Smith Mainline full-face helmet review

Smith’s Koroyd-loaded open-face helmets are super popular for their excellent fit and enhanced protection but does the brand-new Mainline full-face perform as well for ‘full-send’ specialists?

Smith Mainline full-face helmet
(Image: © Guy Kesteven)

BikePerfect Verdict

Great fit and stability once you’ve tuned the padding, easy breathing and excellent build quality, goggle syncing and Koroyd protection. Ventilation while riding is restricted though and it’s easy to accidentally knock the cheek pads out


  • +

    Super stable fit

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    Enhanced Koroyd protection

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    No breathing interference

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    Easy pad tuning

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    Clear goggle venting

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    Great build quality


  • -

    Poor cooling airflow

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    Pop in pads can pop out

  • -

    D-rings are a pain to use

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Smith introduced a totally new style and protection direction when the Forefront open-face trail/enduro lid and the stable, almost universal fit and enhanced Koroyd protection broke cover. It an instant hit with more hardcore riders. Constructing one of the best full-face mountain bike helmets around was an obvious next step but Smith has really taken its time to transfer all those advantages into a full-coverage helmet. Koroyd’s honeycomb always means ventilation/cooling issues and pop out pads can be irritating.


The Mainline is built from multiple hardshell segments (chin bar and temples, crown, brow, midsection and lower rim are all separate pieces. The inner shinguard gets a firm leatherette construction that looks a lot like car dashboard material. The EPS body is augmented with Koroyd shock-absorbing honeycomb that fills the side crown vents and the gallery of big exhaust windows around the back. The front three shinguard vents, the centre top vent and three lower nape exhaust vents are open though and there are two more ‘AirEvac’ vertical brow vents designed to pull steam out of your goggles.

There’s a brain-protecting ‘floating’ MIPS liner and instead of a cradle, you get two thicknesses of cradle and back section pads, two different neck rolls and three depths of chin pad to tune the fit. The pads also use antibacterial silver thread embedded X-Static/XT2 hybrid material. DH approved security is completed with a double D-ring strap with thick fleece padding and a press stud double back strap tidy.

Unsurprisingly given that Smith is primarily an optics brand the rear is recessed to anchor goggle straps and the adjustable visor can be tipped right up to leave goggle storage room underneath. Overall build quality is excellent, too.


At just over 800g for the medium, weight sits right between heavier Bell and Leatt competition and lighter Troy Lee and Fox options. Sizing is slightly smaller than most and like most ‘proper’ DH helmets there’s no cradle for an instant dial-in fit fix. Switching pads around lets you fine-tune fit (we ended up with thinnest cheek, crown and neck pads but thicker rear pad.) and the basic shape worked really well with everyone who tried the helmet. The floating MIPS liner inevitably means some movement and it can creak too, but our sample didn’t suffer as much from that as other reviewers and users. While we’ve no scientific evidence of our own to back up Koroyd’s claims of increased impact absorption we know several riders who’ve seemingly survived serious head slams better than they expected using Smith helmets and who now won’t use anything else.

Vision is excellent with minimal peripheral interference and goggle syncing is just as good. The EvacAir vents genuinely seem to help reduce steaming, too. There’s plenty of airflow through the chin guard with its big mouthpiece and we never suffered from stale air bouncing back even when sprinting hard. There’s a noticeable draught down the helmet sides, particularly if you’re not using goggles.

Heat radiates out well once you’ve stopped -there’s a lot more heat to get rid of than a helmet with better through-flow while you’re riding. That meant we were more likely to take if off on hot climbs at which point the ease with which the pop stud secured chin pads unpopped meant we nearly lost them a few times. It’s easy to pull off the small Velcro pad anchoring tabs if you’re not careful too. While it’s a DH requirement the D-ring buckles are a faff to use compared to snap or Fidlock buckles, but that obviously applies to other helmets as well.


Fit, stability, visibility and build quality of the Mainline are excellent, price and weight are competitive and anecdotal evidence suggests Koroyd really can help reduce impact severity.

Breathing is unrestricted and it radiates heat OK when stopped or going slow. Goggle integration is also first class. Ventilation on the fly is definitely below par though and pad loss and MIPS creak are other potential problems.

Tech specs: Smith Mainline full-face helmet

  • Price: £275 / €300
  • Weight: 803g (medium)
  • Colours: Matt sage/red rock (tested), Rocky Mountain Enduro Team, matte black
  • Safety: MIPS - CPSC, CE EN1078 and ASTM F1952 (Downhill)
Guy Kesteven

Guy has been working on Bike Perfect since we launched in 2019. Hatched in Yorkshire he's been hardened by riding round it in all weathers since he was a kid. He spent a few years working in bike shops and warehouses before starting writing and testing for bike mags in 1996. Since then he’s written several million words about several thousand test bikes and a ridiculous amount of riding gear. To make sure he rarely sleeps and to fund his custom tandem habit, he’s also penned a handful of bike-related books and talks to a GoPro for YouTube, too.

Current rides: Cervelo ZFS-5, Forbidden Druid V2, Specialized Chisel, custom Nicolai enduro tandem, Landescape/Swallow custom gravel tandem

Height: 180cm

Weight: 69kg