Salomon S Lab Sense Set Hydration Vest – Review

Salomon showed a new hydration vest design language last July when Kilian Jornet wore a prototype at the 2014 Hardrock 100. It looked like a very “skin fit” vest with integrated pockets that Kilian had fully stuffed for the race. Many were very interested to see what Salomon would actually bring to market (if anything).

In August the S Lab Sense and S Lab Sense Ultra vests were introduced at numerous outdoor product industry Expos (like the OR show in Salt Lake here in the US). The pictures of the vests and the general minimalist design seemed be taking this type of equipment along the “Sense” thought path where pieces are stripped down to the essentials yet remain highly functional and of high performance. I vowed to give these vests a try once they were available.

In January 2015 I received both a S Lab Sense Set and a S Lab Sense Ultra Set and began using them straight away.  After fussing with the sizing I finally settled in on XS/S for my 5’7″ frame at 125 lbs and about 7% body fat. I give all of this sizing info because the vest is a “skin fit” product and therefore “similarly” sized individuals may need to up-size or down-size, depending on specific body characteristics. In the past I have been a M/L in the previous Salomon vests but in the S Lab Sense Set line the M/L is way too large for me (other reviewers of the Sense Set vest have made the same observation). So Salomon have clearly changed the sizing of their vests for 2015, at least for the Sense line. I will note also that the previous generations of Salomon vests have been the only piece that I did not wear a S, so I think the sizing designations in the past have been not consistent with Salomon’s other products. Perhaps they have now “fixed” that issue… time will tell.


As mentioned above, the design of this vest includes a “skin fit” base and as such the vest sits almost as a part of your torso, rather than as many other such vests that feel like you are wearing them. This feeling of the vest being an extension of your body was very much the way the previous generations of Salomon vests have felt, however the Sense line takes this up another whole level. With the Sense Set vest the entire functionality of the vest is integrated, meaning that the pockets are no longer just appendages on a base structure but rather the pockets are an integral part of the structure. This design approach leads to some new ways that one must use the vest for best performance as will be discussed later.

The entire base structure is constructed of a Cocona 3D mesh fabric similar to the Cocona 2D mesh fabrics used in the Sense clothing line. The Cocona-based fabric is claimed to be highly breathable, quick drying, and comfortable against the skin. I agree on all counts. The vest comes with two 500 ml soft flasks and a safety whistle (which can be removed).

Salomon S lab Sense vest front

Salomon S Lab Sense Set hydration vest front. The vest comes with two 500 ml soft flasks and a whistle (which can be removed). Note that the entire base structure of the vest is a highly breathable mesh material. There are two upper pockets- one open with an elasticized edge, one zippered- and two lower pockets with elasticized edges to keep the contents secure. Two soft, slightly elasticized, chest straps connect using plastic hooks on fabric rings- very comfortable.

The front portion includes two pockets for the soft flasks (or other stuff if one is using handhelds), two upper pockets- one open with an elasticized edge, one zippered- and two lower pockets with elasticized edges to keep the contents secure. Two soft, slightly elasticized, sternum straps secure the vest in place and connect using plastic hooks on fabric rings allowing for individual adjustments. I find the fit to be very comfortable.

The back is entirely vented right down to the waist of the vest and there are two zippered side pockets made of stretch mesh that are intended for stowage of additional clothing (jackets, gloves, buffs, etc.), headlamps and other electronic hardware, and fuel (gels, bars, whatever). The side pockets are also sufficiently large to hold the 237 ml (8 oz) soft flasks. This allows for carrying up to a total of about 1.5 l of fluids. The side pocket zippers are conveniently placed and quite accessible even for an ageing, less flexible runner like me. No “Houdini” moves are required to open the zippers on this vest- something I cannot say for a lot of other vests.

Salomon S Lab Sense vest back

Salomon S Lab Sense Set hydration vest showing the enitriely vented back structure and the zippered side pockets extending into the back region. These vented pockets can hold quite a bit of “stuff” including additional fluids.

The vest comes in two variants, the Sense and the Sense Ultra. The vest variants are identical except that the Sense Ultra adds two additional pockets in the rear- one along the lower portion of the back and one on the upper portion of the back. These additional pockets significantly increase the total carrying capacity from 1 liter (Sense) to 3 liters (Sense Ultra). These volumes are in addition to the 1 liter carrying capacity of the two included 500 ml soft flasks. The Sense vest weighs 90 (yes, 90) grams and the Sense Ultra vest weights 110 grams. Incredibly light!

Salomon S Lab Sense ultra vest back 2

Salomon S Lab Sense Ultra Set hydration vest back showing two additional pockets at the rear, one across the lower back and one in the upper back region- both overlaying the underlying mesh of an otherwise Sense vest. This is the style of Sense vest that Kilian used at the 2014 Hardrock 100.

All of the vest edges are soft and do not chafe. The design also allows for use of this vest without a shirt, jersey, or singlet. I found the vest to be comfortable shirtless although wearing it this way will require application of sunscreen throughout the torso as the Cocona mesh fabric provides little if any sun protection. I prefer wearing a shirt anyway, having a “fair” complexion and a higher than average affinity to sun-induced skin issues. Being in my 60th year, I am now seeing many friends and acquaintances in my age group suffering from various forms of skin cancer and I will suggest that you take prevention seriously if have not already. The “chickens will come home to roost” and it will not be pleasant when they do.


As I mentioned earlier Salomon have changed their sizing for the Sense vest so be aware that you are likely to need a smaller vest if you have used Salomon’s other vests in the past. This is a bit frustrating for those of us who expected uniformity but in the end I have found the XS/S size to be a very good fit.

The overall fit of the vest is excellent, very comfortable, and seamless. The positioning of the pockets and flasks does not interfere in any way with running, including steep downhills where many vests seem to begin to interfere with swinging arms, at least in my experience.

When the 500 ml soft flasks are fully loaded the sternum straps will be adjusted for a firm fit but as the flasks are emptied one must begin to cinch up the straps to ensure a proper fit. This is because the flask pockets are an integral part of the vest structure- they are not just appendages. So as the flasks deflate the vest needs to be tightened. This is easily done on the run with the two sternum straps and I have found the performance to be excellent- the flasks stay close to the body and as a result the movement amplitude (and the associated momentum) is minimized.


