Saturday, April 11, 2020

Merrell MTL Skyfire Review: Something New! A great value, comfortable riding, fast and light trail runner

Article by Jacob Brady and Canice Harte

Merrell MTL Skyfire ($100)


Weight: 9oz / 242g

  Samples: 10.5oz / 298g US Men’s 12

Stack Height: 23.5mm/17.5mm; Drop: 6mm; Lug: 5mm

Available Now. $100


Jacob: The MTL Skyfire is a lightweight, medium-cushion, versatile trail shoe “designed to go fast in the mountains”. Merrell describes the Skyfire as “stripped-down” and “race-ready”. The Skyfire is intended for sky races and shorter (<50km) mountainous races with the companion Long Sky for longer runs and races (RTR initial review). The focus of the Skyfire was to keep weight low but to provide a protected enough trail shoe capable of the most technical terrain. 



Energetic, lightly bouncy, smooth and fast ride

Enjoyable on all terrain at all paces

Great value; versatile

Balanced cushioning: good protection and ground feel


Great ground feel

Lots of traction

A nimble and quick shoe that is also comfortable



Narrow forefoot (helps precise foot placement but lowers comfort and accessibility to wider feet).

Laces are a bit thick, rough, and hard to untie

Needs a tight lace up for good midfoot/heel security.

Canice: Nothing obvious. I could nit pick a few things but there are no glaring cons

Tester Profiles

Jacob runs a mix of roads and trails in the Portland, Maine area. He runs every day and averages 50 miles per week. Jacob recently ran a PR 2:51 marathon and just wrapped up his first season of ultra/trail running which included two 50km trail races and two mountain races.

Canice is a 2 x finisher of the Wasatch 100, the Bear 100, Moab 100, Western States 100, and Leadman as well as many other ultras. He regularly competes in Expedition Length Adventure races with his longest race to date 600 miles as well as in traditional road races and triathlons.

First Impressions and Fit

Jacob: I was unfamiliar with Merrell’s trail line prior to receiving the MTL Skyfire and had had no information about its intended use until midway through my testing. Thus I had no starting point for testing: what terrain to take them on, would they be good for road-to-trail runs?

Jacob: Out of the box the Skyfire is visually simple with a solid color mesh and no overlays—not a polished or highly-engineered look, but cleanly minimal. The Skyfire feels lightweight in hand and on the foot, with a moderately narrow toe box and a looser midfoot/heel fit, but good sizing overall. The midsole is softer than expected and pretty flexible . Aside from the narrowness it’s a light, balanced-feeling shoe. 

Canice: I like lightweight shoes with good ground feel and these shoes are both light and have plenty of ground feel. Additionally I was struck by the cushioning of the midsole. Sometimes with light shoes that have good ground feel they can have a harsh ride, but the Merrell MTL Skyfire’s offer plenty of cushioning for the longest of trail runs. This is clearly subjective but give them a go and you’ll see what I mean.

Canice: Jacob and I have not met but I was reading his comment about the toe box feeling narrow. I’m guessing Jacob must have wider feet than me. I measure as medium on a brannock (The device that measures your size in stores) device, and I had plenty of room in the forefoot. My toes can splay out and I don’t feel any pinching on the sides. Given our two different experiences I would say if you’re medium to narrow you’ll be good and if you’re on the wider side of medium you’ll want to check the fit. As for people with wide feet, this shoe will not work for you.


Jacob: The Skyfire upper uses a two-layer mesh, reinforced with a TPU “supportive structure cage” to aid in security and lock-in. The outer mesh is a thin and high-abrasion fishnet material with very large holes, not much support from this layer and extremely breathable. The inner mesh is thinner still but a tighter weave. There are more layers and support around the heel, including a rigid heel counter. The tongue is gusseted, connected to the inner mesh layer and the laces are stiff and hard to untie. Multiple times I was unable to untie them with frozen hands, but thus they’re unlikely to come untied accidentally. The upper is very breathable but water and mud enters too readily and it is very cold/the wind blows through in cold weather.

Jacob: The Skyfire has an intentionally snug fit as foothold is critical in its intended application of technical mountain racing. Thus it fits a bit narrow in the toe box, which I have not found to cause issues and contributes positively to the shoe’s ability to hold the foot on precise landings. Often the toe box is the weaker point for security in a trail shoe, but in the Skyfire it is the midfoot. There is not quite enough structure in the midfoot or heel collar for me to get great foothold for running fast unless I really crank down the laces. Then, it is less comfortable, but not problematic on shorter (<10mi) runs, and would be worthwhile for racing. 

Breathable mesh is a noticeable characteristic of the MTL Skyfire 

Canice: Jacob addresses the details very well so I’ll cover this from an overall perspective. The upper feels soft yet durable and is incredibly breathable. The MTL Skyfire has great mid-foot hold and plenty of room in the toe box and the heel counter is soft and well cushioned yet holds your heel securely in place. I find the protection across your toes to be soft and flexible. The gusseted tongue is well padded and the flat laces stay tied as you would hope.

