Article by John Tribbia, Phil Royer, and Adam Glueck
Salomon S/Lab Pulsar 4 ($220)
Editor’s Note: We are thrilled to welcome Phil Royer to the RTR Test Team for his first review. Based in the Boston area, Phil is a former track runner at Dartmouth, a 2:18:53 marathoner, 2023 US 50K Trail Champion, and was 3d at the 2025 Gorges Waterfall 100K world mountain championships qualifier race. Phil's full run bio is at the end of the article.
Introduction
John: Salomon's S/Lab division has long been at the forefront of trail running innovation, consistently delivering footwear that meets the exacting demands of their elite athletes and dedicated trail enthusiasts. Building on the legacy of its predecessors, the S/Lab Pulsar 4 emerges not just as an update, but as a significant evolution. This shoe aims to redefine speed on rolling and technical terrain, offering a potent combination of unmatched lightness, enhanced propulsion, and crucial stability.
The Pulsar 4 is engineered for athletes who demand the pinnacle of performance, particularly those eyeing records in short to mid-distance races, from challenging SkyRaces to iconic events like the Mont-Blanc marathon (20km to 80km). Salomon’s engineers, in close collaboration with athletes like Rémi Bonnet - who reportedly broke a Strava record on Mont-Veyrier during his first test run - have meticulously crafted a shoe that offers a road-racing sensation with all the necessary trail-specific technologies. It’s designed to be more inclusive than the Pulsar 3, promising to suit a broader range of runners without sacrificing its high-performance, technical edge.
Adam: I’ve enjoyed running in shoes from Salomon’s S/Lab division for a long time, specifically due to their excellent uppers, fantastic grip, and responsive and lightweight midsoles.
Salomon made a shoe called the S/Lab Sense Ultra which I ran in extensively in 2018. It was based on their super light S/Lab Sense short distance racing shoe, but added a little bit more stack height and protection. In later iterations, these gained more weight and complexity and became a full ultra distance racer (see the S/Lab Ultra 3 for example), but I loved how the original S/Lab Sense Ultra kept the light and responsive feel of a short distance racer, while adding just enough protection for long runs on technical terrain. After I wore out that shoe, putting in hundreds of miles of trail running in the hills above Geilo Norway, I missed the unique combination of lightweight responsiveness and distance capability. The S/Lab Pulsar 4 feels like a reimagination of the original S/Lab Sense Ultra, but with the latest foam, upper, and outsole technology to create one of my favorite trail shoes of all time.
Pros:
- Lightweight and cushioned John / Adam
- Responsive, energetic, and protective ride John / Adam
- Excellent grip on various surfaces John / Adam
- Stability and precision allows for fast running on rocks, roots, and snow Adam
- Secure and breathable upper John / Adam
Cons:
- Narrow fit may not suit all feet (but wider than the Pulsar 3) John / Adam
- Price point John
Most comparable shoes
Salomon S/Lab Pulsar 3: Phil/John
Hoka Zinal: John/Adam
Stats
Approx. Weight: unisex 9.03 oz / 255g US unisex 9
Sample Weights:
men’s 9.31oz US M10 (Phil), 9.03 oz / 255g US9 (Pulsar 3: 7.15 oz / 202g US9)
Stack Heights:
Pulsar 4: 34 mm heel / 28 mm forefoot, (4mm drop)
Pulsar 3: 29 mm heel / 23 mm forefoot ( 6mm drop)
Platform Widths:
V4: 85mm heel / 76mm midfoot / 110mm forefoot
V3: 76mm heel / 60mm midfoot / 100mm forefoot
First Impressions, Fit and Upper
(Phil) Overall, no surprises in the fit. A bit wider toe box than the S/Lab Pulsar 3, but still holds the foot in place well with the low profile and snug lacing.
The lacing system with a tuck-away pouch is still super quick and handy (why don’t they all do this?). The tongue and ankle lock certainly feel much stiffer than the S/Lab Pulsar 3, which is by far the most noticeable difference in the upper.
Time will tell how much this changes as it breaks in. I had no problems with the collar on the Pulsar 3, but it seems like that friction would be reduced now so if you did have issues you should see a marked improvement on this new iteration.
John: Unboxing the S/Lab Pulsar 4, the first impression is one of refined purpose. It feels exceptionally light, a hallmark of the Pulsar line. This is achieved through a combination of Salomon's new dual-foam midsole and the industry-reference Matryx upper.
The Matryx upper is immediately recognizable, woven with aramid fibers (like Kevlar) that provide incredible tear resistance, support, and breathability in a featherlight package. Compared to the Pulsar 3, the fit feels subtly refined.
