Smith Bike Helmets: Koroyd, Goggle Integration, and What to Buy
Smith spent decades making goggles before it made helmets, and the eyewear thinking is the most underrated part of the range. The Koroyd marketing needs unpicking first.
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Smith started in 1965 with a goggle. A dentist in Idaho built a sealed double lens with breathable vent foam to stop his own goggles fogging on powder days, and the company grew out of that one problem. Helmets came decades later, and the sequence matters, because the things Smith does better than its rivals are all downstream of forty years spent thinking about what sits on your face.
The two headline features tell that story. The first is eyewear integration: where the goggle strap sits, how far the visor lifts to park them, and a ventilation system designed specifically to pull warm air out of the top of a lens frame so it does not fog on a slow climb. The second is Koroyd, a welded tube structure Smith uses alongside conventional foam, which is marketed hard and understood poorly.
Both are worth taking seriously. Neither is a substitute for the two things that decide a helmet purchase, which are certification and fit. So this guide does the honest version: what Koroyd is and is not, how the lines differ, and what actually justifies the price gaps in the range.
Why the goggle heritage actually matters
Most helmet brands treat eyewear as an afterthought and add a rubber strap grip at the back. Smith designs the two products against each other, and there are three places you can see it.
AirEvac. Smith's ventilation is arranged so that air entering the front vents passes over the brow and exits through the top of the goggle or sunglass frame rather than stagnating there. Fogging happens when warm damp air sits still against a cold lens, which is exactly what occurs on a slow technical climb when you stop generating airflow. This is a real problem that most helmet designers ignore because it belongs to the goggle, and it is the single most useful thing Smith does.
Visor geometry. The trail helmets lift the visor far enough to stow goggles underneath it properly, not just far enough to clear the lens. That sounds trivial until you have climbed for forty minutes with goggles jammed awkwardly on top of a helmet that will not quite hold them.
Sunglass docking. Several road and trail models have defined channels or ports where an arm can slot in when you push glasses up onto the helmet, so they stay put over rough ground. If you ride in changing light and take glasses on and off, this matters more than another 10 grams of weight saving. Our cycling sunglasses guide covers the lens side of that decision.
Koroyd, explained honestly
Koroyd is thousands of extruded thermoplastic tubes, thin walled and welded together side by side into a block, oriented so the open ends face outward. Under an impact the tube walls buckle and crush in a controlled, progressive way. Because the tubes are open, air can pass straight through the block, which is the property that lets a helmet designer put energy-absorbing material where a vent would otherwise have to be a hole.
That is the genuine engineering claim and it is a reasonable one. Smith does not use it as a wholesale replacement for expanded polystyrene. It is bonded into zones within an EPS shell, so what you are buying is a hybrid liner: foam doing most of the structural work, Koroyd occupying areas that would otherwise be open vent.
The right way to judge any specific Smith helmet is the same as for any other brand: check that it carries CPSC certification, check the current independent scoring from the Virginia Tech Helmet Lab, which buys helmets at retail and tests them across multiple impact locations and speeds, and then check the fit on your own head. That table is updated as new helmets are tested, so look it up rather than trusting a number quoted in an article that may be two years old.
Worth noting also that Koroyd is licensed to several brands, not exclusive to Smith. Seeing it in a spec list is not a Smith signature and not a mark of tier.
The Smith helmets worth buying
Smith Session MIPS, Large
- CPSC 1203 certified, MIPS rotational liner
- Koroyd zones bonded into an EPS shell
- AirEvac ventilation aimed at goggle and sunglass fogging
- VaporFit dial retention, three shell sizes across the line
The Session is where the range makes the most sense. It carries the technology that defines the brand, it has the trail coverage that makes a half-shell worth owning, and it usually sells well below its list price, which puts it in the same money as helmets with far less going on. Compared to the Forefront above it you give up some rear coverage, a little visor adjustment range and some pad quality. Compared to a $60 helmet you gain multiple shell sizes, real vent channelling and a retention system that does not need retightening every ride. This is also a sensible choice for anyone on an electric mountain bike, where more descents per ride means more exposure.
Smith Session MIPS, Small
- Small shell rather than a large one cinched down
- CPSC 1203 certified, MIPS liner, Koroyd zones
- Roughly 51 to 55 cm depending on the model year chart
- Same construction and features as the larger sizes
Listed separately because the small shell is a genuinely different object, not a marketing size. A helmet moulded for a small head sits closer to the skull, weighs less and looks less like a mushroom than a medium shell wound down with the dial. Anyone with a measured circumference in the low fifties should be buying an actual small shell, and this is the main practical advantage a multi-shell brand has over a universal fit ring. Smith also runs artist and designer collaboration colourways on the Session that price the same as the plain finishes, so if the graphic version is the one in stock in your size, you are not paying a premium for it.
Smith Forefront 3 MIPS
- CPSC 1203 certified, MIPS liner
- Deeper coverage at the occiput and temples than the Session
- Larger Koroyd area and more aggressive vent channelling
- Adjustable visor with a dedicated goggle stow position
Forefront is the flagship and the coverage is the reason to buy it. The shell comes further down the back of the skull and further round the temples than the Session, which is the region that takes the hit when you go over the back or sideways into a tree. You also get a visor with real adjustment range and pads that hold shape. What you do not get is a different certification, because there is only one and everything in the range has it. Buy this if you ride technical terrain often. Buy the Session if you ride mixed trails on weekends.
