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 & Patrick Donahue

Last Updated:
Thursday
April 19, 2018
Mountain bike helmets come in all shapes and styles. Riding fire roads and cross country trails call for a very different helmet than charging downhill at a bike park. Downhill and freeride mountain biking feature high speeds, big jumps, and tons of rock. A full-face helmet is critical for downhill and bike park riding. To hear about the metrics and testing process we used to determine the best DH helmets, check out our Best Full-Face Mountain Bike Helmet Review. If you are looking for a daily, half-shell, trail helmet, head on over to the Best Mountain Bike Helmet Review.

Road Bike Helmets


Kask Vertigo in Azzurro.
Road bike helmets are lighter and simpler than mountain bike helmets. These lids typically emphasize ventilation and breathability rather than coverage area. Despite being simpler and using less material, these helmets can be extremely spendy. Shaving grams isn't cheap. You are far less likely to crash on your road bike compared to a mountain bike. As a result, a road helmet should last longer. Still, sweating into a road helmet for years can eventually compromise its integrity.

In addition to a reduced weight and coverage area, the lack of a visor is another distinct characteristic of a roadie helmet. Mountain bikers need visors to help deflect errant branches and for sun protection. On a road bike, the presence of a visor can interfere with your line of sight when you're in the drop position. Roadies looking for protection from the sun and/pr rain will often wear a cycling cap under their helmet.

Check out our Best Road Bike Helmet Review to read about our favorite road helmets.

When thinking about road bike helmets, some might think of aero helmets. While they aren't particularly stylish, these niche products do serve a purpose for some high-level racers. For these racers, seconds matter and reduced wind resistance can be critical. Some brands have hybrid aero helmets that work to make you more aerodynamic without having a full-on teardrop helmet. One popular example is the Giro Air Attack Shield.

Half-Shell Mountain Bike Helmets


Giro Feature in Bright Green
Half-shell or trail mountain bike helmets are far and above the most common lid. They are the clear focus of our Best Mountain Bike Helmet Review. These trail helmets offer additional coverage compared to road helmets. Trail riding has progressed a lot in the past several years. As a result, the helmets have evolved too. It is common to see some extended coverage on the back of the head and near the temples. Some half-shell helmets now have removable chin bars that can be attached at the top of a gnarly downhill for some added safety.

Half-shell helmets are quite a diverse category in and of themselves. Some lean towards the lighter duty cross-country side of things, while others are burly and aggressive looking. Half-shell helmets are typically about 33% lighter than full-face helmets. They breathe well and help keep you cool on hot days. Just keep in mind that sometimes full-face helmets are warranted if you are riding super rowdy or fast trails. These trail helmets are usually certified by 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.

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 offer the highest level of protection. These helmets are highly recommended for bike park and downhill riding. For park and downhill riding, there is a complete and total emphasis on going down the hill rather than climbing. As a result, there is far less emphasis on breathability and weight.

First-time full face users might feel they are too hot and it is difficult to breathe. This comes with the territory but it is also impossible to avoid given the extra coverage. Fear not, riders get used to them fairly quickly and the added protection is totally worth it. Full-face helmets protect your entire head by covering the whole occipital lobe, temporal area, ears, and jaw. Many folks will confuse a full-face mountain bike helmet with a motocross helmet. While they certainly share looks, they are different in size and the safety certifications.

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 entirely, 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 a 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 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



Certifications


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. 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 models 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


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? 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 select a size based on your measurement more easily.

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 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 round, oval shape while the Giro, Bell, POC, and Fox helmets have a more neutral shape.

Price


There are no two ways around 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.