I have now been regularly using this vest for over 5 months and for about 600 of the 1500 running miles in this period I have been wearing the Sense vest and for about 200 miles I have been wearing the Sense Ultra vest. Both vests have performed at the highest level of comfort and utility, although, for my running, I find the extra pockets on the Sense Ultra vest to be more than I need, even for solo runs in excess of 30 miles (50 km).

For a typical 20 mile (30 km) mountain trail run I will use the Sense vest and load it with the two 500 ml soft flasks (and depending on the weather/temperature, two 237 ml soft flasks in the side zippered pockets), an S Lab Light jacket in one side zippered pocket and a long sleeved shirt, gloves and a warm hat in the other one along with two bars ( about 200 cals each), one in each side pocket. In the upper front pockets I have permanently placed a lip balm, a “travel size” Body Glide, and a Salomon buff . In the lower front pockets I will put gels (4 or more) and a PB&J sandwich. If the weather looks wet or cold up high I will wear the Salomon S Lab Hybrid Jacket around my waist. I have been on 35 mile solo runs with this set-up and run into some challenging weather and had all that I need- all from a 90 gram, ultra-lightweight vest- cool! The vest is consistently comfortable, independent of the degree of loading and there is essentially no movement of the contents when properly adjusted. Some reviewers have indicated that the sternum straps have vibrated loose- I think that this is the result of the deflating soft flasks, and as mentioned above one needs to tighten-up the straps as the fluids are dispensed. I have had no issue with the sternum straps loosening on their own.

I have found that the Sense vest is sufficient for all of my needs as a solo mountain trail runner up to about 35 miles (or 50 miles with a water source along the way). The extra rear pockets on the Sense Ultra vest, although adding substantially more cargo volume, do not seem to be needed, at least for me. I find extra pockets and cargo volume just encourages one to carry more stuff, often stuff that you really will rarely, if ever need. The Sense Ultra vest also does not breath as well as the Sense vest since the entire back mesh area is covered up by the thin 3D mesh fabric of the pockets. This could be an issue in hotter summer running and racing.

As far as racing, the Sense vest is clearly all that one will need as the aid stations will more than provide what re-stocking you might need. I will be racing in the Sense vest this season and will report back with my experience after a 100 km high mountain, big vertical race in couple of weeks.

Some users might have a period of adjustment to this vest because it essentially has no rigid structure. It becomes a part of your body and behaves as such. If you like physical structure in a vest this may not be the one for you, but I find this design to be a great option and a light one at that.


The Sense vest comes in three colors- white (shown above), black, and red. The Sense Ultra comes in two colors- white (shown above) and black. Curiously, the white Sense Ultra is not available in the US. This is unfortunate because the white colorway is so much more visible in typical mountain conditions (except for snowfields) and if you ever need to be found, the black vest will likely be a liability. The Sense vest in red is also a good choice for visibility.


The S Lab Sense vest is $120US and the S lab Sense Ultra vest is $130US. These are competitive prices since they include the two 500 ml soft flasks. But you are also buying a super-lightweight, body-fit vest that is very efficiently packed and exceptionally comfortable.

Bottom Line

The Salomon S Lab Sense hydration vest is a super-lightweight, high quality, optimized volume, and exceptionally comfortable hydration vest option for mountain trail runners and racers. Highly recommended.

Salomon S Lab X-Series – Final Update

With over 750 miles (1200 km) of very comfortable trail running, I have now taken a first pair of the S Lab X-Series “road” shoes from box to bin. These miles have been almost exclusively in rocky and rocky technical trail situations including scree, scrambles, water crossings (including rivers), medium mud, snowfields, and precipitous knife-edges. The shoes are still very runnable but they have lost a bit of forefoot cushioning and, in an effort to be proactive about shoe wear-out rather than (regretfully) reactive to some sort of foot issue, I have taken this first pair off-line and started rotating two new pairs. I could continue running in these on shorter runs but I will probably use them for hiking through the summer. Suffice it to say that the X-Series has more than lived up to initial impressions and continues to be a great performer on just about any trail here in the Northern Rocky Mountains.


Salomon S Lab X-Series after 760 miles (1225 km) showing very little wear on the uppers and insoles.


These shoes have about 760 miles (1225 km) so at US$160/pair that gives a wear value of about US$0.21/mile (US$0.125/km). This is about the same calculated cost per mile as that experienced with the Sense 3 Ultra. 750+ miles (1200+ km) is very good wear in my experience even at the $160 price point.


The X-Series upper is constructed of three primary materials: a thin Lycra in the forefoot back to about the midfoot, a very thin mesh on the outside midfoot area, and a beefy nylon mesh for the remainder around the heel, etc. I initially had concerns about the durability of the Lycra and thin mesh materials, as Salomon in the past have used materials in the S Lab Sense line that did not wear well. Additionally, Salomon markets the X-Series as a “road” shoe with crossover capability to “City Trails” (whatever that means). The wear characteristics of this shoe in the rocky and rocky technical trails that I run was a concern as it relates to durability of the upper. Even after this significant mileage on rocky and rocky technical trails there is no sign of excessive wear (or wear at all) in any of the upper materials with the exception of the tips of the heel counter inside surface.


Image of the upper Lycra forefoot region showing no evidence of wear after 760 miles (1225 km). The Lycra material is clearly very durable in rocky trail use.


Similarly, the inside forefoot Lycra region also shows no wear.

The heel counter inside surface is the only place, other than the midsole cushioning, in the entire shoe that is showing any kind of wear-out. These wear-through spots do not affect the fit or function of the shoe at this point, but continued degradation will likely become bothersome.


The inside heel counter surface materials are starting to show wear and have developed holes.

The polymer-fabric overlays/lacing structure exhibit no wear and continue to perform as when new. The overlay fabric/ lacing structure materials are very tough as they experience a lot of strain and abrasion, yet, other than color fade, look new.

The “rocker” geometry has held up well and has, in fact, become more pronounced. I find that I very much like the “rocker” and suspect that this geometry may play a significant role in the high comfort level of the X-Series.


The Salomon S Lab X-Series “rocker” after 760 miles (1225 km). The “rocker” is a bit more pronounced after use.

Salomon X series compared to Sense 4

Compare the image above to the “out of the box” rocker of the X-Series and Sense 4 in this image.



