. In general, helmets designed for mountain biking have more coverage and offer more in the way of head protection, than a road bike helmet. In recent years, the coverage of half-shell mountain bike helmets has been increasing with shells that extend lower on the sides and the back of the head, covering more of the temporal and occipital lobes. A great example of this is the POC Tectal Race SPIN which has a deeper fit than most other helmets and a shell that comes down lower on the temples and the back of the head than the competition.

More coverage = better protection. It's simple science  but it's still science.
More coverage = better protection. It's simple science, but it's still science.

Rotational impact protection systems have also been growing in popularity in all types of mountain bike helmets. MIPS (Multi-directional Impact Protection System) was the first on the scene, and this system features a slip-plane liner integrated into the helmet design between the foam and the pads of the helmet. The idea behind it is that the MIPS liner shifts in the event of an impact to reduce the rotational forces on the brain. MIPS is currently the most common type of rotational impact protection system, although both POC and Leatt have developed their own systems.

POC created SPIN, which is integrated into the pads of their helmet and is claimed to provide a similar slip-plane and also absorb impact at the same time. Leatt's 360 Turbine technology features a number of small "turbines" attached to the inner shell of the helmet and the idea is similar to that of SPIN where it both deflects and absorbs impact.

The yellow MIPS (left) in the Troy Lee A1 and the blue SPIN in the POC Tectal Race SPIN. The MIPS is a shinny plastic surface. POC bakes the SPIN tech into the blue pads.
The yellow MIPS (left) in the Troy Lee A1 and the blue SPIN in the POC Tectal Race SPIN. The MIPS is a shinny plastic surface. POC bakes the SPIN tech into the blue pads.

Proper Fit


For a mountain bike helmet to function properly, you have to get the right size. Mountain bike helmets come in several sizes measured in centimeters. To figure out your head size, 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. In general, each helmet size is intended to fit a range of head sizes. For example, a size medium Smith helmet fits 55-59cm head sizes. Make sure your head measurement falls within the size range of the helmet you order.

The fit of a helmet is also dictated by its adjustments. Adjustable features like the straps and the fit adjustment on the back of the head allow the user to dial in the fit to their exact preferences. Straps are typically adjustable under the chin and also where they split below the ears. Adjusting the straps allows the user to set them up perfectly for their head shape and size and to achieve proper tension so that the helmet stays on your head in the event of a crash. Most modern helmets also have a size or fit adjustment on the back of the helmet to tighten or loosen the fit within a specific range. Since the helmet shell doesn't have a perfect fit for each person's head, the fit adjustment allows the user to dial in the appropriate snugness for their cranium. These days, the fit adjustment is usually in the form of a dial that pulls tension evenly from both sides and cradles the head at the bottom of the occipital lobe.

The Vaporfit dial on the Smith Session is easy to use even with gloves on.
The Vaporfit dial on the Smith Session is easy to use even with gloves on.

In addition to proper fit, a helmet must also be worn properly to function as intended. This means the helmet is level on your head from front to back and the front pads/sweatband should sit just above the eyebrows around the middle of the forehead. The rear fit adjustment should be tightened so that it is snug (hopefully you started with it fully loosened) by turning the wheel or sliding the sliders until the helmet feels secure on your head. You also must adjust the strap harness so that the helmet will stay put on your head even in the event of an impact. We've found there is a fine line between a properly tightened chin strap and one that is uncomfortable.

Weight


In cycling, even mountain biking, everything is subject to weight scrutiny, and helmets are no exception. The differences in weight between half-shell helmets isn't that extreme, but all other things being equal, lighter is better. The half-shell mountain bike helmets we tested weigh between 12 and 14 ounces. Cross-country racers or especially weight conscious riders may be more inclined to find a super lightweight helmet, and sometimes they will trade coverage for weight savings and opt for a road bike style helmet or XC race specific model.

Not the lightest helmet around  but the Session is far from heavy.
Not the lightest helmet around, but the Session is far from heavy.

Ventilation


Half-shell helmets are all designed with some ventilation. The vents of a mountain bike helmet are typically in the form of large holes through the outer shell and foam liner that allow air to flow directly to the head. Many helmets also incorporate air channels that allow the air to flow over the head from front to back to further enhance the ventilating properties of the helmet.

Not all ventilation systems are created equal, and some helmets keep your head much cooler than others. Interestingly, we've found that a helmet's ventilation is not directly related to the number of vents that it has, instead the effectiveness is more related to the placement of the vents and overall design of the system. If you live and ride in an especially hot area, you'll probably be happier and more comfortable with a helmet that has better ventilation, whereas if you live in a cooler climate then ventilation may be less of a concern.

The Tectal Race SPIN's 16 vents do a great job of keeping the air flowing and your head cool.
The Tectal Race SPIN's 16 vents do a great job of keeping the air flowing and your head cool.

Features


Half-shell helmets are being designed with more features to enhance your riding experience or improve their protection. Examples of these features are adjustable visors, rotational impact protection systems, goggle clips, ventilation, GoPro and light mounts, and ways to hold your sunglasses when not in use. Features are great, but only as long as they are actually functional and useful while out on the trail. Overall, we believe that a rotational impact protection system is a great feature to have that may enhance your protection. The price of these systems has come down over the years and nowadays it only costs a little bit more to get a helmet with MIPS or a similar system, we feel it is worth the extra money.


Visors are a feature on virtually all mountain bike helmets. Visors are designed primarily to block the sun from your eyes, although many are adjustable for goggle compatibility. If you like to ride with goggles, you'll want to be sure to get a helmet with an adjustable visor that flips up and out of the way far enough so that you can rest your goggles on the front of the helmet when not in use. If you never ride with goggles, then a fixed visor may work just fine for you.

The features offered by each helmet varies from model to model, and each helmet's features are described in greater detail in their individual reviews.

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.

Full-Face Downhill Mountain Bike Helmets


Full-face bicycle helmets are appropriate for downhill, bmx, and aggressive enduro riding. They encompass the entire head and have the most coverage of all types of bicycle helmets. They are designed for very aggressive riding and higher speeds where violent crashes are more likely. In addition to full head coverage, full face helmets also feature a chin guard which protects your face in the event of a crash. Full face helmet models are generally worn with goggles and are typically much heavier and far less ventilated. But they offer significantly more protection than their half-shell counterparts. If you're in the market for a full-face helmet, then check out our Full-Face Mountain Bike Helmet Review.

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


Bicycle helmets designed for road bike use are typically designed with two things in mind — low weight and excellent ventilation. Since road riders tend to crash a 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. If you're looking for a dedicated road cycling helmet, we urge you to check out our road bike helmet review to find the model that best suits your needs.

Certifying Agencies and Certifications


In the United States, the certifying agency for bicycle helmet safety is the Consumer Product Safety Commission. 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 shouldn't be used for the motorized riding of any kind.

If you want to dive really deep, read a history of bicycle helmet standards in the US.

Conclusion


The bottom line is, just like everything else that's fun, riding a bike can be dangerous, and a helmet is the most important piece of protective gear you can wear. No matter what helmet you decide to go with, wearing one is always a good idea.


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