How to Choose the Best Full-Face Helmet for Downhill Mountain Biking

Three distinct types of bicycle helmets. From left to right: Full Face Mountain  Half Shell Mountain and Road Bike.
Article By:
Luke Lydiard
Review Editor

Last Updated:

Bike helmets come in nearly as many styles as there are styles of bikes. You probably already know that you would want a different bike for shredding the bike park than for grinding out a road century. What you may not know is that you should also have different helmets for these two very different genres of cycling. Downhill, enduro, cross-country, dirt jump, road biking, and time trial all have specially designed helmets which vary as much as these types of bikes do. The bottom line is, if you own a quiver of bikes you are also going to want at least a couple of different helmets to optimize protection, weight, comfort, ventilation, and features depending on what type of riding you are doing.

To see all of the factors which make a good helmet, click over to our Best Full-Face Mountain Bike Helmet Review. If you are looking for a helmet aimed more at cross-country, trail, all-mountain, or enduro riding then head over to our Best Mountain Bike Helmet Review.

Types of Bike Helmets

Road Bike Helmets

Kask Vertigo in Azzurro.
Road helmets are typically designed with low weight and maximum ventilation as the main objective rather than protection and durability. Though they are comprised of less raw materials than most mountain bike helmets, road specific helmets tend to retail for considerably more. Since crashing is less common on the road than on the trail, a road helmet may end up lasting a lot longer than the average mountain helmet. Road helmets carry the same certifications as half-shell mountain bike helmets. Reference our Best Road Bike Helmet Review to find the lightest and most comfortable helmets for this style of riding.

Besides being lighter and better ventilated, the lack of a visor is what we feel makes a road helmet a road helmet. While mountain bikers will benefit from the added eye protection from a visor, a visor will interfere with looking down the road when riding in the drops on a road bike. Roadies looking for a shield from rain or sun will typically combine a helmet with a lightweight cotton cycling cap that can be flipped up if it obstructs the view.

Aero helmets are niche products designed for road biking. These funny looking lids are designed to shave seconds off the clock in time trials and triathlons. Recently a few manufacturers have released hybrid aero helmets that are supposed to increase aero efficiency without the massive tear drop shape commonly found on a time trial helmet. An example is the Giro Air Attack Shield.

Half-shell Mountain Bike Helmets

Giro Feature in Bright Green
Half-shell mountain bike helmets, the focus of our Best Mountain Bike Helmet Review, cover around half of the head. These helmets protect the top and some portion of the rear of the head but do not have a chin guard. The latest generation of half-shell mountain helmets, many of which were included in our review, have deeper rear coverage than past helmets ,and are better suited for aggressive riding. Half-shells in general are aimed at a wide range of mountain bike disciplines, from cross-country to enduro. They will also work just fine for commuters or casual cyclists just looking to protect their domes.

Half-shell helmets weigh around one-third the weight of a full-face helmet, have much better ventilation around the head, and don't restrict breathing at all. The downside to half-shells is that they don't offer nearly as much coverage as a full-face. Half-shell helmets should never be combined with neck braces. If you do you'll break your neck for sure.

Half-shell mountain bike helmets and road bike helmets are typically certified to the CPSC and CE EN 1203 standards that are not specific to a certain type of cycling, but are required for a product to be sold as a cycling helmet in the US and Europe. See below for more on certifications.

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).

Downhill Full-Face Helmets

Bell Transfer-9 in Yellow Purple Hydra
Full-face helmets are the most protective type of cycling helmet and are aimed at very aggressive riding where serious crashes are not just possible but are common. The trade-off for the extra protection is greatly increased weight and decreased ventilation. Full-face helmets weigh around three times as much as half-shell mountain bike helmets and are much hotter because the extra coverage traps a lot more air around the head. First time full-face wearers often feel as if they are suffocating in them because the chin guard restricts air movement around the mouth and nose, no matter how well the helmet is designed. Since they also cover the ears, full-faces also restrict hearing, but traffic isn't usually a problem on the mountain bike, so this isn't too big of a deal. Just try to notice when a faster rider catches up to you on A-Line. With a little experience, most riders get used to wearing a full-face and find that the added weight and decreased airflow is worth the added security when riding gnarly terrain.

Full-face helmets protect your entire head by covering the entire occipital lobe, temporal area, ears, and jaw. This type of helmet looks very similar to a motocross helmet with a large open area in front of the eyes, making it ideally worn with goggles.

Full face helmets should be worn with goggles. Don't be this guy.
Full face helmets should be worn with goggles. Don't be this guy.

Also similar to motocross helmets, full-face downhill helmets have large visors designed to shield the eyes from sun, rain, or mud depending on riding conditions. These visors can be manipulated up and down a few degrees for optimum placement. They can also be removed completely, though we feel that they add a bit of style to the helmet and we prefer to leave them attached, even if they aren't helping us see better. Additionally, full-faces are the only type of helmet that should be combined with neck braces. If you don't know what those are, see Neck Braces below.

These types of helmets are certified by the same CPSC and CE EN standards as half-shell mountain and road helmets, and usually also meet additional standards aimed at downhill riding. See our certification section below for more on these standards.

Motorcycle and Dirtbike Helmets

Troy Lee Designs SE3 Moto Helmet
While these helmets look and feel similar to a helmet designed for downhill mountain biking, Moto helmets are certified by the Department of Transportation and can legally be worn on a motorized vehicle on the road. A full-face mountain bike helmet should never be worn on any type of motorized vehicle because it is not rated for as high speed crashes as a helmet that is DOT certified. DOT helmets are being worn by some downhill/bike park riders who feel that they offer superior protection for the types of impacts they are likely to take. We've heard arguments on both sides though we haven't seen any scientific studies which side with either camp.