After a few bouts with foot bruising I have committed to retiring a shoe before a worn-out EVA layer leads to some sort of acute or chronic foot issue. I have experienced both and solved the issue with shoe replacement. In the X-Series I am perhaps retiring this pair a bit sooner than I would have in the past, but I am trying to navigate a balance between wear-out and insufficient cushioning. I am erring on the more cushioning side of that balance going forward. A runner with a “tougher” foot might get another couple hundred miles out of these shoes.


Perhaps the most remarkable circumstance with the X-Series is how durable the outsole is. I am a significant supinator and therefore typically see excessive wear on the outside edge of the outsole, particularly at the heel (see my other reviews and updates of the S Lab Sense variants for examples of this type of wear). The X-Series shows almost no wear across the entire surface and clearly the outside heel area is not differentially worn relative to the rest of the outsole. It is hard to believe when looking over the outsole that these shoes have seen 760 miles (1225 km) of use on rocky and rocky technical trails, including scree, scrambles, and many water crossings.


The outsole of the Salomon S Lab X-Series after 760 miles (1225 km) showing very little wear and no preferential wear at the outside outsole edge and, particularly, the outside heel area. This is the first S Lab shoe that I have used that has been this durable given my substantial supination.


The Salomon S Lab X-Series is the most comfortable trail shoe I have ever used, and my use includes many of the Hoka, Innov8, and Altra offerings. I will note here that I also had initial concerns with how “hot” the X-Series would run as Lycra is well known for not being very breathable. Having run a few times in air temperatures exceeding 85 F (30 C) where surface temperatures were in excess of 100 F (38 C) I can report that the shoes actually run quite cool and certainly on par or better than the Sense. Also the proprioception of the X-Series is outstanding and leads to substantial confidence while running in technical and challenging terrain as well as increased speeds on descents.

How Salomon accomplished all of this with what is billed as a “road” or “hybrid” road/trail shoe I am not certain. I will offer that the combination of a larger outsole area, larger outsole contact area, the dual density EVA construction, (apparently) just enough additional midsole thickness, and light materials has resulted in a very different shoe than the S Lab Sense- one that not only performs in the mountains but also does so with a comfort level much greater than the Sense, particularly on long runs/races. It seems also that there may be some sort of midfoot construction detail that leads to a higher comfort level as one fatigues and begins to transition from a high proportion of forefoot strike to increasing amounts of midfoot and heel striking. All of this is conjecture but the proof is in the taste of the pudding…. and this is very good pudding!

Bottom Line

Salomon have (unexpectedly, since the X-Series is supposedly a “road”/”hybrid” shoe) produced a high performance, light-weight trail shoe that provides a high level of long run comfort, superior trail feel, high durability, and all-around performance on mountain terrain. This is a shoe that trail runners should consider even though Salomon bill it as a “road” or “hybrid” road/trail shoe. Highly recommended.

I will be using the S Lab X-Series exclusively for training and racing this season including two 100 km high mountain/large vert races, a four day mountain stage race (with obscene vert), and a high mountain 50 miler. Looking forward to where Salomon takes the X-Series for SS2016.



Salomon S Lab X-Series Update – a continuing great performer

I have reviewed the Salomon S Lab X-Series “road” shoe previously with initial impressions here and, after some use on varied terrain, in comparison to the S Lab Sense 4 Ultra trail shoe here. Initial and continued use of the S Lab X-series “road” shoe revealed that it not only performs very well on roads but also on the trails, at least on the trails here in the Northern Rocky Mountains of the US.  This post is an update after considerable additional use of the X-Series on a wide variety of terrain.

I now have about 700 km (435 miles) on a first pair of X-Series and have recently introduced a second pair of X-Series in rotation. A third pair is being set aside for races. As should be obvious, I have committed entirely to the use of the X-Series for all trail and ultra-trail races and associated training going forward in 2015. When compared to the Sense 4 Ultra, the X-Series has sufficient trail prowess to be a good choice for all but the most demanding of technical trails (think Trofeo as an example of where you might choose the Sense 4 over the X-Series). At the same time the X-Series offers significantly increased comfort over the Sense 4, particularly on long (>30 km) runs. The following is a summary of my experience using the X-Series “road” shoe on trails.


As expected from a “road”- trail hybrid shoe, performance on flatter and buffed trails is outstanding. But, as has been indicated in previous reviews, the X-Series exhibits surprising performance on trails in general and specifically on rocky and “technical” sections, both on the ups and the downs. Based on the Salomon literature and introduction material, the X-Series was not designed as an all-around trail shoe, yet my experience is that it is and it is a great performer.

The X-Series has continued to shine on anything that the Rockies can dole out with the exception of deep mud where the larger platform and ground contact area of the X-Series lead to a fair bit of “float” when compared to the Sense 4 and FellCross 3*. I have been able to run with confidence on all of the trails that I have run in the Sense line in the past 3 years and notice very little if any difference in performance. What is different is comfort, where the X-Series is much superior, at least on my 60 year old feet. It is not clear why the X-Series is so comfortable on longer runs, although I suspect that the midsole design in the midfoot is playing a large role. Overall from a performance perspective, I can highly recommend the X-Series as an outstanding trail performer and as a shoe quite ideally suited to ultra trail events.


As noted previously, the X-Series utilizes some materials that have not been seen on Salomon shoes in the past- specifically the Lycra forefoot upper and the super-thin mesh on the outside mid-foot upper. In addition the outsole wear layer is glued onto the midsole material in segments which is a design approach that Salomon have had issues with in the past. These are the areas of the shoe that I have been keeping an eye on.

As of this juncture and with about 700 km (435 miles) of use, it is apparent that these “suspect” areas and the shoe in general is holding up exceedingly well. There is no evidence of excessive wear on any section as can be clearly seen in the following images.



Salomon S Lab X-Series after approximately 700 km (435 miles) of use. No evidence of excessive wear anywhere on the upper, the outsole, or in the construction.

A closer look at the outsole shows that the wear layer is quite durable, more so than what I have experienced with the Sense line of shoes over the past three years. As a supinator I typically see increased wear on the outside of the mid-forefoot and on the outside of the heel area. As can be seen in the image below neither of these areas show an increased wear relative to the rest of the outsole. I am not certain as to why this might be but the increased footprint and increased area of contact may be playing a role. The geometry of the shoe design (including increases in footprint, area of contact, the “rocker” element, and the details of the midsole structure and composition) is likely the reason for such even wear of the outsole.


