Thursday, November 16, 2023

Merrell MTL Skyfire 2 Matryx Multi Tester Review: Basically Perfect for Intended Purposes! 8 Comparisons

Article by Jeff Valliere and Renee Krusemark

Merrell MTL Skyfire 2 Matryx ($210)


Jeff V:  The Merrell MTL Skyfire 2 Matryx is Merrell’s flagship lightweight race shoe with the MTL stands for Merrell Test Lab. It features a Matryx kevlar fibers upper, FloatPro dual density midsole foam, Flexplate and 5mm Vibram Megagrip high performance outsole. It weighs in at just 8.1oz / 230g in my US men’s sample size 10.  The Skyfire 2 is a serious contender for any shorter, fast, technical trail races/PR attempts.


Light, fast, stable, agile, secure, protection, traction: Jeff V/Renee


Could use a touch more cushioning in the heel, but a VERY minor nitpick: Jeff V

Lack of cushion (not really a con; for its shorter faster purposes the cushion works): Renee


Approx. Weight: men's 7.6oz  / 215g (US9)  /  women's 6.17oz / 175g (US8)

  Samples: men’s 8.1 oz  /  230g US10 // women’s 6.56 oz / 186g US8

Midsole Stack Height: men’s 25mm heel / 19mm forefoot (6mm drop spec) 

Approx Full Stack Height: 31.5mm heel / 24mm forefoot  (6mm drop spec) 

$210 Available March/April 2024

First Impressions, Fit and Upper

Jeff V:  Merrell!!??!! What?  I will admit that my exposure to Merrell has been very limited and have not taken the brand very seriously from a trail running or running standpoint as I relate the brand to being a leader in the hiking boot industry.  

When Skyfire 2 arrived, at first I thought the box was empty, it was so light.  The moment I pulled them out of the box and onto my feet, I was impressed by the no nonsense race ready look and knew this shoe would be a hit.  T

he Matryx upper combines multi filament threads of Kevlar and high tenacity polyamide, creating a single layer of material that is lightweight, with better breathability and abrasion resistance.  

The Skyfire 2 fits true to size, with a secure heel, midfoot and forefoot, the whole doing an excellent job of providing a flexible, minimal, breathable and secure upper.

While the upper has a very secure and race like fit, there is enough wiggle room in the toe to feel comfortable/not confining and allow for a bit of swell and splay.  I have pushed the Skyfire 2 Matryx fast on technical trail descents, off trail, off camber-foothold and stability were excellent.

Breathability is very good, with excellent air flow. The toe bumper is minimal, but offers just enough protection from minor dings, but overall the upper is not very protective and  this can be an issue in talus and choss.

Lacing is secure and it is easy to achieve proper lockdown,  first try.  Merrell also adds a lace loop here that is much higher than all other lace loops I have seen.  

At first I was a bit thrown off by this placement, however after a few tries at optimal positioning, I think it makes sense.

The heel counter is somewhat thin and flexible and has an internal strip of padding inside at mid height, yet also is perhaps a bit rigid, requiring a bit of break in.  

The padding helps, but is a touch pronounced and not particularly soft.  I noticed a bit of rubbing on my heel on one of my very early and super steep uphill runs, but that discomfort seems to have gone away without any real consequence.  Softening this a bit though would help I think.  The collar height is just right for me, but I do find that the design easily allows in trail debris.  I would love to see a light stretch “gaiter” (or higher collar) as the Hoka Zinal 2 has to keep out debris.

The tongue is gusseted in a very wrap around manner, cradling the foot which keeps the tongue well centered and adds to the overall great fit and security of the shoe. To note the inner black linings are treated with 37.5 natural mineral based temperature regulating technology. 

Renee: Like Jeff, my running experience with Merrell is limited, and by limited, I mean this is the first Merrell trail shoe I have ever run! The Spring 2024 releases look fantastic, and after running in the Skyfire 2 Matryx (and the upcoming Morphite), I think Merrell’s plan to become a respected brand in trail running is working. 