The new collar construction is a welcome change, offering a more comfortable and accommodating hold around the ankle, which should appeal to a wider range of foot shapes.
The overall feel is a secure, tailored, sock-like fit that conforms to the foot without constricting it, crucial for dynamic movements on uneven ground. My experience on the familiar Fern Canyon trail in Boulder, which demands precision, highlighted how well the upper locks down the foot.
The shoe comes with Salomon's signature QuickLace system, always offering a reliable, fast, and easy way to make on-the-fly adjustments. I always appreciate this feature and its resistance to snagging on trail debris. While S/Lab shoes often lean towards a narrower, performance fit, the Pulsar 4, while still precise, feels like it might accommodate slightly more volume than the already snug Pulsar 3, though those with very wide feet should still approach with caution. Sizing felt true to my standard US Men's 9.
Breathability, a strong suit of the Matryx material on the Pulsar 3, remains excellent. During my test runs up Bear Peak, where temperatures have been fluctuating this spring with rainy days and warmer days, my feet remained comfortably cool. The platform also features a Profeel Film (an internal TPU layer) which, combined with the toe cap, offers good protection against rocks and sharp surfaces without adding bulk or compromising flexibility.
Adam: I’ve greatly enjoyed running and racing in a variety of shoes from the S/Lab Pulsar (and prior S/Lab Sense) series. While they’ve always been light weight with refined uppers, the two most noticeable changes I picked up were one of improving the protection and control of the shoe.
Compared to the original S/Lab Pulsar, the upper has more structure, with a sock-like fit. I have had no issues with chafing during testing, and the fit is precise over rocks and roots.
Midsole & Platform
Phil: The great “super shoes on trails” debate rages on, and Salomon is making an intriguing contribution with this latest salvo. It sounds like the team studied the problem with the respect it deserves, and intentionally decided to forego a carbon plate in both this latest Pulsar and the S/Lab Ultra Glide. At the slower speeds of mountain running and with the added requirement of handling gnarly terrain with all tendons intact, there is a strong argument to be made that it is the foam we really need, and not the carbon plate. This is compounded by the fact that we are mostly on soft, uneven ground, which is never going to give us the kind of carbon bounce we get from the smooth roads of Berlin or Sacramento.
This update to the Pulsar certainly leans more into that foam focus, and the result seems very promising. The added stiffness and bounce from the improved foams seems to boost the uphill efficiency even beyond that of the Pulsar 3, which was already a heavy favorite judging by the sea of red at the USA Vertical Champs last year at Loon. There’s enough softness to blunt harsh impacts on steep downhills, yet the ride remains connected and nimble. The stack height is increased but still medium compared to the way things seem to be headed, but that’s a tradeoff in favor of precision and control — a reminder that not all trail shoes need to be moon boots.
In short, this iteration of the Pulsar doesn’t just follow the “super shoe” trend — it reframes it for the realities of mountain running. The result is a midsole that feels not just fast, but purpose-built for competitive vertical terrain.
John: The midsole is where the S/Lab Pulsar 4 truly distinguishes itself from its predecessor and showcases Salomon’s “Super Foam” innovation. It features a DUAL-FOAM construction:
optiFOAM+ (Red Foam): This is the top layer, sitting directly under the foot. It's a “super foam” made from a PEBA and EVA mix, designed to deliver a super dynamic, propulsive, and responsive experience with ultimate comfort.
optiFOAM (White Foam): This forms the bottom unit of the midsole, a lightweight and cushioned EVA foam engineered to ensure stability, especially in technical sections.
This combination gives the shoe a stack height of 34mm in the heel and 28mm in the forefoot, maintaining a 6mm drop. This is a notable increase in stack compared to the Pulsar 3 (29mm/23mm). This gives more cushioning and protection for slightly longer efforts and was noticeably more supportive to my achilles on inclines.
The midsole design also features “Active Chassis” sidewalls that rise up to cradle the foot, enhancing stability and guidance, keeping the foot “like a train on rails.”
Offering a significantly broader base than the Pulsar 3 (+9mm at the heel, +16mm midfoot,,+10mm forefoot), the platform enhances stability for navigating challenging, rocky terrains, yet maintains a streamlined profile that ensures agility for swift, weaving movement.
On the trail, the difference from the Pulsar 3’s firmer Energy Foam is quite noticeable. And despite being considerably heavier, the Pulsar 4 offers a distinctly more cushioned and energetic ride, making the shoe feel light on foot comparably. The supercritical optiFOAM+ top layer provides a noticeable bounce and responsiveness, reminiscent of top-tier road racing shoes, while the underlying optiFOAM layer prevents the shoe from feeling mushy or unstable on uneven terrain. In my tests on a mix of mellow trail to technical trail with steep inclines, the propulsion was evident, and during technical descents, the increased cushioning absorbed impact effectively without sacrificing ground feel entirely, thanks to the Profeel Film.