In the photo above you can see the reinforcements along the eyelets and the padded tongue.


Jacob: The midsole is a single slab of EVA with a 3/4-length rock plate that is quite flexible. I did not notice the plate at all until Merrell released more information on the Skyfire and I started trying to feel it. The midsole is straightforward in look and feel, but it hits a perfect balance of cushion, being low and on the firm side, but soft enough with adequate protection for most sub-ultra distances. The midsole is “just” EVA, but it’s uniquely lightly springy and very energetic, which is especially notable on firmer terrain (and road). It’s not a traditional “dead” foam at all.

Jacob: The midsole has a good level of torsional flex: it’s natural and feels flexible, again, I couldn’t even tell it had a rock-plate at first, but the plate keeps it from bending too far around roots/rocks. Thus protection from sharp roots and rocks is muted. While there is enough foam to give some energy return and bounce, the Skyfire is thin enough to provide good ground feel and a quick and connected ride. Great, simple and effective midsole design from Merrell.

Canice: I agree with all of Jacob’s comments regarding the midsole. For my part I like that the MTL Skyfire midsole has plenty of cushion yet remains light and flexible. The midsole also has just enough spring to it to keep it lively on the trail. Sometimes simplicity is a good thing.


Jacob: The Skyfire outsole uses Merrell’s new rubber compound called Quantum Grip, designed to “grab” (quoting Merrell) but also keep weight to a minimum. The rubber is full coverage, flexible, and somewhat soft with very spaced-apart 5mm chevron lugs. There are no lugs in the midfoot and the lugs are shallower near the toe, thus grip on softer surfaces like mud isn’t great, but they shed mud well. The lack of midfoot lugs hasn’t been a particular issue though, has the benefit of cutting weight, and likely contributes to the great road running feel of the Skyfire. 

Jacob: Dry grip is solid, snow/ice grip is surprisingly great, but I’m mixed on the wet grip. Though I’ve had no particular issues it’s not notably confidence inspiring. Despite being designed for racing, which can often mean lightweight but not durable, the Skyfire shows no concerning wear after over 60 miles, at least a quarter of which were on pavement. Overall, the grip is solid, durability is at least average, and the ride/feel provided by the outsole is top-notch. 

Canice: Here in the mountains of Utah it’s the time of year when we’re running a mix of snow and muddy sections of trail combined with dry rocky high desert trails. The MTL Skyfire had all the traction I needed and kept me feeling secure while holding my pace over varied terrain.


Jacob: The Skyfire has a balanced ride that is well-cushioned and energetic as well as stable, low to the ground, and natural. It does not feel at all harsh or hard on any terrain, including asphalt, despite a mid/low stack height and rock plate. The Skyfire is comfortable on easy runs and at slower paces but also conducive to running fast and smoothly. Merrell says, “when you put it on your turnover increases”, and I really felt this. I’d feel lackluster before a run but ever run in the Skyfire ended up being fun and my pace faster than I expected to go that day. I’ve liked almost every run I’ve done in the Skyfire; I even did all-out sprints on pavement at the end of a run and had great fun.

Jacob: As I’ve mentioned throughout the article I had no information about the Skyfire’s intended use when I started testing and found it exceptional on all runs including those with large sections on the road. I received the Skyfire for testing in the winter in New England when the singletrack trails were packed ice—unrunnable without spikes of some sort—and the roads/and sidewalks a mix of ice and snow. Thus my first several runs were around the city with a mix of snow, ice, and pavement. The Skyfire was great for this as it felt very energetic and lightly bouncy on harder surfaces, ran smoothly on the road, and had great snow/ice grip.

Jacob: As the trails melted and I could take it on exposed dirt, the Skyfire was a perfect candidate for door-to-trail, road/trail mix runs. It’s quite capable, if not at home on the ungroomed, heavily rooted singletrack of New England, which I can only say of around half of the nearly 15 trails shoes I’ve tested in the last year. I’m missing two pieces of testing, which is dry, rocky/sandy trail (which I don’t have in NE), as well as mountainous terrain with long descents, however, I feel like they’d perform well on both. They have just enough cushion in the heel to stay comfortable on longer descents and have good grip and feel on all terrain I’ve taken them so far.

Canice: The “Ride” of the MTL Skyfire is best characterized as having lots of ground feel and plenty of cushion. The shoe is springy and lively when you want it and secure in tight technical trails.

Conclusions and Recommendations

Jacob: Overall, the Skyfire is a great lightweight, versatile, all-terrain trail shoe. It has a stable, balanced, and energetic ride which is conducive to smooth running at any pace and is great at speed. It is designed for technical terrain and runs well on tough, rooted singletrack but is enjoyable on paved road as well. At $100 MSRP it has exceptional value.

