Smith Mainline Helmet Review

Smith’s full-face mountain bike helmet offers loads of coverage in a very comfortable, stout, and lightweight package

Author: Erik Nilson / Updated: May 19, 2023

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First impressions are important, and the Smith Mainline’s stout feel and low weight make it a hard helmet to forget. From the get-go, the Mainline impressed me with its premium set of features and exceptional comfort. After many downhill laps, some burly enduro rides, and a few shuttle days, I continue to be smitten with the Smith—the Mainline is one of the best all-around full-face helmets currently available.

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Smith Mainline Helmet

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Unboxing the Smith Mainline

Unboxing the Smith Mainline was a standard affair. Inside the relatively thin cardboard box, you’ll find the helmet wrapped in plastic and held in place by open-cell foam blocks. Although the packaging is relatively minimalist, it does an adequate job of protecting the Smith during transport. Like most premium helmets, the Mainline comes with an array of extras. For dialing in the fit, you’ll find three thicknesses of cheek pads, two different sizes of neck pads, as well as two different liners. Smith also includes a couple of visor bolts, along with a handy travel bag to keep the helmet from getting too scratched up while rolling around the back of your car. The Smith’s $310 price tag, which may be a little tough to swallow, is in line with its competitors and those included extras help ease the pain a bit.

Smith Mainline Performance

Protection and Safety

I’ll be the first to admit that I don’t spend a ton of time in a full-face helmet–I typically ride in half or 3/4-shell models. However, I’m always impressed by the sense of security that full-face helmets provide, and the Smith Mainline is no different. The helmet feels exceptionally stout in hand–much more so than the Troy Lee Designs Stage–and the overall coverage it provides is quite high. Every time I slip on the Mainline, I can’t help but feel that the helmet is urging me to pull up for that long triple, hit that corner a little fast, or stay off the brakes for just a second longer. If you’re coming from a half-shell helmet, I can guarantee you that you’ll feel considerably more protected in the Mainline (for better or worse).

In terms of safety, the Smith Mainline ticks all the boxes. The helmet features a MIPS liner that’s said to reduce rotational forces on the brain during a crash, and it utilizes Koroyd, which crumples and absorbs energy upon impact. Further safety measures include a hard polycarbonate shell and the use of EPS foam throughout. All of these features contribute to the Mainline’s CPSC CE EN 1078, ASTM F1952 downhill, and NTA-8776 E-Bike certifications. I actually went over the bars while shooting photos for this article and I’m happy to have ridden away unscathed. Despite expertly spearing the ground with my head, the direct impact felt like more of a sliding sensation and not a jarring hit like I would have expected. I’m not sure if this was the MIPS liner speaking or just the nature of the crash. Nevertheless, I’m happy with the protection it provided me.

Comfort and Fit

When it comes to full-face helmets, the Smith Mainline stands out as one of the more comfortable options I’ve used. I ordered a size medium helmet for my slightly roundish 57 cm head and am pleased with the results. After experimenting with the different size pads and liners–something I highly recommend you try–I landed on the thin liner, large neck pad, and medium size cheek pads. With this combo I was able to achieve a snug fit that stayed in place on gnarly downhill trails, yet remained comfortable during multi-hour enduro style rides. It’s worth noting that the padding, liner, and chinstrap of the Mainline are exceptionally soft and comfortable, something that was noticeable right out of the box, especially when compared to other models, like the Fox Proframe RS.

Ventilation

In the realm of full-face helmets, the Smith Mainline is one of the better options I’ve tried when it comes to ventilation. I can easily stay comfortable climbing in temperatures in the low 60s (at a slow pace), and during shuttle days when I’m just bombing downhill, it’s easy to push that to 70 degrees. As soon as I get up to trail speed, air easily flows through the 21 vents. And the massive chinbar holes do a great job of letting fresh air hit my mouth and face. While the Mainline does breathe well overall, it’s hard not to mention the use of Koroyd in the vents (the plastic straw looking things), which does inhibit airflow a bit. For those who pedal a lot or prioritize a well-ventilated full-face above all else, then the slightly breezier Troy Lee Designs Stage may be worth a look.

Goggle and Glasses Compatibility

Just as you’d expect from a full-face mountain bike helmet, the Smith Mainline pairs well with a variety of goggles. I had success riding in both the Giro Blok as well as Smith’s Squad model, and neither pair of goggles caused any issues. They fit well within the confines of the helmet and they didn’t lift off my face. However, I did notice that the straps cover a few of the main vents and inhibit airflow in the process. This didn’t really pose any problems for me as there is still plenty of fresh air entering the helmet, but it’s noteworthy nonetheless. And while I rarely–if ever–ride in a full-face with glasses, I had no issues with my favorite pair at the moment (the Tifosi Sledge Lite).

How Much Does the Smith Mainline Weigh?

One thing that impresses me most about the Smith Mainline is its combination of low weight and just how stout it feels. My size medium weighed in at 1 pound 12.1 ounces on my scale, which puts it right in the middle of the lightweight full-face spectrum. It’s possible to go lighter (the feathery Troy Lee Designs Stage weighs 1 pound 4.4 ounces) and you can easily go heavier as well (the new Fox Proframe RS weighs 1 pound 13 ounces). And just for comparison’s sake, a standard full-face helmet like the Giro Insurgent Spherical weighs 2 pounds 4.7 ounces. In the end, the Smith Mainline deftly balances weight and protection.