Interestingly, Salomon has consciously chosen not to include a carbon plate. Their rationale is that a plate’s efficiency boost is most significant at sustained high speeds, and its benefits diminish on slower uphill sections or varied trail terrain where it can even increase ankle strain. For a shoe designed for dynamic, undulating trails, this approach makes sense, allowing the foam and shoe geometry to do the work.
Adam: I resonate with Phil’s perspective here. When bringing road super shoe tech to the trails, I’ve seen different brands (and even different shoes within a brand’s portfolio) take fundamentally different approaches. These road super shoes tend to use 3 primary ingredients, stack height, a low density high energy return foam, and a carbon plate.
Salomon has taken the high energy return foam, but eschewed the carbon plate and kept the stack height lower than some other middle to ultra distance trail shoes. They’ve shared research about how a carbon plate doesn’t provide significant benefit at the speeds seen in trail racing, but what convinced me was running in the Pulsar on more technical terrain.
On light trails and fire roads in California, terrain that I frequently will wear road shoes om, I found the optiFOAM+ super foam midsole to be cushioned and energetic. It’s on the firmer side, but this makes the shoe responsive, and especially as a taller and more powerful trail runner, I really enjoy that it feels controlled and precise over just squishy. There’s no sense of harshness, and the shoe has a stable, predictable, and responsive ride. Even on the road the shoe is light enough and foam propulsive enough that it still rides great.
When I took the Pulsar running on technical terrain, with roots, wet rocks, downed trees, stream crossings, melting snow, and singletrack, I was incredibly impressed by the stability and responsiveness of the midsole.
The lack of rocker and plate allow for precise foot placement with inconsistent stride length and cadence. When combined with the precise upper and technical grip, the Pulsar provides sufficient protection for the mountains with an amazing sense of control, and as soon as you are able to open up your stride, the energetic bounce of the midsole is genuinely propulsive.
Outsole
Phil: The lugs feel like a middle ground for moderate grip on a decent range of surfaces. More depth would be nice for soft ground, but would make slick rock and roots quite precarious. Less would be just fine for our friends out on the manicured tracks of some west coast trails, but wouldn’t fly here in New England.
John: The S/Lab Pulsar 4 utilizes an All Terrain Contagrip outsole, engineered for confidence across a wide variety of surfaces.
Pulsar 3 (Top) Pulsar 4 (bottom)
A key update here is the significantly larger ground contact surface area compared to the Pulsar 3. This means more lugs are in contact with the ground at any given time.
The lug depth is 3.5mm, slightly less than the Pulsar 3’s 4mm lugs. My testing on mixed terrain - from hardpack to loose scree and rocky scrambles - supports this. The shoe felt incredibly sure-footed. The increased contact area provided a more consistent and reliable purchase on the ground, particularly noticeable when transitioning across different surfaces or contouring on off-camber sections. The grip inspired confidence, allowing for aggressive cornering and braking. I did encounter some slipping when navigating wet rock, but most outsoles would struggle with those conditions with the exception of maybe VJ or La Sportiva.
Adam: I was really impressed with the outsole grip of the Pulsar. I tested this both on wet roots and rocks, snow, dry gravel, fire road, and pavement. Under aggressive acceleration, turning, and decelerating, it’s up there with the best outsoles I’ve tested, including in snow and mud. It won’t have the bite of something with huge soft ground lugs, but the compound, pattern, and surface area make it remarkably effective.
Ride, Conclusions and Recommendations
Phil: The Pulsar 4 has a fun and reactive ride, which is great for the technical trails this shoe is made for, but far from a super-shoe when it comes to bounce. The wider base contributes to improved stability, and the new foam delivers a lively, efficient takeoff. The forefoot hold is a bit more relaxed than the predecessor, but is more than adequate for gripping the trail on all but the most precarious surfaces.
I took these out for one tuneup and then raced in them for the first time at Sunapee Scramble (June 1st, 2025). They performed admirably on a gnarly course with mud almost to our knees at points, and the outsole was adequate for all but the steepest, slickest sections. The added stack height was nicely balanced by the increased width, so I felt plenty of stability even on the roots and rocks.