I’d recommend the Skyfire to all runners. Seasoned trail runners would find value in a peppy shorter-distance (<15mi) shoe for workouts, racing, or just an impromptu free run. Road runners looking for a do-it-all trail shoe or road-to-trail shoe should consider the Skyfire. The aspect which most limits its appeal is its slightly narrow forefoot, so those with wide feet may have issues, unless they’re intending to use it as a short-distance racer only. Overall, I was quite impressed by the Skyfire and will definitely keep it in my rotation as a trail workout shoe, general road-to-trail choice, and a technical, short (<10mi) distance racer.

Jacob’s Score: 8.6

Ride: 9 (30%) Fit: 7.5 (30%) Value: 10 (10%) Style: 8 (5%) Traction: 9 (15%) Protection: 9 (10%)

Canice: The MTL Skyfire is a fun and lively high performance shoe that is equally at home on the race course or in the mountains on your favorite training run. The more I run these shoes the more I love them. They’re definitely in my daily rotation now and I look forward to many more miles in them.

Canice’s Score: 9.4 /10






Rock Protection

Overall Score

Percentage of Total

















Index to all RTR reviews: HERE

Merrell MTL Long Sky (RTR initial video review)

RTR Editor Sam is reviewing the Long Sky. It has an approximate weight of 9.65 oz / 274 g so about half an ounce heavier than the Skyfire with a stack height of 27.5mm heel / 19.5mm forefoot, 8mm drop so 3mm more stack at the heel and 2mm more at the forefoot. It shares the lively midsole foam, has a very mild (not noticeable) medial post with no rock plate as the Fire has, and substitutes Vibram MegaGrip for Quantum Grip. It is the longer run sibling to the Fire.

Inov-8 Roclite 290

Jacob: The Roclite sounds like it would be a similar shoe as it has a flexible rock plate, mid-low stack, lightweight design, and versatile lug pattern. However, my experience with the Roclite was that it had a dead feel and was harsh on most terrain, compared to the lively, surprisingly cushioned Skyfire. Though less ideal on technical terrain, the Roclite has a much more accomodating fit, slightly sloppy in the toebox. Otherwise the Skyfire is superior in all regards.

Saucony Peregrine 10 (RTR Review)

Jacob: The Peregrine has a very similar usage and feel to me, being versatile with good grip on most surfaces and smooth running on the road; a do-it-all trail shoe. The Peregrine is race-able as well, though it is much (nearly 50g in my US M12) heavier. This weight isn’t as noticeable on the run as it sounds, but it doesn’t feel like it adds much comfort over longer distances or protection compared to the Skyfire, which is interesting. It does, however, feel slower and more firm/dead compared to the springy and energetic Skyfire. The Peregrine security and fit is overall better and the upper feels higher quality, and the grip is truly top-notch, 10/10 on all surfaces, but the Skyfire is as versatile of a shoe and more fun/fast to run. The Peregrine is more of a tank and more durable, I’d trust it more in the wet as well, but the Skyfire would be my pick overall.

Skechers GOrun Speed TRL Hyper  (RTR Review)

Jacob: The Speed TRL is also a lightweight racing trail shoe, but much less capable on technical terrain than the Skyfire and I wouldn’t consider taking them to the mountains, as the lugs are small, fit a bit looser, and the grip fairly poor. Both shoes are good on road with a similar level of protection but the Speed TRL is notably lighter, though it’s also the lightest trail shoe I’ve ever run in, and the Skyfire is still quite light. I’d take the Speed TRL for more groomed terrain, rolling dirt style, but if the terrain gets technical, mountainous, or wet, I’d pick the Skyfire without question.

Topo Athletic Runventure 3 (RTR Review)

Jacob: Both shoes are nearly the same weight and include a flexible rock plate in the forefoot. The Runventure wins on fit for sure, being one of the most comfortable shoes I’ve ever worn (much wider toebox), but having great security overall. The Skyfire’s more precise fit is better on very technical terrain but less comfortable overall. Both shoes have good grip on a variety of terrain, but the Skyfire is vastly superior on ice/snow. The Runventure is zero drop and relatedly feels far less cushioned overall and doesn’t have the same bounce or forgiving feel of the Skyfire. The Runventure is also harsh and not fun on the road. 

The ride, versatility, and price of the Skyfire make it my choice for most runs and with the fit, certainly the choice for racing, but the high comfort and more connected to the ground feel of the Runventure is uniquely enjoyable on some runs, especially shorter distances, so I still run them when I want that fit and feel.