None of the full-face helmets in our test meet any DOT certifications. Whether or not DOT certified helmets make for more protective bicycle helmets we will leave to the inter-web debaters, though a helmet designed for mountain biking is sure to be more ventilated and comfortable.

Helmet testers pushing up for another lap.
Helmet testers pushing up for another lap.

Other Safety Considerations


All of the helmets in our test meet the CPSC and CE EN1078 standards for bicycle helmets sold in the US and Europe. These two certifications are not specific to full-face helmets. In fact, all of the helmets in our half-shell mountain bike helmet review as well as in our upcoming road bike helmet review also meet both of these standards. The majority of full-faces we tested also meet an additional standard that is specific to full-face bike helmets designed for more aggressive riding and potentially worse crashes. That standard is the ASTM-F1952. We think that downhillers should consider this as the minimum standard to look for in a full-face helmet. Two helmets in our test do not carry the ASTM-F1952 label, and those are the Bell Sanction and POC Cortex Flow.

You can read an interesting history of bicycle helmet standards in the US to learn more on this topic.

Neck Braces

Neck braces, like those made by Leatt or Atlas, are rapidly gaining popularity amongst downhillers. Our favorite is the Leatt DBX 6.5. These braces work by redirecting impact forces away from, and by limiting the motion of, the vulnerable cervical spine. Neck braces are designed to be worn with full-face helmets only, and work because during a crash the helmet makes contact with the table of the brace, preventing your neck from bending. Please remember YOU SHOULD NEVER WEAR A NECK BRACE WITH A HALF-SHELL BIKE HELMET.

While these braces are not perfect, we feel that they have the potential to prevent life changing injuries, and we certainly wouldn't talk anybody out of wearing one for aggressive mountain biking. We have a few testers who never ride in a full-face without also wearing their Leatt.

We found the Bell Transfer-9 to be very compatible with a Leatt DBX as well as Smith Fuel goggles.
We found the Bell Transfer-9 to be very compatible with a Leatt DBX as well as Smith Fuel goggles.

All of the helmets in our test were worn with a Leatt DBX neck brace by a few of our testers to check for compatibility problems. While we wouldn't say that any of the helmets in our test don't work with the Leatt, we found that helmets with the least downward curve of the chin guard allowed for better range of motion while on the bike. One helmet that has a radical downward sloping chin guard is the Bell Sanction, and it doesn't make for the best match with the Leatt. Since the Sanction is likely the least protective helmet in our test, we don't think that many riders will be looking to combine the Sanction with a neck brace for added protection anyways.


Fit is likely the most important single characteristic of a helmet that encases the entire head. Since head shapes vary from rider to rider, there is no way we can quantify fit for you. The best thing to do is to try on as many helmets as you can. A full-face helmet for downhill mountain biking should fit very snugly so that it doesn't rattle around as you bomb through rough sections. Since full faces don't have a tightening mechanism around the back of the head like half-shell helmets, you should strive for a fit that is tight enough to stay put on its own.

Always remember to fasten the chin strap. We've heard more than one horror story of a rider forgetting to fasten the strap and having the helmet pop off in a violent crash. Chin straps should be worn as tight as you can handle without feeling as if you are choking.

Full-faces are sized by measuring the circumference of the head on a level plane just above the eyebrows using a flexible measuring device. Don't have a flexible measuring tape? Just use a non-stretchy piece of string and then compare to a rigid measuring device. We've compiled a chart with all of the manufacturers' sizing recommendations in one place for you to more easily select a size based on your measurement.

A size chart for the full-face helmets in our test.
A size chart for the full-face helmets in our test.

Head Shapes

Back when we tested Ski and Snowboard Helmets we found that head shape really affects the fit of a helmet that fully encases the head. We found that head shapes, when viewed from the top down, come in a range of ovals which we put into three categories: round oval, intermediate oval, and long oval. It's hard to use a tape measure to determine which head shape you have. Instead we recommend trying on as many helmets as you can get your hands on. You can do this at your local bike shop, by grabbing a friend's helmet (hopefully before they've sweated a bunch in it), or by taking advantage of online retailers with liberal return policies that allow you to try things on.

A diagram of the three types of head shape. When fitting a helmet look for brands tailored to your head shape. Giro uses a long oval design for most of their helmets and Smith fits round oval heads best. Troy Lee also tends to fit people with rounder heads.
A diagram of the three types of head shape. When fitting a helmet look for brands tailored to your head shape. Giro uses a long oval design for most of their helmets and Smith fits round oval heads best. Troy Lee also tends to fit people with rounder heads.

Based on our test helmet selection, we found that the Troy Lee D3 has a very round oval shape while the Giro, Bell, POC, and Fox helmets have a more neutral shape.


There's no two ways about it, downhilling is an expensive sport. However, we recommend that you find other parts of your kit to save money on rather than skimping on protective gear. Ambulance rides, CT scans, and dental surgery all cost many times more than any of the helmets we tested.

The helmets in our test varied from a mere $75 to a whopping $375. That's a 500% increase from the least to most expensive. You have to wonder, is the Troy Lee D3 five times better than the Bell Sanction? Maybe not, but consider that a CT scan of your head costs multiple thousands of dollars at any American hospital, and you may want to reconsider how much you spend on safety equipment. Throw down a little extra cash on your helmet before you throw down on the hill and you might not have to throw down at the ER. The bottom line is, we recommend you spend as much as you can on a helmet.

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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