I foresee continuing to use this as a shorter distance racing shoe for steep and technical routes in the 3 to 10 mile range. The stance is a bit more aggressive and the foam is not as soft as I would prefer for a longer marathon plus distance, but I could see stretching it if you really wanted the improved ground feel on a very difficult course. Overall, the build quality feels high-performance, and the Pulsar 4 delivers a clean, responsive ride that feels like a natural evolution of what this shorter distance category should be focused on. Here in the Northeast, we have tons of races like Sunapee where this feels like just the right balance, and I look forward to letting them rip some more!
Phil’s Score: 9.2 /10
Ride: 9 (poppy and fun)
Fit: 9.5 (Wider toe box should work better for most)
Value: 8.0 (Bit limited use for the price, but you do get what you pay for)
Style: 10 (eye candy for sure)
Traction: 8.5 (medium depth, nice balance)
Rock Protection: 10 (solid outsole layer and ample foam)
Smiles: 😊😊😊😊
John: The ride of the Salomon S/Lab Pulsar 4 is a masterclass in balanced performance. It takes the agility and speed inherent in the Pulsar DNA and infuses it with a new level of dynamism, comfort, and stability. The shoe feels incredibly nimble and encourages a quick turnover, yet the dual-foam midsole provides a more forgiving, energetic, and wider platform than the Pulsar 3. This makes it suitable for a broader range of distances and potentially more runners.
The “road-like sensation” Salomon aimed for is certainly present in the responsiveness and energy return from the optiFOAM+, but it’s expertly blended with trail-specific stability and grip. On steep climbs, the shoe felt light and efficient, and on technical descents, the combination of the grippy outsole, stable midsole platform, and protective upper allowed for confident, fast-paced running. The increased cushioning is a significant boon, reducing fatigue over longer fast efforts without detaching you completely from the trail.
The S/Lab Pulsar 4 is a remarkable evolution. It successfully makes the Pulsar line more accessible by offering increased cushioning and stability, yet it does so without diluting its core identity as a high-performance, race-ready speed weapon. The dual-foam midsole delivers on its promise of dynamism and comfort. The refined upper and more confident outsole complete a package that feels both incredibly capable and surprisingly versatile for fast-paced trail endeavors. The price increase is justifiable given the complete redesign, more complex DUAL-FOAM construction, and the inclusion of premium “super foam” materials.
John’s Score: 9.7 /10
Ride: 10 (energetic, protective, and outstanding up + down)
Fit: 9.5 (but only because I noticed some bunching on the top of the foot)
Value: 9.5 (road / trail crossover for hybrid use; great shoe for non-racing )
Style: 9.5 (I really like the classic Salomon red/white)
Traction: 9.5 (great shoe, but struggled in wet conditions)
Rock Protection: 10 (stable, protective, and cushioned)
Smiles: 😊😊😊😊😊
Adam: The Salomon S/Lab Pulsar 4 is my new favorite trail shoe, especially for more technical terrain. Adding stack height and a more responsive foam, while still keeping the light weight, precise upper DNA from prior Salomon racing shoes creates a solution so versatile and fun I’d grab it for anything from a vertical kilometer to a 20 mile hike. I think Salomon took the right elements from a road shoe, specifically the energetic foam and light weight, while removing the comprosies on stability and technical terrain by keeping the geometry un-rockered and plate free. It’s a classic trail shoe recipe, executed brilliantly with some of the best technology available.
Adam’s Score 9.8 /10
Ride: 10 (energetic, protective, and outstanding up + down)
Fit: 10 (but only because I noticed some bunching on the top of the foot)
Value: 9 (great shoe for both racing, training, and hiking, not sure on long term durability)
Style: 10 (The red and white screams fast)
Traction: 9.5 (great for the lug depth, in mud and snow may struggle due to shallower lugs)
Rock Protection: 9.5 (stable, protective, and cushioned, if the protection was any greater it may compromise the precision and agility)
4 Comparisons
S/Lab Pulsar 3 (RTR Review)
John: The Pulsar 4 elevates the experience with a new dual-foam midsole, offering significantly more dynamism and cushioning than the firmer Pulsar 3, making it more versatile for longer fast efforts. While both share a precise Matryx upper and excellent grip, the Pulsar 4 aims for a broader appeal with increased comfort and stability without sacrificing its race-ready speed (despite being a little heavier). I’ll run in the 4s until they fully break down and then use the 3s as a backup :)
Hoka Zinal
John: The Pulsar 4 offers a more premium, “super foam” feel with its dual-density midsole, providing a bouncier and more energetic ride compared to the Zinal's more traditional responsive cushioning. Both are agile and lightweight, but the Pulsar 4 focuses on a road-shoe-like propulsion with trail-specific grip, while the Zinal offers a reliable, nimble feel for fast trail efforts.