The Skyfire 2 Matryx is a good looking shoe, and initially I thought it might be “too technical” of a shoe for my mediocre paces on non-mountain terrain. However, I had a lot of fun in them running on woodland single track (about 180 feet of gain per mile) and doing hill repeats in uneven/rugged fields.

The upper is race-oriented in terms of security, yet I found it to be accommodating and comfortable for training runs. 

The platform looks narrow, but the fit is not. I have a regular width foot (low volume), but I do like a roomy toebox and forefoot. The balance between a secure trail shoe and comfort with the Matryx Kevlar upper is great. I thought the shoe would feel like a cleat, but it really just disappears on foot while running. My first run was hill repeats in a soybean field (very uneven) and I thought the frozen stalks would pierce the upper. While I did have some damage to the exposed sections of the outsole, the Kelvar upper had perfect protection. Jeff makes a good note about the lack of a toe bumper, but for my terrain, it worked well. The upper is breathable, and when running through snow I could feel the cold (although with wool socks on, it wasn’t an issue). 


Jeff V:  The FloatPro midsole consists of a two part dual density foam that is light, resilient and responsive.  Merrell tells us there is no supercritical type foam in the mix. Sitting between the two FloatPro midsole layers is the Flexplate, a BZM-8 Rislan engineered rock plate with we think 8% fiberglass fill, produced from a renewable source.  The midsole is light and responsive and with the Flexplate, provide enough cushioning and protection to blunt hard landings on sharp rocks and roots and have enough give for several hours of fast running in technical terrain. 

The midsole here is on the somewhat minimal and light end of the spectrum and while not plush by any means, feels surprisingly well cushioned and not harsh or overly firm. It is perhaps a middle of the road density that balances cushion, protection, performance and predictable stability.  

Also of note, the footbed is essentially non existent in line with the stripped down, minimal nature of the shoe.  I have tried adding a thicker insole in order to add just a bit more cushioning (only because I just want to run in them more and longer), but found that throws off the fit of the shoe and ended up abandoning that idea.  If you want a bit more, perhaps opt for the Merrell Long Sky 2, which has that little bit extra you might be looking for. Overall, the midsole feels light, airy and really fun!

Renee: Jeff covers the details. The shoe is meant for distances less than 25k, so the cushion is minimal, but not hard or uncomfortable. The complete underfoot feel is perfect for fast efforts, and I think the shoes work best for “sky” runs or running steep ups and downs. That said, I’m not running rocky, mountain terrain. 

I was surprised at how well the midsole and ride worked for hill repeats in a field and on woodland single track trails, which, comparatively, aren't remotely close to the vertical gain of mountain runs. My longest effort with the shoes was 145 minutes, and my feet felt great. I wouldn’t choose the shoes for running on flat, hard surfaces, but for short spurts on that type of terrain, it’s a fast shoe too. 


Jeff V:  The Vibram Megagrip outsole with 5mm lugs provides exceptionally good traction on a wide variety of terrain and conditions.  The lugs are aggressive directional chevron shaped and the outsole has a lattice like design with the intention of minimizing weight and perhaps at the same time increasing flexibility (though I think much of that is more influenced by the FlexPlate).  

There are also 12 perforations on the top of the lugs (8 in the forefoot and 4 in the heel), presumably to add screws or hobnails for traction.  I have not tried this, as I have not found the need given my use of the shoe, but the option is there.  

I have been able to test on all my usual Boulder  trails, steep rocky technical, off trail, loose off trail and off camber, rock slabs, wet, dry, fresh snow, packed snow and even some icy-ish packed snow and I always felt confident in my footing.  So far, durability is proving to be average to above average.

Renee: I concur with Jeff. The lugs are 5mm and well spaced, which make for great traction. I ran through snow, slush, mud, leafy trails, and a few sections of packed dirt. The outsole adds to the “fun” factor of the ride, allowing for confidence when running inclines and going fast on the declines. I did have minor issues of mud becoming lodged in the cut-outs sections, but the shoe is so lightweight that the ride is not affected.

I have some minor damage to the exposed sections of the outsole after running on frozen soybean stalks, but I’ll add that the shoe works great for off trail terrain. 