Key Features of the Smith Mainline

MIPS Liner

Most modern mountain bike helmets feature some sort of slip plane technology aimed at reducing rotational forces during a crash, and the Smith Mainline uses the industry standard MIPS system for such purposes. The liner integrates nicely into the helmet, and doesn’t block any vents or catch on long hair.

That said, it’s one of the louder implementations of this technology I’ve experienced–even while spinning around the parking lot it’s easy to notice a squeaking noise coming from the helmet. Thankfully, the noise completely fades into the background once the trail points down. In my attempt to pinpoint the source of the noise (and because I’m a serial tinkerer), I placed small pieces of paper between the MIPS liner and EPS foam throughout the helmet. This in turn eliminated all squeaking sounds. I don’t recommend you try this (because safety and liability, etc.), but it’s something I hope Smith addresses in future versions.

Koroyd

One of the first things you notice when looking at the Mainline is those small straw looking things that are placed in some of the vents. Officially called Koroyd, this technology uses polymer tubes that are thermally welded together to form a network of energy-absorbing material. Upon impact, the tubes claim to compress and crumple in a controlled manner, reducing the force transferred to the head and minimizing the risk of injury. I didn’t see much real-world data to back up these claims, so it’s hard to say how well it works, but I’m all for attempting to increase head protection.

D-Ring Buckle

A tried and true way to secure your lid, the D-ring buckle on the Smith Mainline certainly inspires confidence while strapping in. It may not be quick to use or as fashionable as magnetic Fidlock buckles, but the system works well and certainly feels a bit more robust than a plastic version. It even includes a little snap to secure the end of the strap from flapping in the wind. All said, I have zero complaints with the metal D-ring closure.

Visor

I don’t typically get too excited about visors, but Smith really nailed the Mainline’s. The adjustable visor is nicely sized and effectively blocks dirt, mud, and debris, while simultaneously offering plenty of range for whatever the conditions require. I also really like the overall shape and size of the visor, and in my opinion, the square profile and length are perfect. Finally, it doesn’t seem to inhibit airflow, and the material is robust enough to prevent shaking or rattling at high speeds, yet flexible enough to bend instead of break upon impact (which I had the pleasure of testing).

Issues with the Smith Mainline

Noted above, my main complaint with the Smith Mainline is the noisy MIPS liner. In the parking lot it’s nothing short of annoying, however, its saving grace is that it goes unnoticed once you point your bike downhill. Other than that, the Mainline has remained problem free and I continue to be impressed by its durability and robust construction every time I take it for a spin. As always, I’ll continue to log miles in the helmet and report back if something crops up.

The Bottom Line

The Smith Mainline is a special helmet. It’s strong and robust, and it inspires tons of confidence, yet every time I pull it off the shelf I’m impressed with how lightweight it feels. While there are full-face helmets that are lighter and more breathable and others that offer a bit more protection, there are very few, if any, that bring everything together as well as the Mainline. Overall, it does an excellent job of remaining lightweight while offering great protection. In the end, I think it’s one of the best all-around full-face helmets on the market.

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How Does it Compare?

Smith Mainline vs. Troy Lee Designs Stage

If you’re considering the Smith Mainline then there’s a good chance the Troy Lee Designs Stage is also high on your list. Both helmets feature a MIPS liner, are lightweight and vent relatively well, and each includes a number of pads for dialing in a nice fit. They’re also rated for DH use and come in a handful of good-looking color options. The TLD Stage weighs about 3 ounces less and has more vents, which makes it the better option for those earning their turns. However, the Mainline feels considerably more stout and has a more premium fit and finish. In the end, I think the Stage is better for pedally rides whereas I grab the Mainline for lift assist or shuttle days.

Smith Mainline vs. Fox Proframe RS

Another popular choice for a lightweight full-face helmet is the Fox Proframe RS. Like the Smith, the Fox features a MIPS liner and adjustable visor, and it comes with different size pads for getting the right fit. Additionally, both helmets are DH certified and feel a bit more robust when compared to lighter weight options like the TLD Stage mentioned above. In terms of ventilation and weight, they feel about the same (although the Fox does weigh about 2.5 ounces more than the Smith). That said, I find the Mainline to have a more premium fit and finish than the Proframe RS. And the Smith looks and feels more streamlined on the trail. In the end, I prefer the more comfortable and plush Smith Mainline over the Fox Proframe RS–and it also doesn’t hurt that the Smith is about $50 less than the Fox.

Smith Mainline vs. Giro Switchblade

One final option to consider is the Giro Switchblade. The Switchblade is a bit different from the Mainline in that it’s a convertible helmet. The chinbar can be removed for long climbs and then reattached before dropping in. There’s also the option to run it without the chinbar altogether, which splits the difference in terms of protection between a half-shell and full-face helmet. The Switchblade debuted in 2016 and was a popular choice for many years. However, by today’s standards it’s quite heavy and doesn’t ventilate very well, and the MIPS liner is noticeable and pretty loud on the trail. For full-face use, I much prefer the more comfortable Smith Mainline for its premium build, ability to remain cool while charging downhill, and more streamlined looks.

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