How to Choose the Best Mountain Bike Helmet

How to choose the best mountain bike helmet

Back in the day strapping a piece of foam to your head looked as bad as it sounds. While the picnic cooler liner has been the bicycle helmet’s mainstay of protecting power since the mid-80s, elements of comfort, convenience, and aesthetics have come so far that today’s MTB skid lids are now as much a fashion statement as a necessary evil.

Choosing the “best” mountain bike helmet is like choosing the best bike — all that really matters is that you have (and wear) one. That said, head shape, riding style, and personal preference means some helmets will be better than others.

“What should you consider when looking for the better helmet?” is the question I will address on the first page, with differences between genres and recommendations on following pages. Whether you’re budget-minded, bold, or baller, I’ve gathered some of the best offerings from a variety of helmet manufacturers. If yours isn’t listed, make a case for it in the comment section below.

Helmet Safety Standards

By law, every bicycle helmet sold in the United States since March 1999 must meet the Consumer Product Safety Commission (CPSC) minimum safety standard. Other certifying organizations have come and gone before 1999 and some (Snell, ASTM, CE) still exist, but are either voluntary stamps of approval or apply in specific applications. Denoting the US certification preference is important because, although the CPSC is widely used throughout the world, some countries have adopted their own standards.

Most standards follow a similar protocol. The helmet is secured to a headform that measures g-force (G) on impact after being dropped one to two meters onto an anvil. Permanent head injury occurs at 400 Gs while 300 Gs produces unconsciousness with possible neurologic sequelae. Helmet straps, amount of coverage, and stability when yanked are also tested.

Photo: Consumer Reports

Perhaps more valuable to the consumer is what a safety standard does not tell you. The CPSC and others set minimum requirements based on data gathered in a laboratory. While you may not suffer permanent brain damage with a helmet, most certifying agencies set the failure threshold at 300 Gs — a force, at the very least, likely to knock you unconscious! The standard also does not tell you how far it exceeds the minimum. Finally, a lab is not a trail and I don’t recall the last time I was able to predict a fall from the height, speed, and temperature onto the surface shape of my choosing.

The take home: no certified helmet can guarantee you won’t break yourself upon any impact.

What is MIPS?

From our MIPS primer, “MIPS is a thin layer of material that goes between your head and your helmet…allow[ing] your helmet to rotate on your head in an impact while still wearing it snugly in normal riding.” The slip plane concept makes sense in theory, but if not executed correctly, does no more than jack up the prices on helmets that are just as safe (and cheaper) without MIPS. Here is a more thorough background on MIPS and I’ve summarized the more salient points on why MIPS may be more fiction than fact.

Image: Scott Sports
  • The slip plane concept requires a full sliding layer that many companies are not employing correctly. The layer interface either doesn’t fully encompass the helmet or fails to provide the appropriate sliding material.
  • The scalp (especially coupled with hair, oil, and sweat) is Mother Nature’s MIPS.
  • Adding a layer for MIPS provokes companies to decrease the EPS liner, which is more important in mitigating head trauma.
  • Overall, there is limited research on MIPS.
  • Rounder, smoother helmets may be just as good as MIPS at providing a slip-able plane.

MIPS won’t make a helmet less safe, but don’t lose sleep if your next favorite helmet doesn’t have it.

Helmet Fit

When it comes to helmets, fit is synonymous with safety, but fit is not standardized under any test. It’s up to you to determine proper helmet fit. The shape of the mold is selected by individual helmet manufacturers, which is why some helmets fit you better than they fit me.

Here are some rules of thumb for fitting a half shell and full face mountain bike helmet:

  • The inside of the helmet should come in contact with your entire head and sit level, just above the brow, without interfering with vision.
  • The one-size-fits-many ring system should be tensioned enough that your scalp moves with the helmet.
  • More expensive helmets have two to three height adjustments for the rear stabilizer to further tune the fit.
  • Straps should be tight enough that the helmet moves no more than an inch from level.
  • Straps meet at a Y that is adjusted just below the ear.
  • When fastened, check the buckle’s strength by giving it a quick tug.
  • If the helmet moves more than an inch or slides over the scalp after the above steps, it may not work for your head.

Due to additional adjustability, finding the right half shell is not nearly as tricky as a full face, which depends on inner pads and a mold that best suits your head.

  • A properly-fitted full face should almost feel too snug. Don’t worry, that squishy foam padding will soon pack out to where it feels just right.
  • Make sure there are no voids between helmet and head.
  • Cheek pads should feel firm enough against your cheeks that you cannot fully puff them out and to the point it makes speaking a little more difficult.
  • With the chin strap fastened, grab the chin bar and rock the full face to and fro; your scalp should move with it.
  • If you plan on rocking a neck brace, take it along to assure compatibility.