Ride, Conclusions and Recommendations

Jeff V:  The Sky Fire 2 is one of the most exciting shoes I have run in in a long time and certainly one of the biggest surprises.  

The ride is fast, exciting, lively, dynamic and is overall is just a blast on the trails.  They are so much fun despite them being a lightweight racer and on the minimal side, I find myself wanting to run in them all of the time.  I’ll definitely reach for them in the future when I am feeling like a spirited run in the range of up to 3 hours (which is about the max for this shoe), and for PR attempts or shorter races.  

While the Sky Fire 2 is an ideal pick for going all out fast on a wide variety of mountain terrain, no matter how rugged, I would however exercise caution in loose scree and talus, as the upper is pretty stripped down and offers little protection when mixing the choss.  

My longest run in them was a 13.3 mile run over 3 local summits, with over 4,400 feet of gain (and loss).  This run had a mix of everything, very steep technical trails, cruiser singletrack, dirt road and some scrambling, with some snow and ice mixed in for good measure.  The Sky Fire 2 handled this run perfectly, though by the end of the run (3 hours), I was wishing for a bit more cushion (though I was perfectly fine up till about 2.5 hours).  

Merrell has really knocked it out of the park with this shoe and I cannot wait to get my feet in other models of their trail running line.

Jeff V’s Score:  9.8/10

Ride: 10 - for the intended purposes and distances, the ride is amazing!  Fast and well cushioned/protected for such a light shoe.

Fit: 9.8 - Amazing secure fit from Matryx upper, but I think heel could be improved a bit.

Value: 9.8 - $210 is pricey, but you are getting exceptional,  top of the line, performance

Style: 9.5 - The look is racy, sharp and eye-catching.

Traction: 10 - for such a minimal shoe and design, traction is great everywhere I run.

Rock Protection: 9.5 - for such a light and minimal shoe, rock protection is excellent.


Renee: Kudos to Merrell for making a shoe that is fun and exciting. I’m always interested to read what my fellow RTR runners think of shoes, especially if they run different terrain than I do. Jeff is running mountain terrain, and I’m running in fields and woodland single track. The fact that the Skyfire 2 is fun on these varied terrain types is a testament to its design. The ride is exciting, secure, and fun. 

The shoe will work best for short, fast efforts especially when inclines and declines are steep or constant. The $210 price is hefty, but with its Kevlar upper, Vibram outsole, and lightweight, I think the shoe is priced comparative to its competition. I’m inclined to say it’s best for racing in mountain/steep terrain, but I enjoyed it for training runs in fields and woodland terrain. For its intended purpose, the Skyfire 2 Matryx is basically perfect.

Renee’s Score: 9.8/10 (-.20 cost)


8 Comparisons

Index to all RTR reviews: HERE Roadtrailrun 

MTL Long Sky 2 Matryx (RTR Review)

Editor’s Note. Jeff and Renee did not test the Long Sky.  It weighs 8.6 oz  / 244g (US9) so 1 oz /28g more, we assume mostly due to its fuller coverage outsole but also maybe due to a different FloatPro foam. It shares a Matryx upper with the Skyfire.

It has a 1.5mm lower heel and 0.5mm higher forefoot, so it is a 6mm drop shoe. It has no nylon plate as the Skyfire has and has a single density foam midsole. Its platform is almost identical with only the midfoot being 5mm wider. At $160 it is $50 less expensive than the Skyfire. Mike Postaski in his review scored them the same Jeff and Renee did the Skyfire 2 at 9.8 /10.

Hoka Zinal 2 (RTR Review

Jeff V:  The closest comparison I think, the 2 shoes are very close in weight with advantage going to Sky Fire 2 as they have comparable fit, security, fast/nimble/agile performance, traction, etc…  

The Sky Fire 2 offers a bit more performance I think, with an edge in response, a little better traction and is a little more adept in technical terrain with better protection and cushion underfoot.  The Zinal has a slightly more protective upper and I LOVE the snug stretch mesh around the ankle collar to keep debris out.  Not sure why all trail shoes do not have this?  Zinal is $30 less.