Outsole of the X-Series after 700 km (435 miles) of trail running including about 30% rocky technical, 60% buffed singletrack, and 10% road use.


I have experienced no significant issues with use of the shoes- the fit has remained excellent, the stability and traction have not diminished, and the materials are holding up well. I have, however had one incident that is making me focus a bit more on the applicability of this shoe in truly technical terrain.

Although this incident could have been entirely stochastic, I have never had such a thing occur in over 35 years of running. While on a long run through some very technical terrain I noticed that there seemed to be a small stone in the shoe. After a while I stopped and took the shoe off and emptied out any debris that had collected inside the shoe. Some small stone chards fell out. I put the shoe back on and continued running however the stone I felt previously seemed to still be in there. So I stopped again and emptied the shoe, something else fell out and I thought that would be it. But after continuing I still felt the stone. So I took the shoe off again and felt very carefully and realized that there was a stone under the insole, something that has never happened to me. I removed the insole and finally found the culprit- it was a small sharp stone that had penetrated through the exposed midsole (EVA) material, through the ProFeel rock plate, and into the interior of the shoe. The following images show this.


Looking into the shoe with the insole removed showing the puncture from a sharp stone.


Image of the outsole, the sharp stone, and the place where the sharp stone penetrated the outsole area (I saved the stone after removing it).


The insole removed where the penetration can be seen in the lower section of the trailing end of the forefoot.


The opposite side of the insole showing the penetration point.


The penetration point on the underside of the insole and the offending sharp stone.

It took quite an effort to remove the sharp stone from the shoe. I was never able to get it back in either. I expect that this was likely a chance event- the right sharp stone in the right orientation, the right location on the sole, and the right placement of the shoe on the stone. But I will be keeping a peeled eye towards any further events- both with or without puncture. It still seems unusual that such a stone would penetrate the ProFeel film, but that seems to have clearly happened.

Bottom Line

The Salomon S Lab X-Series hybrid “road”/trail shoe is an outstanding trail shoe that is very light, has excellent fit, durable upper and outsole, and is exceedingly comfortable on long (>30km) runs. The shoe handles anything from buffed singletrack to highly technical rocky terrain to wet rocks/roots and medium mud. Deep mud conditions will be challenging in this shoe (as they are in the Sense 4 Ultra) so if deep mud is common in your running there are better options.

I can highly recommend this shoe for both training and racing trail and ultra-trail events.


*Generally, US trails do not include wet grass conditions as most trails are developed, are substantially dirt and rock, and it is not encouraged to deviate from the established trail. Fell running on the other hand is very much the opposite. I have not tested the X-Series in “Fell” conditions so all comments here exclude application to Fell running.


Salomon S Lab X-Series vs. Salomon S Lab Sense 4 Ultra – 911 vs. GT3

In a recent review of the Salomon S lab X-Series “road” shoe I hinted that, based on limited trail miles, it seemed that the X-Series might prove to more of a trail shoe than expected. Well, now, after a little less than 200 miles (300 km), I can affirmatively attest to the trail-worthiness of the X-Series. In fact I will go so far as to say that this shoe is hitting an optimum mix of characteristics for all but the most gnarliest of trails- even though Salomon classes it as a “road” shoe with some trail capability.

So, I have tested the X-Series against Salomon’s top-of-the-line trail shoe, the S Lab Sense 4 Ultra. This comparison test has been conducted on all of the same trails, conditions, and terrain. The primary trails are mountainous buffed to mid-technical, the terrain has included steep (>60% grade) trail, off trail talus, slickrock, bog, stream, and river crossings, and the conditions have included snowfields, clay mud, ice, and sand. A good variety that includes just about everything that one might encounter in the Rockies with the exception of the “moondust” that typically develops later in the summer on some trails. The following is a summary of the differences, similarities, and superiorities between these two shoes.

In the end the two shoes compared in a way that a 911 might be compared to a GT3– both models are very high performance options, but one is much more “edgy” and tuned to a specific purpose whereas the other is a more widely usable and comfortable design with numerous advantages.

Note: 23 April 2015- I have posted an update on the performance of the S Lab X-Series at about 700 km (435 miles) of use here.


The S Lab X-Series shoe was announced last summer in Europe and the US and came as a bit of a surprise since Salomon have not ever played in the “road” shoe market but have, rather, focused on the trail shoe market. When this “road” shoe was introduced many cast a wary eye given Salomon’s lack of experience in this area. However, usually when Salomon does something they do it right and “different” than the competitors. And this holds true for the X-Series.

Salomon X series overall

Salomon S Lab X-Series

The S Lab Sense 4 Ultra is an evolutionary derivative of the  original Sense line brought out in 2012. As can be gleaned from the name of the shoe, Salomon are on the 4th generation of the Sense. In 2012 the shoe introduced super light weight, high traction, incredible proprioception, ultra-light ProFeel carbon fiber rock plate, some unique materials, and, most importantly, Endofit construction to the trail running world. The EndoFit construction has been universally acknowledged as a superior approach to fit and feel. The progression of the models since have fixed performance and durability issues primarily with added traction (more and deeper lugs) and new, more durable, materials and constructions. Such is the same with the latest iteration in the Sense 4. This shoe is the flagship of the Salomon trail running offerings but the model has become a bit “long in the tooth” since there have been no real advancements beyond those first introduced in 2012. It is expected that Salomon will disrupt the trail running market sometime soon with an all-new model, perhaps with a dose of the carbon technology that they have been applying to the cross country ski boot and mountaineering boot markets.


Salomon S Lab Sense 4 Ultra



The X-Series and Sense 4 both employ many of the same construction elements and materials- EndoFit, ProFeel film, SensiFit, and ContraGrip outsole. The differences lie in some of the materials in the upper, the amount of dual-density EVA incorporated, the design and attachment of the outsole wear layer, and the geometry of the shoe itself.

The X-Series offers a wider forefoot (about 3 mm on my size 7.5US, 40 2/3 EU) and a wider, squarer toebox. The heel is also wider by about 5 mm on these size 7.5US.

Salomon X series comparison forefoot

Toebox and forefoot area of S Lab Sense 4 Ultra (left) and S Lab X-Series (right) showing the wider, squarer toebox and a 3 mm wider forefoot dimension in the X-Series (size 7.5 US (40 2/3 EU)). The heel of the X-Series is also wider- by about 5 mm.

