6D Alterra Enduro Helmet | Trail Tested

April 11, 2025

Price: $395

Certifications: Meets or exceeds CPSC, EN1078, AU/NZS 2063, 8776 E-Bike standards, as well as ASTM F1952 (Downhill) and ASTM F2032 (BMX)

By Donn Maeda

Several months ago, I was riding mountain bikes with my buddy Tod Sciaqua and we were discussing the fact that we were jumping motocross-sized obstacles and traveling downhill at decent speeds with some pretty unforgiving terrain around us, and that we should probably consider wearing full-face helmets on certain trails and/or on sendy days. While most downhill mountain bike helmets are pretty close to a motocross helmet albeit lighter and a bit smaller, the full face helmets we decided that we should wear are of the “enduro” variety: a full-face helmet with complete coverage on the back of your head, as well as a chin bar to protect your face, but with generous venting built in so that the helmet is tolerable while pedaling/climbing and breathing heavy. Ironically, though we both procured some helmets of said design, both of us ended up having decent crashes in our trusty half-shell helmets. Sadly, Tod’s crash was horrific crash and he was flown out of the mountains on a stretcher suspended from a helicopter, and spent a few days in an induced coma while his brain was recovering from the impact. Much of the impact was absorbed by his face and he suffered a pretty bad contusion. Tod has made a great recovery, but although it has been months now he has yet to return to the level of riding he was previously at. My crash was much less severe, but it did leave me with a black eye that made me look tough… I always joke that crashes that make your sunglasses fly off are big ones, and to be honest I never found them!

Last June when 6D debuted the ATR-3 motocross helmet to the media, they also had a prototype mountain bike helmet on display that was super trick looking. Boasting a two-piece shell that included a carbon fiber chin bar and inner roll cage, the Alterra boasted the highly ventilated design of most full-face enduro helmets, but carried e-bike and downhill certification ratings. Why is there an e-bike rating? Well, in addition to allowing you to reach greater speeds thanks to the electric pedal assist, most e-bikes weigh in over 50 pounds and can do a lot more damage to your skull than a pedal bike if it hits you in the head! Of course, the Alterra boasts 6D’s omni-directional suspension system to protect against rotational brain injuries, as well as an inner EPP liner and outer EPS liner for layered impact protection inside of the polycarbonate outermost shell. Also built in to the helmet are EPP pads on the bottom of the chin bar for collarbone protection in the event of a crash that drives the lower edges of the helmet into your shoulders.

To be honest, I was almost more intrigued by the prototype Alterra than I was the ATR-3 (which is awesome, by the way) CLICK HERE FOR MORE ON THE ATR-3 and I did my best to convince the 6D crew to let me walk away with the one on display. Sadly, there was no such luck, but they did procure a pre-production Alterra for me to test a few months later. That said, I’ve been riding in my Alterra for over five months now and have plenty of opinions to share about it!

First of all, the Alterra is super light and very comfortable. Looks are always in the eye of the beholder, but I think the helmet looks super cool, and especially the black version that I ride in. If there was one design feature I wish it had…I’d make the visor a tiny bit longer so that it balances out with the chin bar a little better. However, I’ve found that no matter whether I’m in a full-face or half-shell helmet, I always tend to have the visor pushed up as high as it can go. As far as the Alterra is concerned, the visor has three “click” positions; the highest of the three allows you to put your goggles on the forehead of the helmet with one hand when the trail points uphill. See below!

The helmet has massive vents everywhere and airflow has never been a problem; in fact during some of the colder winter mornings I felt that it flowed too much air. Notice the vent in the photo above, placed right over your ear. Having airflow to your ears really helps dissipate heat, and I like being able to hear everything from the sound of my knobby tires sliding on the dirt, down to the click of my drivetrain shifting gears.

I already mentioned that the Alterra is comfortable, but I need to mention it again. Everyone has unique head shapes, but for me, the newest 6D MTD helmet has no pressure points, slips on easily without tearing off my ears, and didn’t require any adjustments. Sizing is true and mirrors the 6D motocross helmets: I wear a medium in both. The Alterra comes with some extra fit pads to dial in the fit, but mine was perfect as delivered. The chin strap his a magnetic Fidloc closure that is easy to open and close with one hand.

Remarkably, I made it through the past five months without smashing my Alterra into the earth, and managed to keep it off my social media and off the radar of riders outside my group of friends before it was released to the public. As luck would have it, a couple of days before 6D debuted the Alterra and made it available to the public, I lost my front end on a tricky rock roll, slid down a massive granite slab on my stomach, head first, and bonked by head on the sizable helper rock laid at the bottom to make the transition to dirt a smoother affair. The visor ejected on impact and the forehead of the helmet took the brunt of the impact, and believe it or not: I felt the helmet’s omni-directional suspension system do its job as the helmet rotated downward and protected by neck from the impact. After I mourned the holes ground into the thighs of my new Volcom MTB pants and stomach of the matching windbreaker, I snapped the visor back onto my Alterra and rode two more laps on my favorite trails.

At $395, the 6D Alterra is not cheap, but when it comes to protecting your brain (and face), it’s a small price to pay for peace of mind and confidence in what you’re strapping onto your head. And have you been to the emergency room lately? Even with good insurance, co-pays can be brutal!

Available in six colors and three sizes, the Alterra is available now but in the week since its unveiling, several options are already sold out. Move quick if you want one of these babies! And tell ’em SML sent ya!

CLICK HERE