Helmet Materials and Construction

Despite the variety of shapes, vent orientation, tensioning systems, and other features, nothing on your helmet is more important than the crushable foam liner sandwiched between the outer shell and your head. Liners are made from beads of expanded polystyrene (EPS) that spread the energy of an impact by deformation, bringing your head to a slower stop. EPS can be tuned to a density that fits the helmet’s application (softer for slow speed impacts and harder for high speed). Some companies employ multiple foam thicknesses to achieve the best of both.

Smith uses a meshwork of rubber straws they call Koroyd to enhance impact resistance. Image: Smith Optics

Without the outer shell we’d all look like we’re packing perishables to a picnic. Besides providing a more agreeable surface for pinstripes and decals, the outer shell protects the crushable liner and provides a smooth surface so the helmet slides along the trail instead of snagging. Entry-level helmets typically have plastic shells glued to the EPS, while higher-end lids bond the shell to the liner in-mold during polystyrene expansion.

iXS putting the X Matter where it matters, seen here in a cutout on the Xult full face

If your budget allows, in-molding is highly recommended for two important reasons. First, by nature of the process, in-mold requires a higher quality shell which better protects you and the EPS liner. Second, because the shell and liner essentially become one, dents are more visible to help you identify underlying cracks in the EPS that would otherwise be masked by dead space between two glued layers.

A new twist on rotational force reduction with Armourgel, used by Kali and the new Leatt Enduro 3.0. Image: KaliProtectives

Beyond the foam liner, straps, and ensuring a proper fit, every other helmet feature either provides more comfort or convenience. These features also happen to be the main reason why a helmet might cost $160 more than a helmet meeting the same CPSC standard. There is no shortage of bells and whistles here, so i’ll address some of the more common features.

Helmet Ventilation

Ventilation ports are strategically placed to draw air in and channel it to exit points, thus cooling by convection. Larger front vents are better at determining a helmet’s ability to cool. Given the density and thickness of the foam liner, the ability to protect your head is always at odds with keeping it cool. Increasing ventilation with either more or larger ports requires a denser foam or liner reinforcement which may actually transmit more g-force to the head on impact. In other words, more vents are not always better.

Image: Fox Racing

Many companies do a nice job explaining away their helmet’s cooling capabilities, but testing is difficult and subject to several limitations. Case in point, a change in head angle of just a few degrees makes a big difference in how air is channeled through vents. Other confounding factors include a proper fit, hair, and sweat.

Convenience Features

By now, you’ve whittled your helmet options to a fairly short list. Just to make matters more difficult, consider the frosting on the cake. While these features should fall low on the list of priorities, they can be the difference between a great helmet and one that is perfect!

  • Removable chin bar: the ability to transform a half shell into a full face is a good fit for those looking for an extra edge, peace of mind, or for those who can’t afford a dedicated DH lid. While a convertible full face does not replace the protecting prowess of the full-fledge full face, it gets pretty damn close, with some even passing ASTM certification.
  • Lens compatibility: Most DH helmets work well with most goggles, but half shell heights, straps, and occipital coverage can make a new helmet purchase turn into a new sunglasses purchase. Take your googles and/or shades along when shopping to make sure they play nice with the helmet(s) you’re considering.
  • Light compatibility: depending on how you rig your night light, take your mounts along to see which vent configuration works better.
  • Visor: inspect the visor and its attachment points for ease of use and potential durability issues. Lower end helmet visors snap into place using small plastic stems, while higher-end helmets offer tool-free screws for adjusting and removing.
  • POV camera mounts: some helmets come camera mount-ready, while most require your own modification. Like lights, if you insist on mounting your camera up top, make sure the helmet is amenable.

A note on aftermarket mounts: Helmets standards discourage anything protruding from the helmet due to risk of snagging. Please ensure that any modification such as a light or camera mount will break free under reasonable amounts of stress.

Bicycle Helmet Buying Tips

  • Due to the importance of getting the right fit, try before you buy if possible.
  • Never buy a used helmet. It’s not possible that the previous owner is aware of hidden micro fractures in the EPS liner.
  • Replace your helmet after a crash. Damage may not be visible to the naked eye, but it’s there.
  • Know your terrain and riding style. Get the right tool for the job.
  • Spend what you need to properly protect your brain. Despite safety and fit being the most important, you need to like it, too!

Mountain Bike Helmet Recommendations

Every year we review a dozen or more of the latest helmets for mountain biking. If you’re searching for the right half-shell or full face helmet, do yourself a favor and check out some of these mountain bike helmets for the safety features and styles that best suit your riding.

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