Perhaps a more significant difference is the midsole stack where the X-Series has a 19 mm heel/11 mm forefoot and the Sense 4 has 13 mm heel/9 mm forefoot stack. Both models use “dual-density” EVA where a cushier EVA can be placed where needed (I assume that the lower density, softer, EVA is in the forefoot and heel). The overall stack height (including the outsole) for the X-Series is 23 mm heel/15 mm forefoot giving an 8 mm drop. The Sense 4 adheres to the “low drop” Sense design ethos with a total stack height of 19 mm heel/ 15 mm forefoot and a 4 mm drop.

The outsole design is quite different as expected since the X-Series is intended for roads and “city trails” (whatever that means). The Sense 4 continues with the minimalist chevron array that has proven to provide outstanding performance in everything but ice and, to some extent, water crossings on submerged rocks. The X-Series outsole has a much larger surface area of contact but still with significant, deep lugs in strategic areas. The X-Series also has a segmented outsole wear layer that is glued on whereas the Sense 4 outsole wear layer is one piece. Salomon had durability issues in the original Sense model with such segmented wear layers coming off due to failure of the glue and the associated very long exposed glue-line. Hopefully they have since figured out a reliable and durable way to glue these segments.

Salomon X series outsole

Salomon S lab Sense 4 outsole

S Lab X-Series outsole (top) and Sense 4 outsole (bottom) showing large difference in traction design between the two models.

The X-Series also has a deep cutout extending from the middle of the outsole rearward into the heel area. It is not clear what this design feature is for but it may provide additional longitudinal stiffness through the middle of the outsole. Upon examination the X-Series is much stiffer longitudinally in this area than the Sense 4, although the forefoot stiffness is similar between the two models.

The X-series employs a significant “rocker” geometry, similar to that in the Hoka line of shoes. The Sense 4 retains the low, flat profile of past Sense models.

Salomon X series compared to Sense 4

Salomon S Lab X-Series (upper) and Salomon S Lab Sense 4 Ultra (lower) showing the substantial “rocker” geometry incorporated in the X-Series when compared to the Sense 4 Ultra.


The heel cups are similar but the ankle cups are different. The X-series has a symmetric ankle cup whereas the Sense 4 has an asymmetric set-up. I have felt no difference between the two while running, so it is not clear what the higher inner ankle cup does on the Sense 4 other than perhaps protecting a bit more in rocky conditions and from opposite side heel scuffing.

Salomon S Lab X-series back comparison

Rear view of the Salomon S Lab Sense 4 Ultra (left) and the Salomon S Lab X-Series (right) showing similar heel support structure but very different ankle cup configurations.


Salomon X Series ankle cup comparison

Ankle cup comparison showing Salomon S lab Sense 4 Ultra (top) and Salomon S Lab X-Series bottom. The Sense 4 has an asymmetrical cup whereas the X-Series is symmetric. The Sense 4 also has much more rear roll-over of the padding.


The upper materials are quite different where the Sense 4 utilizes the same (or similar) 3D fine mesh fabric throughout the upper with the heel wrapped in a tough solid polymer as seen in previous Sense models. The X-series uses primarily three different materials in the upper- a “barely there” mesh on the outside panel for ventilation, lightweight Lycra through the toe and forefoot region, and a beefier nylon fabric around the heel and throughout the inside are area up to the forefoot.

Salomon X Series side veiw

Salomon X series viewed from above

View from above of the Salomon S Lab X-Series showing a toebox and forefoot that is wider than that in the Sense 4 Ultra.



The s lab sense 4 uses the same (or similar) 3D mesh material as found in previous Sense models for the entire upper with the exception of the hard solid polymer around the heel.



View from above of the Salomon S Lab Sense 4 Ultra showing the slim and fast profile that is a fundamental part of the Sense line.

The polymer overlays look similar but they are actually very different. They both have the signature “zig-zag” side features but the X-Series toe area is much more pliable than the Sense 4. The Sense 4 overlay is much more structural and therefore the Sense 4 provides much more protection for toes than the X-Series. Both models have similar toe bumpers however as this is the most likely place that one will stub a toe.


The two models have very similar weights. The S Lab X-Series shoe is quoted as weighing in at 218 gms (7.7 oz) for a size 9 (US). My size 7.5 (US) (40 2/3 (EU)) tipped the scales at 215 gms (a little less than 7.6 oz). That is lighter than the quoted 238 gm for a size 9 (US) in the Sense 4 and the actual measurement of my Sense 4 Ultras in size 7.5 (US) at 227 gms.


The X-Series is $160 US and the Sense 4 Ultra is $170 US. Both are expensive shoes but if they last as long as other S Lab shoes I have used, the “pennies per mile” metric should make these shoes a reasonable offering from a price perspective.


RED! Salomon have simplified the graphics and the all-red X-Series are quite distinctive. No other colors are available in either model.

Running Performance Comparison

As outlined above I have tested these shoes on the same trails, conditions, and terrain. They have both seen about 200 miles (300 km) of use on buffed to mid-technical trails and terrain varying from steep (>60% grade) trail, off trail talus, slickrock, bog, stream, and river crossings. The conditions during testing have included snowfields, clay mud, ice, and sand. This is a variety that includes just about everything that one might encounter in the Rockies with the exception of the “moondust” that typically develops later in the summer on some trails.

General Running Characteristics

When comparing these two shoes the primary difference one will note at the outset is the cushioning and the “rocker” geometry of the X-Series. This makes the X-Series stand apart from the Sense 4 not only on the road but very much so on the trail. Proprioception is better in the Sense 4 but the X-Series has very good trail feel albeit with a bit of dampening.

The cushier ride of the X-Series is welcome, particularly to those used to the direct, somewhat hard ride of the Sense. While the Sense is likely to comparatively increase stride efficiency this comes at a cost of comfort and durability as it concerns ones feet. The X-Series provides a nice compromise between the “hardcore” trail feel of the Sense and the disconnected trail feel of a maximal shoe like a Hoka Stinson.

The X-Series also has a slightly larger total area outsole and much larger surface area of contact. One will feel this immediately as well and, just as such larger area outsoles do with the Hoka line, there is a perceptual “smoothing” of rocky trails in comparison to the Sense. Although I have yet to be on highly technical, fast running trails yet, I have not noticed a significant decrease in control between the Sense and the X-Series. The X-Series feels just as nimble as the Sense on typical buffed to mid-technical trails.