Hoka Zinal 2 (RTR Review)
Adam: I love the Zinal 2 as an everyday middle-short distance trail shoe. The Zinal is light, responsive, feels good on road, and has a very comfortable upper. The Pulsar 4 offers a much more protective outsole for anything with rocks and roots, and more responsive midsole material. I think the Zinal is slightly more comfortable due to the less structured upper, but for technical trails or racing, the Pulsar 4 will now take my top spot.
Brooks Catamount Agil (RTR Review)
John: The Pulsar 4 provides a more cushioned and energetic ride due to its PEBA-blend foam and higher stack, contrasting with the Catamount Agil’s firmer, more direct, and lower-to-the-ground feel optimized for extreme agility and short, fast bursts. While both are exceptionally lightweight and precise, the Pulsar 4 offers more underfoot protection and versatility for slightly longer distances.
The North Face Vectiv Sky (RTR Review)
John: The Pulsar 4 delivers its propulsion through an innovative dual-foam midsole without a plate, offering a more adaptable and cushioned ride compared to the Vectiv Sky’s firmer, carbon-plated, and more aggressively rockered experience. Both target speed on technical terrain, but the Pulsar 4 emphasizes foam-driven energy return and a slightly more forgiving feel, while the Vectiv Sky relies on its plate for a more rigid and propulsive toe-off.
The S/Lab Pulsar 4 will release June 2025
Tester Profiles
Philip Royer (5’11”, 150lbs) is a trail and mountain runner who still mixes it up with some road racing now and then. He ran for Dartmouth College back in 2010 to 2013, and has slowly transitioned to longer road races, then trail and mountain as he learns to appreciate the finer things in life. He snuck in a win at the USATF 50k Trail Championships in 2023, but just missed the Olympic Trials Marathon qualifier with a 2:19 in 2024. The dream is to get under the standard next time, and find a way to get one of those Team USA trail jerseys mailed to his place in Boston, because he is sick of hearing them get sent out to places like Boulder and Bozeman. His dog Bekele is the fastest runner he knows, with PRs of 3:11 in the mile and 12:33 in the 5000m.
John Tribbia (5' 6", 130lbs) is a former sponsored mountain/trail runner who has run with La Sportiva, Brooks/Fleet Feet, Pearl Izumi, and Salomon. Even though he competes less frequently these days, you can still find John enjoying the daily grind of running on any surface, though his favorite terrain is 30-40% grade climbs. He has won races such as America's Uphill, Imogene Pass Run, and the US Skyrunner Vertical Kilometer Series; and he's held several FKTs on several iconic mountains in Boulder, Colorado and Salt Lake City, Utah. If you follow him on Strava, you'll notice he runs at varying paces between 5 minutes/mile to 12 minutes/mile before the break of dawn almost every day.
Adam Glueck (6’0 205 lbs) is a trail and mountain runner currently based in California. He recently graduated from Dartmouth College in 2022, where he competed in Nordic Ski racing, racing in NCAAs twice and on the national Supertour and international Ski Classic Marathon circuit. When he’s not engineering, Adam now races trail running over distances from 5k to 50k, and you’ll find exploring new trails from Yosemite to Moosilauke to Marin to Hong Kong.
8 comments:
Following
Sounds like the show has lost its purpose, I don't want a high stack height heavy shoe, there are other options. The greatest trait of this show had been the extreme light weight and nimble footing. Time to stock up on the 2 and 3, I will not be buying the 4.
Thanks for this great review, but I feel like you disagree on the ideal distance for a race.
I love my Merrell Long Sky 2 Matryx and my TNF Vectiv Sky 2. Can you say whether the Salomons are suitable for longer distances or not?
Thank you very much.
you have to laugh
Our multi-tester review approach allows us to offer a range of perspectives, highlighting how different individuals experience the same product. This is particularly valuable because gear preference often comes down to personal needs and running styles.
For example, I generally prefer a lower-profile shoe. However, I've found that a shoe like the Pulsar 4, with its enhanced cushioning, can be a great option for longer distances, even while maintaining agility and performance. While my personal ultra-long distance running has become less frequent, this illustrates that what works best truly depends on the individual user. Our aim with multi-tester reviews is to provide readers with a comprehensive understanding of a product's potential, helping readers determine if it aligns with their specific preferences.
If possible pls compare to S/LAB GENESIS
This sounds like a great shoe but should have been marketed with a different name after gaining 3 ounces and a big midsole. The original Pulsars offered a uniquely light shoe that I could use for events up to 50km.
Maybe Salomon has a replacement planned for it with a different name.
Ok, thanks for the answer
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