Nike Zoom Terra Kiger 6 (RTR Review)

Canice: The Kiger has a much wider toe box and even more ground feel while the Merrell MTL Skyfire offers more cushioning and a snugger fit. If you like one, there’s a good chance you’ll like the other. For my part I would take the MTL Skyfire on a longer run due to cushioning. 

Salomon Sense 4 Pro (RTR Review)

Canice: The Sense 4 Pro may be the King of “precise foot placement” shoes but it has a firm ride which I really enjoy. The Merrell MTL Skyfire is also a precise foot placement shoe with a softer more cushioned ride that you’ll come to appreciate over longer distances. Both are great shoes and if you’re running Salomon’s you’ll likely stay put but if you’re looking for another option you’ll want to give the Merrell MTL Skyfire’s a try.

I personally like both shoes and tested the Salomon Sense 4 Pro first. It felt great the moment I slipped them on and I love the balance of ground feel and cushioning. It's a very "precise" style of running shoe as it relates to foot placement while running and I tend to like this.

This was the first time I have worn a Merrell running shoe and was surprised how much I liked it. It really felt great and was a lot of fun to run in. Good ground feel too but they have a slightly more cushioned feel than Sense Pro 4 which I attribute to the spring within the foam, but the difference is very minor. I think someone is more likely to choose between the shoes based on fit. The outsoles are very different too.

If we add the Salomon Sense Ride 3 (RTR Review)  into the mix it would win the day on cushion. It picks up a bit of weight but definitely has a more cushioned feel. I also feel with the Sense Ride 3 that I can pound my way through trails and though I'm still careful with my foot placement, I feel less underfoot and thus let loose a bit more. 

Read reviewers' full run bios here
The product reviewed was provided at no cost. The opinions herein are the authors'.
Comments and Questions Welcome Below!
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Morgan said...

Thanks for another great review just curious if this is different to the MTL Cirrus that was released last year or is it rebranded?

Sam Winebaum said...

Hi Morgan, the Long Sky May be a closer replacement. Fire is 1oz lighter and it appears a different flavor of EVA, lighter. Outsole of Cirrus is MegaGrip as is Long Sky’s. This said Stack height of Fire and Cirrus are close. Sam, Editor

Anonymous said...

Thanks for the review everyone! Really looking forward to trying out these new Merrells (Long Sky as well). I did not notice any feedback regarding sizing. Some of the shoes lately have been all over the place with sizing (Salomon), so some comparisons would be welcomed. True to size, or suggest sizing up/down?

These reviews are helping to keep me sane during these difficult times. Very much appreciated!

Anonymous said...

Hi This is Canice. Sorry we did not mention the sizing. For my part I almost always wear a size 10 and the size 10 I tested fit perfect. Cheers,

Xavier said...

Basic EVA provides better cushioning and comfort than the optivibe in the sense 4 pro? This a little bizarre. I wonder how it compares to the optivibe in the ride 3 or accelerate?

Sam Winebaum said...

Hi Xavier,
I will let Canice comment on the comparison to Sense Pro 4 to Sky Fire midsole. I have run in the slightly more cushioned Long Sky version, the Sense Pro 4 and the Sense Ride 3. First while they say it is EVA it is pretty clearly a different flavor say compared to Energy Cell+. It is bouncier, softer, more dynamic for sure. Compared to Optivibe I find it a bit less dense with a bit more shock transmitted. I find thicker Optivibe such as in Ride and Balance duller more muted in feel than in lower profile Optivibe such as Accelerate and Sense Pro 4. Less is more with this midsole make up. I can say the Long Sky is very lively very well cushioned although as it has MegaGrip the firmer rubber outsole in the mix when run on say roads is more noticed. It terms of fit while fine the Ride has a superior more secure upper with Long Sky a bit baggy when pushed beyond the support of its stout gusseted tongue. Hope this helps.
Sam, Editor
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Anonymous said...

Hi Xavier,

This is Canice. I had the pleasure of testing both the Merrell Skyfire and the Salomon Sense 4 Pro. We don't really know what the compound of EVA used is so it's hard to classify it as "Basic" but the description of the material is very simplistic. With that said I personally like both shoes and tested the Salomon Sense 4 Pro first. It felt great the moment I slipped them on and I love the balance of ground feel and cushioning. It's a very "precise" style of running shoe as it relates to foot placement while running and I tend to like this.

This was the first time I have worn a Merrell running shoe and was surprised how much I liked it. It really felt great and was a lot of fun to run in. Good ground feel too but they have a slightly more cushioned feel which I attribute to the spring within the foam, but the difference is very minor. I think someone is more likely to choose between the shoes based on fit. The outsoles are very different too.

If we add the Salomon Ride 3 into the mix it would win the day on cushion. It picks up a bit of weight but definitely has a more cushioned feel. I also feel with the Sense Ride 3 that I can pound my way through trails and though I'm still careful with my foot placement, I feel less underfoot and thus let loose a bit more.