The larger, squarer toebox of the X-series is noticeable and in certain situations one can feel a bit more movement in the forefoot, particularly on steep downhills. I have run a couple of 3 mile ( 5 km) continuous steep (>15%) downhills in both models and found similar pace and feel except in the steepest (>50% grade) of areas where the X-Series begins to break loose where the Sense does not. The EndoFit is obviously doing a great job of helping one to maintain control in such challenging conditions and the ProFeel rockplate is doing an outstanding job protecting against sharp rocks.

In a couple of long (30+ km) runs on the same course the X-Series proved to be a very comfortable option when compared to the Sense 4. My feet were ready for some relief at about 32 km in the Sense 4, whereas, in the X-Series, I was looking forward to continuing on. That’s a big difference and one that will play a major role in a 50-100 km race.

Performance in Water, on Snow, and on Ice

One concern I had initially was that the Lycra upper of the X-Series would not drain after a water crossing as well as the 3D mesh of the Sense does. Not so, and, in fact, the X-Series is draining better in my experience.

More importantly, the X-Series performs much better on wet and/or slippery rocks. I found very good traction in stream crossings with the X-Series where the Sense would be somewhat unstable, particularly if any algae was present. The X-Series crosses rock-strewn streams with confidence and stability. This is most likely due to the simple physics of increased surface area for the ContraGrip when compared to the Sense- a lowered net shear stress for the X-Series allowing for significantly increased traction. I will update on performance in this condition once the summer algae thickens up on the submerged rocks.

A similar experience is found on snow and ice- the X-Series just plain outperforms the Sense on snowfields and ice. First, the increased traction helps establish control. Second, glissading is much smoother and controllable with X-Series as once static friction is overcome and gliding begins the larger surface area and less aggressive lugs allow for a “ski feel” and the associated control. Being a cross country skier helps but I was able to traverse a 200 m snowfield in one controllable glissade whereas in the Sense this same snowfield required three starts and stops due to “dig-ins” and lack of control. The same has been my experience on ice- the X-Series is much more stable on ice. Of course the Sense is particularly bad on ice but, with the X-Series, I was able to safely cross numerous “luge runs” of glare ice  that routinely  develop in the woods as winter fades and spring arrives. I would not even try to do these crossings with the Sense.

One outstanding question is how hot will the Lycra be; the material is thin and drains well but Lycra is not a particularly cool fabric in hot weather. Durability of the Lycra in abrasive conditions is another concern- time will tell.

Off Trail and Performance in Mud

I have taken the X-Series across some significant talus fields at running pace both up and down and have found very good performance, and, in some cases, better performance than the Sense which is already an outstanding performer on talus. Once again the source of the superior performance of the X-Series on talus is the increased dry traction when needing to make a big move on the talus field during descents. The larger surface area provides just that little bit more of a direction-changing force needed when heading directly for a large boulder or drop-off.

When crossing bogs I feel no difference between the models and the X-Series performs admirably right through the best muck and bramble that Idaho can offer. In pure mud, I was concerned that the big cutout in the outsole would just serve as a reservoir for mud and a large area for attachment of additional mud, particularly in clay-based mud. This did not happen and I find that the X-Series actually accumulates less mud than the Sense; not sure why. But as far as traction in pure mud on trail, the Sense 4 is superior; the widely spaced and aggressive lugs on the Sense 4 do a good job of piercing through the mud and hanging on to whatever grip is available whereas the X-Series tends to float a bit until one engages the outer, deep lugs. In practice this means that you will slide around a lot more in the X-series on mud so if you are regularly running in mud, the X-series would not be a good choice. My experience here in the Northern Rockies is that on the rare occasions when we do have significant sections of mud nothing seems to work very well (read the accounts, for example, of the 2014 Bear 100).

Concluding Comments

What I have found with the S Lab X-Series “road” shoe from Salomon is quite unexpected from what I thought the shoe would be. I expected a road shoe that could be used on buffed trails. The X-Series turns out to be an excellent, very nimble trail performer in a broad range of conditions even rivaling the outstanding performance of the Sense 4 in certain cases. This all comes with a nice dose of cushioning. Although I look forward to seeing how durable the outsole and upper is in long term use on muntainous trail conditions, it seems that Salomon may have hit an optimal mix of performance and comfort with the X-Series.

The S Lab Sense 4 Ultra continues with the outstanding, high performance, and “edgy” character of the Sense line giving unequaled proprioception and control on high speed trail downhills and all around performance for mountain running. The ride is “direct” and hard but efficient. It is also marginally comfortable at distances greater than about 50 km.

Bottom Line

Just as the 911 offers a nice mix of performance and comfort when compared to the “edgy’, stark, but super fast and controllable GT3, the S Lab X-Series does the same when compared to the S Lab Sense 4 Ultra. The Sense 4, like the GT3, has capabilities second to none in certain conditions, but this performance comes at a cost- long distance comfort. The X-Series offers a little less performance (and “egdy-ness”) in some cases and better performance in others, but a lot more comfort for the longer races and runs.

I’m going with the X-Series for my trail running going forward this season. And I am not the only one- Max King ran the LA Marthon in 2:17:30 in the X-Series, Justin Houck just won the 2015 Gorge Waterfalls 100k Montrail Cup Race, and Ellie Greenwood ran the Vancouver Marathon in 2:47 in the X-Series. Quite the versatile shoe!

I’ll keep you updated.

Embrace Your Conditions!

While studying at Oxford in the early 80’s I wanted to absorb a “full” experience during this English sojourn. So in addition to saturating into the academic life among the colleges, I sought out new athletic opportunities as well. After being “consoled out” of my college’s intramural rugby team by the coach (he feared for the life of a scrawny, 122 lb, American oblivious to the reality of rugby as a sport), I took to a lightweight crew and stumbled into an active Fell running community. The crew experience was great and provided much insight into the truly team nature of this sport (both on and off the water) and the rather elaborate traditions, but the Fell running proved to be much more of an experience for me.

My memories of the Fells were sparked when I saw the recently released African Attachment/Salomon video with Rickey Gates and a number of Fell running greats on Fell running in the Lake District:

The robust group of runners that I had the pleasure to run with for a couple of seasons made a significant impact not only on my running but also (and in a much greater way) on my perspective as it relates to truly experiencing a place.