Salomon S/Lab Pulsar SG (RTR Review)

Jeff V:  Aside from the Pulsar SG being lighter, I cannot think of any reason to pick it over the Sky Fire 2.  The Pulsar SG does have a more glove like custom feeling upper, but it is really snug and unforgiving for all but the shortest runs with no leeway for wiggle room.  Because of its lower weight, the Pulsar SG might be a slightly better choice for all out uphill efforts, but if you have to come back down (which we often do), the Sky Fire 2 has better traction, better cushion, better protection.

Salomon Pulsar Pro 2 (RTR Review)

Jeff V:  Much of the above comparisons on the S/Lab Pulsar SG holds true, though the Pulsar Pro 2 weighs a good bit more and despite having more cushioning, the cushioning is hard and unforgiving.  I will also mention that the Pulsar Pro 2 feels particularly tippy with the inflexible plate and narrow heel.

VJ Spark (RTR Review)

Renee: Both shoes are meant for short, fast distances and have a look that reminds me of a cleat. The Skyfire 2 is a much lighter shoe. Sizing is comparable, although the toebox of the Spark is a bit shallow. The midsole of the Spark has a bit more softness, but still not enough for long distances. Overall, the performance of the Skyfire 2 is better, albeit at a much higher cost. 

Jeff V:  Agreed with Renee, but I think the Sky Fire 2 has better cushioning and protection underfoot, at least on the rocky terrain I frequent.  Spark has a better outsole with even better traction.

VJ XTRM 2 (RTR Review)

Jeff V:  See Spark comparison above.  While the XTRM 2 is a better shoe IMHO than the Spark, many of the same comparisons hold true.

TNF Vectiv Sky (RTR Review)

Jeff V:  The Vectiv Sky is not as light, nor is it as agile or adept in technical terrain and although it has a similar stack and  fit and feels more firm and less forgiving, maybe due to its carbon vs  the nylon plate of the Sky Fire.  The Sky Fire 2 is quicker overall, more responsive and has better traction.

NNormal Kjerag (RTR Review)

Jeff V:  Close in weight, fit, comfort and performance, both are great options for fast trail running/racing.  The Sky Fire 2 I find to be a bit more protective with the plate and for sure has better traction and I think a bit more responsive uphill.

New Balance SC Trail (RTR Review)

Renee: The SC Trail has a carbon plate and is a higher drop shoe at 10mm vs. 4mm for the Sky Fire. For runners needing more cushion, the SC Trail might work better (the shoe is heavier, but still light weight for a trail shoe). The Skyfire 2 is the better choice for rugged terrain or steep inclines and declines. The plate of the SC Trail will help with speed on mellow terrain (while not being unstable elsewhere despite the high drop). Sizing is comparable. 

Jeff V:  Agreed with Renee on all points.  

The Skyfire 2 Matryx will be available March-April 2024

Tester Profiles

Jeff Valliere loves to run and explore the mountains of Colorado, the steeper and more technical the better. He has summited all of the 14ers in the state and can be found on mountain trails daily, no matter the weather, season, conditions or whether there is daylight or not.  On the side he loves to ski (all forms) bike and hike, often with his family, as he introduces his 12 year old daughters to the outdoors. Jeff was born and raised in New Hampshire, but has called Colorado home for over 25 years. He is 5’9” and 145 lbs.

Renee is a former U.S.Marine journalist, which is when her enjoyment of running and writing started. She isn’t that awesome of a runner, but she tries really hard. Most of her weekly 50-60 miles take place on rural country roads in Nebraska, meaning mud, gravel, dirt, hills, and the occasional field. She has PR’s of 1:30:59 for the half marathon and 3:26:45 for the marathon.

Samples were provided at no charge for review purposes. RoadTrail Run has affiliate partnerships and may earn commission on products purchased via shopping links in this article. These partnerships do not influence our editorial content. The opinions herein are entirely the authors'.

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Mike P said...

Jeff V- You also noticed the lace loop - I liked the higher placement in the Long Sky 2 as well.

arnop said...

It's so frustrating cause we know they are a banger but we have to wait....