Smith Mainline Helmet Review


Words by Robert Johnston  |  Photos by Adam Lievesley

As bikes get more capable, more people are riding gnarly and fast terrain than ever before. But there’s only so much a capable bike can do for you, and crashing is an unfortunate inevitability of our beloved sport. A helmet is fundamental, as are knee pads for many, but body protection is often overlooked. The main thing to blame for this is the typically bulky and uncomfortable protection of the past, which made a day in the saddle a terrifying prospect. Thankfully these days we have protective materials, such as D3O, that can provide impressive protection without adding bulk and excessive heat into the equation. Aimed at offering riders an attractive option to wear on everything from trail rides through to eMTB missions, the Bluegrass Seamless D3O range is a grand departure from the storm trooper suits of the past. But would this convince the Eurowolf to wear body protection more often? Read on to find out.


The Bluegrass Seamless B&S D3O body armor is quite self-explanatory – it’s a torso garment with protection for the back and shoulders provided by D3O inserts. It’s targeted at the trail, enduro and eMTB crowd who are looking to protect these vital areas from damage in a crash without adding too much bulk and heat or restricting movement. The main component of the top is a “seamless”, highly stretchy base layer-style garment constructed from Dryarn material. This material features 10% Elastane to provide the stretch required to achieve the next-to-skin fit on all body shapes, allowing it to be a unisex garment that is only offered in two sizes – S/M and L/XL. It is extremely long in order to allow it to be tucked into the waist of your legwear and prevent it from riding up. In key areas the top is ventilated thanks to a highly open mesh, giving the critical strength and rigidity only where it’s needed and allowing the remainder to breathe as well as possible. The material is a quick drying microfiber that is designed to draw moisture from the skin and regulate body temperature, with a treatment to minimize bacteria and odor buildup. In the back are two small pockets designed to store soft items such as a snack or energy gel. Providing the protection are three D3O inserts – a D3O® BP4 L1 back protector and two D3O® T5 EVO X L1 shoulder inserts, which are all removable for washing. Bluegrass claims the back protector is more ventilated and flexible than ever before, and the shoulder shells are pack-compatible to suit riders looking to carry supplies for their ride. The Bluegrass Seamless B&S D3O retails at €250/£225 ($310 approx.), and Bluegrass also offers a similar item, the Seamless lite, that loses the shoulder protection to further reduce the heat and restriction for €190/£170 ($230 approx).


Pulling the Seamless B&S D3O out of its packaging for the first time, I was relieved to feel how soft and stretchy the material was and how neat the finish was – after all, it better be good at that sort of money. Pulling it on (in the literal sense thanks to its very slim natural shape that’s only made possible thanks to its incredible elasticity), the result after a little bit of wiggling of the shoulder and back pads to get them into the most natural spot is the feeling of a soft base layer with a little extra weight in the protected areas. It’s seriously comfortable. Contrary to Bluegrass’s model shots for the Seamless range, you don’t need chiseled abs to wear this comfortably. However, the mesh designs aren’t the most flattering and it feels rather embarrassing to wear on its own in the car park when you don’t have said abs – the lace look isn’t for everyone. But then it’s not designed to be on show after all, so performance will come first here. A slightly loose-fitting jersey went over the top with absolute ease, so I tried it instead with a tighter fitting number which also went on without issue – the D3O inserts are impressively form-hugging themselves and aside from the very top of the back insert there’s essentially no edges to snag on the jersey as you pull it on. The low-profile padding does add a little thickness, but the only takeaway from others once you’ve donned a jersey are suggestions you’ve not been skipping shoulder day at the gym. There’s not the same Quasimodo look from the back protector or any sharp edges poking through a jersey that other protectors can give.


In use, the Seamless B&S sits firmly put thanks to its near compression fit, which makes the D3O pads feel like a second skin and lets the whole suit fly very much under the radar. After a very hot and sweaty day of uplift, the only slight hint of discomfort was on the edge of one shoulder pad, which I believe to have stemmed from using it as a cushion against the seat of a rough tractor uplift. In use, including some mid-length enduro pedals, there wasn’t so much as the slightest bit of chafing or discomfort. It certainly adds heat over running the jersey alone, as you’d expect, but outside of the D3O covered zones it’s no hotter than a thin base layer, and the D3O zones aren’t exactly boiling hot either. This means I ended up running the protector for a few days pedaling, when expecting some gnarlier terrain or in an enduro race. This is truly the first body armor I’ve personally tried where I would consider this, which says all it needs to about its comfort in use. The only impact testing was a couple of light impacts with my shoulder and trees on tightly lined trails, which the D3O fended off admirably. With D3O’s solid reputation for protection that exceeds expectations, I’m sure the back protector would perform equally admirably when called upon, too. It’s a shame there’s no option for chest protection within the same range, but of course this would detract from that breathability that makes it so pleasant to wear.


When it comes time to remove the Seamless B&S after a ride, it’s a tough task when you’re still a little damp, with the close-hugging material tending to stick firmly in place. Leaving it on for a little while after as you dry off made things easier though, and the instances where I was determined to rip it off immediately after the ride didn’t cause any damage to the thin material, which was impressively durable given its lack of bulk. The same went for those tree-scuffing incidents, which the armor shrugged off without leaving a mark to tell the tale. Popping the pads out of the jersey is easy to do for washing, making things dry out much quicker. Going against the recommendations of Bluegrass I did stick the jersey through the washing machine a couple of times to see if there would be any ailments, and it held up just fine, but of course you’d do this at your own risk of destroying your pricey protective gear. Speaking of which, the price of the Seamless B&S D3O is a bitter pill to swallow, but for a piece of protective gear that encourages you to wear it for more rides than normal because it’s so comfortable, it may repay that initial outlay in volumes by saving an expensive medical bill.

The Wolf’s Last Word

The Bluegrass Seamless B&S D3O body armor provides valuable protection without the typical discomfort of bulky protectors, letting enduro and even some trail mountain bikers ride with protection that could save a nasty injury. If you can justify the cost, then it’s one hell of an addition to your kit bag.

Price: €250/£225 ($310 approx.),

We Dig

Breathes well
Low profile protection

We Don’t

Mesh hides nothing


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