The mantra of the group was: “Embrace your conditions!”. Independent of how raw and unwelcoming the conditions were (and “raw” and “unwelcoming” are mild versions of what one might regularly encounter in the Fells) we celebrated the visceral and intimate experience that would naturally materialize when one did not let the conditions become a barrier. It was new territory for me as previously I would typically limit a run or not run at all unless the conditions were at least palatable. But with the encouragement and peer pressure from the group I came to actually prefer the difficult conditions that were not infrequent in the Oxford area, the Cotswolds, the Peak District, and the Lake District where we ran.

This mindset and mantra has ever since informed how I try to approach life’s experiences- whatever the endeavor be it athletic, professional, or what have you. Rather than attempting to alter or otherwise modify the conditions that face one, this approach embraces what exists and challenges one to figure out how to make a way through, cover the ground, and finish- whether a run, a race, a project, or a relationship. This is not easy to do as we often fall into the mindset of “what could or should be” rather than making keen observations of “what is” and figuring out a way to go forward. Also, the forces at work can seem insurmountable- and many times they are. But this should not deter one from maintaining the mindset and moving forward, constantly re-evaluating what is the best path given the current circumstance. For me, it took many years before this approach became the default, but once in place what had previously appeared as insurmountable barriers became opportunities for optimization, challenges rather than burdens, and, in the end very valuable experiences.

So the next time you face a training run with a mix of rain and snow, deep muddy conditions, a driving wind, and low visibility think about “embracing your conditions”- you just might have a valuable experience upon which to draw in your next race when the inevitable unexpected happens.


Salomon SpikeCross Sense

With a low snow winter, lots of sunshine, warm temperatures, and an injured shoulder, running has materialized quite early this year. But this running comes with a significant challenge- icy conditions. Overnight lows in the teens and low 20’s F followed by 30-50 degree F sunny days produces glare ice conditions throughout our otherwise packed powder winter running trail system. This situation, in my experience, requires the use of metal spikes in or on running shoes.

As outlined previously with the Salomon SnowCross shoes, I have taken a pair of the Salomon SpikeCross shoes and turned them into a SpikeCross “Sense” by removing all of the heel lugs but leaving the 4 spikes in this area. The result is a lower drop version of the SpikeCross that, for those who prefer and use lower drop running shoes, really hits the mark for winter running on trails in icy conditions.


Salomon SpikeCross 3 before modification. These shoes were just sitting on a shelf not being used because the higher drop aggravates my Achilles tendon.


Salomon SpikeCross “Sense”: removal of the rear lugs drops the heel about 8-10 mm (the spikes just cut into the snow or dirt) making the overall drop about 5-7 mm. Note: the black rubber used on the SpikeCross proved to be a more formidable challenge for removal than the white rubber used on the SnowCross. Beyond a few choice words, removal is doable but difficult.

I now have in excess of 300 kms on these modified SpikeCross shoes and can report excellent results. No issues with the Achilles, exceptional grip on crusted snow and ice, and good performance on dirt.

Now, if only Salomon could see fit to bring out a Sense winter running shoe with spikes and an integrated gaiter…. in meantime these are working fine.

Salomon S Lab X-Series – Review – a nice addition to the S Lab group

I recently received a pair of Salomon S Lab X-Series a “new for 2015″ road shoe. As far back as I can remember, Salomon have never offered a road running shoe. And if they have offered a road shoe in the past, they certainly have not considered such shoes as a core part of the brand. So it was with a bit of apprehension that I slipped on the Salomon S Lab X-Series for some mixed miles of road and buffed trail. This apprehension soon evaporated into the unseasonably warm air here in the central Idaho mountains and was replaced by pure confidence in Salomon’s ability to enter the road shoe market.

Note: 3 April 2015- I have posted about a direct comparison of the X-series and the Sense 4 including a couple 100 miles (300 km) on each model both on trail and off-trail in a variety of conditions here.

Note:: 23 April 2015-  I have posted an update on the performance of the S Lab X-Series at about 700 km (435 miles) of use here.

Salomon X series overall

The Salomon S Lab X-Series- a road shoe from the trail experts.

The S Lab X-Series shoe is basically a road version of the Sense trail running shoe. What this means is that all of the fit technologies that make the Sense such a great trail shoe have been incorporated into the X-series along with a much cushier midsole and less aggressive outsole. The end result is outstanding.


The upper is constructed of materials and design that is expected for a road shoe that will not see much, if any, technical trail conditions. As such, the front portion of the upper is made of lycra with some side mesh panels on the outer side for ventilation. The rear portion of the upper and the inner side is made from a much beefier nylon as expected and needed for proper heel structure and protection from opposite shoe heel scuffing. The design includes no toe protection other than a small front bumper- you do not want to stub your toe on a rock in these shoes.

Salomon X Series side veiw


Th interior of the shoe incorporates the Endofit construction as is utilized in the S Lab Sense line of trail running shoes. This feature has received uniform rave reviews and general acceptance as a superior design element in current running shoes. The Endofit approach produces a secure yet very comfortable fit via an inner “sock”. This fit is often described as “slipper-like” and I concur.

Another feature to note is that the ankle cup topology is symmetric, meaning that the curved cup is the same on both the inner and outer sides. This is not the case for the Sense where the inner cup is taller than the outer cup as will be shown below.

Salomon x series ankle cup

Symmetric ankle cup in the Salomon S Lab X-Series.

The polymer overlay reinforcements take the familiar zig-zag shape but also wrap around the toe area for some minimal protection. The toe box is substantially wider than that in the Sense trail shoe line as will also be shown later.

Salomon X series viewed from above

View from above of the Salomon S Lab X-Series showing a toebox and forefoot that is wider than that in the Sense 4 Ultra.


Perhaps one of the most differentiated features of this shoe to the Sense line is the EVA cushioning. On Salomon’s 1-5 scale of “cushion” in their technical literature, the Sense 4 Ultra ranks at “1” whereas the X-Series is rated “5” where a larger number indicates more cushioning. This difference can be seen in the reported midsole thicknesses where the X-Series has a 19 mm heel and 11 mm forefoot EVA thickness whilst the Sense 4 Ultra has 13 mm heel and 9 mm forefoot thicknesses. So 6 mm more EVA at the heel and 2 mm more in the forefoot. Both models use the cushier “dual density” EVA construction (where a cushier EVA is strategically placed in a matrix of a less cushy formulation).

