Words by Matt Beer
6D is best known in mountain biking for their downhill full-face helmets. Until now, they’ve had a gap between those moto-inspired helmets and an open-face trail lid, the ATB-2T.
This new Alterra helmet from 6D is big on safety and venting, but low on weight. Although it looks like an enduro full-face helmet with a removable chin-bar, it is fixed in place. The chin strap incorporates a Fidlock buckle and the adjustable visor stows goggles for on-trail conveniences.
The carbon chin-bar, along with all of the other tech built into this helmet, shows how 6D prioritizes safety on all fronts. If you’re familiar with 6D’s patent Omni-Directional Suspension (ODS) system, which is used throughout their helmet line, then you won't’t be surprised to find it in the Alterra too.
The recess and padding on the lower edge aims to save clavicles.
From the back, the helmet has a bit of sloping, wide Porsche coupe appearance to it.
This helmet is burly and not the slimmest enduro full-face, despite being fairly light. That means the Alterra helmet exceeds the CPSC/EN1078/AU/NZS 2063 safety standards. Plus, it meets the NTA 8776 E-Bike standard, ASTM F1952 (DH), and ASTM 2023 (BMX) standards. It's currently the top-ranked full face helmet in Virginia Tech's ranking list, although the list of competitors who have also submitted full face helmets for testing is still fairly small. That said, it's still in the eighth spot even when half shell helmets are added into the mix.
The ODS is an attractive safety feature. It is said to function differently than any MIPS slip-plane, including the Split Integra system found in the Fox Proframe RS.
Two foam layers (EPP and EPS) make up the inside of the Alterra. Those are said to handle impacts of varying forces and are connected via the ODS. Those pieces work as a suspension of sorts to absorb both linear and angular accelerations.
On top of that, there’s the multi-impact EPP liner on the inner cup of the shell, and the EPS outside of that. Those two foams are protected by a polycarbonate shell. Up front, an in-molded carbon fiber chin bar adds peace of mind.
The Alterra hides one more safety feature; sternum and clavicle crash pads. These are made from a softer EPP foam in hopes of not causing damage to your bones.
Fit
The Alterra comes in three main shells to span a typical range of heads 53-62 cm in circumference. The XS/S covers 53 to 56 cm, while the M/L from 56 to 59 cm, and the XL/XXL fits 59 to 62 cm.
Included with each helmet are three sets of cheek pads, where the medium thickness is installed, but only two head liners and two neck rolls. All of those pads are made from the popular Ionic+ antibacterial fabric. There are also two strips that cover the chin strap as well.
I found the stock pad set on the M/L to fit comfortably without squishing my face. Instead, they sit further forward and hold the helmet in place well. Some other lightweight full-faces I’ve tried have gotten this place wrong by placing them on the jaw bone hinge, which can be tiring and even painful after a long day.
In terms of shape, the volume inside the Alterra is larger than a Fox Proframe RS, especially towards the top/rear of the head. In some way this is a good attribute because the helmet feels snug and further down over your head.
Along the temple area, the Alterra even has a relief for sunglasses if you’re averse to goggles.
The recess and padding on the lower edge aims to save clavicles.
There's no debating the convenience of a Fidlock helmet buckle.
The M/L is without a doubt the correct shell size for me. It’s snug in terms of circumference, but without an occipital retainer, a third and larger volume neck roll included, the fit could be dialled in further for more stability.
Up top, the visor can be set to three positions with the middle looking the most balanced. The highest position allows goggles to sit on the brow of the helmet. From there, the goggles never snapped down on my face while climbing or traversing and the strap didn’t slide out of place on the shell.
Metal D-rings offer extra security and could be warranted for downhill race speeds, but for enduro riding, the Fidlock buckle closure makes total sense. It’s strong and foolproof. The tension never backed off, which annoyingly, can’t be said for all plastic buckles.
One small improvement 6D could make in this area is on the padding around the plastic buckle. When pulled tight, the padding can slip out of the way, leaving the buckle pressing around the jaw bone. It’s not the end of the world and revising the locations of the loops could be a running change.
Lightweight full-face helmets all seem to have plenty of cut-outs, but there’s something special about the way the air flows into the Alterra, particularly around the forehead and temples. In fact, I’d argue that it’s better than some half-shell helmets. While the daily temperatures haven’t been setting summertime record highs, it has peaked above 20 degrees C a few times.
I also noticed that placing the goggles below the visor, or reversing them, didn’t cause them to fog either.
Historically, 6D helmets haven’t been cheap and the Alterra doesn’t break that mold either. At $395 USD, it’s more expensive than the Fox Proframe RS and POC Otocon by $40, and the Troy Lee Stage by $80.
At that price, you also receive a helmet carry sock and those additional pad kits mentioned. Additionally, the Alterra does come with a 3-year limited warranty on manufacturing defects too.
For what it’s worth, the Alterra comes in six colorways as well; Gloss Black/White, Matte Military Green, Matte Slate Blue, Matte White/Green, Matte Black, and Matte Sand.
Showing off that carbon weave.
The brow vents bring in a substantial amount of fresh air.
6D helmets haven’t always been the lightest, but the Alterra is very respectable at 719 grams. Considering the safety security offered by the ODS system, they’ve done well to drop the weight below a top competitor, the Fox Proframe RS (820 g).
The Troy Lee Designs Stage is still 35 grams lighter and the Specialized Gambit is in another league at just 620 grams.
The visor is small and narrow in comparison to the rest of the helmet volume.
The visor smoothly snaps up a notch or two to stow goggles.
"6D has sparked my interest in lightweight full-face helmets with the Alterra. Its Omni-Directional Suspension system jockeys for top spot amongst other multi-directional and variable force impact designs. Plus, the weight and price are very competitive in that field. Some experimentation with pad kits might be needed to find the ideal fit though." - Matt Beer