Smith Signal MIPS
- CPSC 1203 certified road helmet, MIPS liner
- Koroyd zones with AirEvac airflow through the brow
- Sunglass docking designed into the shell
- No visor, lighter and cooler than the trail models
The road side of Smith is smaller and less celebrated than the trail side, and the Signal is the sensible entry into it. The interesting part is again the eyewear thinking: sunglass docking that holds arms securely when you push glasses onto the helmet, and the brow airflow that keeps a lens from misting on a climb. Weight and airflow are competitive rather than class-leading, which is the honest assessment. If you want the last 40 grams and the deepest vent channels, road specialists build lighter helmets for the money.
The range, line by line
| Model | Job | Koroyd | Standard | Typical price |
|---|---|---|---|---|
| Convoy MIPS | Entry trail half-shell | No | CPSC 1203 | $70 to $100 |
| Session MIPS | Mid trail half-shell | Zoned | CPSC 1203 | $100 to $160 |
| Forefront 3 MIPS | Flagship trail half-shell | Extended | CPSC 1203 | $230 to $270 |
| Mainline MIPS | Bicycle full face, gravity | Zoned | CPSC 1203 and ASTM F1952 | $280 to $330 |
| Persist 2 MIPS | Value road | No | CPSC 1203 | $80 to $110 |
| Signal MIPS | Road, all-round | Zoned | CPSC 1203 | $140 to $180 |
| Trace MIPS | Performance road | Zoned | CPSC 1203 | $230 to $280 |
Swipe sideways to see all columns →
Two things to read out of that table. First, Koroyd is a tier marker within the Smith range rather than a safety marker: the entry models go without it and still meet the same standard. Second, the only row with a second certification is the Mainline, and that is ASTM F1952, the bicycle downhill full face standard. It is a bicycle helmet with a chin bar, which is a different thing from a motocross helmet built to DOT FMVSS 218. If you are shopping for a machine with an engine, you want the latter, covered in the dirt bike helmet guide.
What Smith does better than most
- Genuinely the best goggle and sunglass integration in mainstream helmets
- AirEvac airflow addresses lens fogging, which most brands ignore
- Multiple shell sizes across the range, not a universal fit ring
- Koroyd lets vent area double as energy-absorbing structure
- Session street prices land well under the list price most of the year
Where the brand costs you
- Koroyd marketing implies a safety tier the certification does not create
- Road models are competent rather than class-leading on weight and airflow
- List prices at the top of the range are high against the competition
- The Koroyd tubes trap dust and are awkward to clean properly
- Smaller retail presence than Bell or Giro, so trying one on is harder
How to judge any of them
Three checks, in order, and they apply to every brand on the market.
Certification is a yes or no question. Look inside the shell for the CPSC 1203 marking. It is mandatory for bicycle helmets sold in the US and has been since 1999, it covers impact attenuation onto flat and hemispherical anvils in hot, cold and wet conditioning, positional stability, and retention strength, and it is pass or fail with no grades. Every Smith bicycle helmet has it. So does every legally sold competitor.
Independent scoring is where helmets actually separate. Because the federal test produces a pass rather than a number, the only public data that ranks one certified helmet against another comes from independent labs. The Virginia Tech Helmet Lab is the one to read, since it buys retail helmets, tests multiple impact locations at multiple speeds, weights both linear and rotational effects, and publishes a star rating. Look up the current table for the exact model and model year you are considering rather than trusting a general claim about a brand.
Proprietary systems are engineering, not evidence. MIPS is a licensed low-friction liner aimed at rotational forces in angled impacts. Koroyd is an energy-absorbing tube structure. Both are plausible. Neither is a certification, and neither tells you how a specific helmet scored. Take them when the price difference is small and ignore them when they are being used to justify buying a helmet that fits you worse.
Fit and eyewear integration
Measure with a soft tape around the widest part of your skull, roughly an inch above the eyebrows and ears, and buy to that centimetre figure against Smith's chart for the model. Because Smith moulds multiple shells rather than stretching one, sitting between two sizes is worth resolving carefully: take the smaller shell and let the dial open if the pads still clear your head comfortably, since a smaller shell sits closer, weighs less and moves less.
Then the standard checks. The front rim about two finger widths above your eyebrows, not tipped back on the crown. Side straps meeting in a V just below and slightly forward of the earlobe. One finger under the chin strap and no more, with the helmet pulling down when you open your mouth wide. Grab the shell and try to roll it forward and back; if it moves independently of your scalp, tighten first, and if that fails the shape is wrong for your head.
The Smith-specific step is to bring your eyewear. Put the goggles or glasses on first, then the helmet, and check three things: that the goggle strap sits flat in the channel without riding up, that the brow pad does not push the top of the frame down onto your cheeks, and that the visor lifts far enough to stow the goggles when you climb. If you wear a large frame or a prescription insert, this check is the whole reason to buy this brand rather than another. The general procedure is in helmet sizing, fit and safety ratings.
Which Smith is yours
If you ride trails on weekends and want one helmet that covers most things, the Session is the answer and the price it actually sells at makes it easy. If you ride technical terrain regularly, or you race enduro, the extra coverage on the Forefront is a real difference rather than a spec sheet one. If you ride lifts and bike parks, the Mainline and its ASTM F1952 certification is the category you want, not a half-shell.
On the road side, the Signal is the sensible middle and the Persist 2 is the value option if you can live without Koroyd, which you can. If you commute on a fast ebike, note that a road helmet is not the ideal shape, because impact energy scales with the square of speed and extended coverage models exist for exactly that reason. That case is made in the ebike helmet guide, and if you are unsure how fast your bike will actually sustain, the class explainer settles it before you shop.
For the category view across every brand, start with the bike helmet buying guide. If you like the idea of a brand built around a single design idea, POC does the same thing with injury reduction, and Fox is the comparison worth making if your riding leans further toward gravity and dirt.