The X-Series also uses the ProFeel film technology developed for the Sense series shoes so there is good protection from rocks if one uses this shoe on trails.


The outsole of the X-Series is a hybrid trail/road configuration that combines some deep lugs asymmetrically with smoother areas of a design similar to other lightweight road shoes. Salomon claims that this design allows for both good grip on flat paved surfaces (wet or dry) as well as non-technical trails. There is also a deep cutout extending from the midsole into the heel region, which is likely a weight saving feature but may also provide additional longitudinal rigidity.

Salomon X series outsole

Outsole of the Salomon S Lab X-Series showing asymmetric tread pattern and deep lugs toward the outer portion of the forefoot. The wear layer is glued in numerous pieces to the EVA midsole, something which has proven to be problematic in the past- time will tell.

The outsole utilizes Salomon’s proprietary “Contragrip” polymer compound that has been in use on many Salomon models over the past few years. The wear layer is glued to the EVA midsole in segments much like the original Sense model of 2012. This gluing proved troublesome as the individual segments had a tendency to peel off and thereby limited the life of an otherwise sound shoe. Salomon seemed to fix this problem in the Sense 2 but went to a single molded piece in the Sense 3 (and 4). The single piece construction limits the linear area of exposed glue lines and seems to be a better choice for durability. Perhaps Salomon have figured out how to reliably use the segmented design but I will be casting a wary eye as I put miles on the X-Series.

Salomon S lab Sense 4 outsole

Salomon S lab Sense 4 Ultra outsole showing the single piece wear layer construction.

Running Geometry

The overall construction of the shoe has a significant “rocker” geometry similar to that found on many other trail and road shoes, and particularly on the Hoka line. The rocker geometry is said to better enable a forefoot strike when combined with a low drop. Many have noted favorably how well this has been executed on some of the Hoka models.

Salomon X seies side view

Side view of the Salomon S Lab X-Series showing the significant “rocker” element in the forefoot.

The drop of the X-Series is quoted as 8 mm with total stck heights of 23 mm heel and 15 mm forefoot. This drop is something of a hybrid between a “traditional” high heeled road shoe and a low drop trail shoe. I would prefer a lower drop but will defer judgement until I accumulate a significant volume of miles on the shoe.


The S Lab X-Series shoe is quoted as weighing in at 218 gms (7.7 oz) for a size 9 (US). My size 7.5 (US) (40 2/3 (EU)) tipped the scales at 215 gms (a little less than 7.6 oz). That is lighter than the quoted 238 gm for a size 9 (US) in the Sense 4 and the actual measurement of my Sense 4 Ultras in size 7.5 (US) at 227 gms, so a light shoe indeed. This is a good thing as weight matters- a lot, particularly for lighter weight (sub 125 lbs) runners like me.

Comparisons with S Lab Sense 4 Ultra

Since many of those who currently use the S Lab Sense shoe are likely to consider this shoe for road (and buffed trail) use, a comparison of the significant differences with the current Sense 4 Ultra model are presented below. The first comparison shows the larger toebox and forefoot area.

Salomon X series comparison forefoot

Comparison of the forefoot area of the Salomon S Lab Sense 4 Ultra (left) and the Salomon S Lab X-Series (right). Both the toebox and the forefoot width are larger.

A second comparison shows the substantial “rocker” geometry compared to the Sense 4 Ultra.

Salomon X series compared to Sense 4

Salomon S Lab X-Series (upper) and Salomon S Lab Sense 4 Ultra (lower) showing the substantial “rocker” geometry incorporated in the X-Series when compared to the Sense 4 Ultra.

A third comparison shows how similar the heel cup support structure is on both shoes.

Salomon S Lab X-series back comparison

Rear view of the Salomon S Lab Sense 4 Ultra (left) and the Salomon S Lab X-Series (right) showing similar heel support structure but very different ankle cup configurations.

However the ankle cup area is quite different with the X-Series having an symmetric cutout design whereas the Sense 4 Ultra has an asymmetric design and more rear roll-over in the padding.

Salomon X Series ankle cup comparison

Ankle cup comparison showing Salomon S lab Sense 4 Ultra (top) and Salomon S Lab X-Series bottom. The Sense 4 has an asymmetrical cup whereas the X-Series is symmetric. The Sense 4 also has much more rear roll-over of the padding.

Initial Running Impressions

I have had the X-Series shoe out for about 50 km of mixed use- about 30 km of road and 20 km of buffed trails. If you are a S Lab Sense user, you will note that the fit is very much like the very comfortable “slipper”-like feel of the Sense 3 and 4. The X-series is comfortable from the outset and I have noted no change in these first 50 kms. Also, if you are a Sense user you will immediately notice the “rocker” geometry and the way the shoe subtly prods your posture forward and on to the forefoot. I found this to be a nice feature of the Hoka Stinson trail shoe particularly given the maximal cushioning of that shoe. With the highly cushioned shoes there is the reality that when the cushion is deformed and your foot forms deep into this deformation one must overcome the not insignificant physical barrier thus created. The “rocker” geometry does a good job of dealing with this. And so it is also with the X-Series which has a much more padded midsole when compared to the Sense 4 Ultra.

Continuing with this, the second thing one will notice is the substantially greater cushion when compared to the Sense 3 and 4. On road surfaces this added cushioning is very apparent and quite welcome. It almost makes one want to actually consider running on roads from time to time (heresy!). On the trail the difference is not really noticeable although I have not taken the shoes on any technical and rocky stretches yet. Stay tuned.

I really like the feel of these shoes while running. The combination of fit, cushioning, geometry, traction, and weight seem to provide a near optimum balance between comfort and efficiency on roads. As far as trails, I will be giving these shoes a full workout once the snow recedes in the next few weeks. Based on these initial impressions, I think that this shoe will be a nice option to have available in ultra races where there is a lot of dirt road and/or buffed trail. I am likely to put these into a drop bag at an aid station in a 100 km race this year where the last 13 miles are a downhill charge into town on graded dirt roads. The cushioning and rocker geometry will be just the ticket!


$160 US. Steep but if these shoes last as long as the other S Lab shoes I have used then the “cents per mile metric” will be more than palatable. Only time will tell.

Bottom Line

A very nice entry by Salomon into the road shoe arena with all expectations that this shoe will be an outstanding performer- stay tuned.