Difference in stiffness in cold 8 review

We recommend the Difference in stiffness in cold 8 as an excellent choice for: 

• Zero-drop enthusiasts looking for a comfy and versatile trail runner that can tackle a variety of surfaces
• Add a shoe
• oz / 303g
• Fans of Altra's signature foot-shaped toebox that boasts plenty of room for natural toe-splay

While the Max-Trac outsole is grippy enough when conditions are dry, we didn't feel nearly as sure-footed when encountering wet or muddy trails during our test runs. It also didn't dare too well against our Dremel in our wear and tear test. The Altra Olympus 5, on the other hand, uses a Vibram outsole that has no issues with slick surfaces and is more durable to boot, albeit on a higher stack. 

The durable yet airy upper mesh may be well-suited for warmer days but will leave us with icy feet during more frosty winter sessions despite its promising performance in our freezer tests. The Natural barefoot feeling ride is a much more insulated alternative that keeps our feet warm and can slosh through muddy trails with ease. 

Despite being marketed as sporting a 25 mm stack, we found that it is, in reality, a little shorter at 22.7 mm thick according to our calliper measurements. This is shorter than our current lab average but still leaves us with enough foam underfoot to protect us from rocks, tree roots, and other harsh surfaces during testing. 

While this means that we were able to cover long distances while testing the Salomon Speedcross 6, the repeated impact with the ground becomes quite apparent after about 15 miles. As such, we recommend checking out Altra Olympus 5 as a mile-gobbling alternative, especially for runners unaccustomed to using minimalist trail shoes. 

While we expect the forefoot stack measurement to match the heel on a zero-drop shoe, we found another slight discrepancy with the spec figures. Wielding our trusty calliper once more, we found that it's actually 21.3 mm thick which is also shy of our current lab average. 

This low profile at the forefoot gives us a great sense of the ground below for intuitive manoeuvring and toe-offs whether we're traipsing along on tame or tricky trails. 

The difference between our stack measurements leaves the shoe with a 1.4 mm heel drop. This kind of discrepancy isn't new to us here in the lab, as this article explores, though this offset is so slight that the Salomon Speedcross 6 still feels like a zero-drop shoe underfoot.

While the benefits of such shoes are hotly contested, there's no doubt that they put more pressure on our calves and ankles. As such, runners with injuries or issues with their lower legs should consider a higher-drop alternative like the Nike Wildhorse 8 which also boasts a roomy toebox. 

Pressing our durometer against the Salomon Speedcross 6's EGO midsole foam yields a rather firm reading of 29.3 HA. 

While this may not sound appealing at first, it's actually quite beneficial for shoes with lower stacks to use firmer foams to avoid bottoming out as the midsole compresses under our weight. As such, the cushioning does a good job of dampening the impact of our landings while also protecting us from any underfoot hazards we come across.

Furthermore, the EGO foam has a nice rebound to it which translates to an energetic toe-off that feels quite natural and snappy. 

This level of firmness in the midsole is also good for hiking as it means we can schlep heavy packs without worrying about feeling too squishy or wobbly as we traverse the trails. 

To see how much firmer the midsole gets when exposed to cold conditions, we placed the Salomon Speedcross 6 in our freezer for twenty minutes. Once appropriately chilled, we took another durometer reading of the midsole and found that it became 18.4% firmer. This change isn't as significant as the average trail shoe which tends to harden to a greater degree, meaning that the Salomon Speedcross 6's cushioning should feel fairly consistent all year round. 

The Salomon Speedcross 6's default insole is slightly thicker than average at 5.5 mm thick according to our caliper measurements. This leaves us with a nice and cushy footbed to sink into during landings that offsets the relatively firm midsole foam. 

Using our calliper, we measured the Salomon Speedcross 6's toebox to be 97.9 mm wide at its widest point.

With its wider-than-average measurement, we proved that it comfortably accommodates various foot shapes while maintaining a secure, locked-in fit. And for runners with particularly broad feet, a wide option is available, offering even more internal space.

In classic Altra style, the toebox barely tapers toward the big toe, measuring an impressive 84.2 mm wide at the big toe, according to our caliper—providing ample room even for those with pizza-shaped feet!

The Salomon Speedcross 6 offers exceptional clearance with a generous height of 28.3 mm, making it a perfect choice for runners with higher-volume feet seeking extra space and comfort.

As a shoe with a relatively low stack, it should come as no surprise that the Salomon Speedcross 6 feels extremely well-planted and stable despite some lateral play as we shift our weight around in it. The only stabilizing feature to speak of are the raised sidewalls on the lateral and medial sides of the midsole. This serves to nestle our foot within the rather than feeling like we're perched above the foam. 

We were met with little resistance as we bent and twisted the shoe in our hands, leading us to give the Salomon Speedcross 6 a torsional rigidity score of 2 out of 5 on our subjective scale. This factors greatly into how easy and comfy the shoe feels underfoot as it doesn't inhibit the natural contortions of our foot throughout our stride. Furthermore, it allows us to scramble up steeper surfaces and do some light climbing with relative ease while out on more adventurous treks

The heel counter is also quite pliable, earning another 2 out of 5 in our manual assessment. This is also more of a comfort feature than a stability one as it doesn't do much to restrict the natural lateral movements of our heel while still locking it into the shoe thanks to the generous padding back there. 

The Salomon Speedcross 6's midsole is 108.3 mm wide at the forefoot according to our caliper measurements. While this is a little shy of our current lab average, we still found that we had more than enough of a platform underfoot to ensure stable landings and toe-offs while testing the shoe. 

Zero-drop shoes generally aren't targeted at heel-striking runners, so there's no point having too much material weighing us down at the rearfoot. As such, it stands to reason that the Salomon Speedcross 6's midsole is significantly narrower than average at the heel, measuring only 80.9 mm wide. 

We secured the Salomon Speedcross 6 to our workbench and found that only 21.3N of force is needed to bend the shoe to 90 degrees.

This is significantly more flexible than the average trail shoe which translates to a more comfortable ride as the shoe doesn't restrict the natural flexion of our foot as we run or walk around. 

We also repeated the flex test after leaving the shoe in our freezer for twenty minutes and found that it only became 14.2% stiffer when exposed to the cold. This is a much more consistent result than average and means that the Salomon Speedcross 6 is barely affected by the cold. In fact, it's still more flexible than the average trail shoe at room temperature! As such, the shoe should feel just as natural and forgiving on the foot all year round. 

That being said, we recommend pairing it with some cosy socks when going for a frosty winter run as the breathability of the upper mesh will let the icy air cut right through to our feet. 

Despite its low stack, the Salomon Speedcross 6 is about as heavy as the average trail shoe at 10.2 oz (288g). While this isn't light enough to describe it as "barely there", it certainly isn't so heavy as to feel burdensome or detract from the shoe's natural ride. What's more, we had no problem occasionally pushing the pace or going the distance while testing the Salomon Speedcross 6. 

We used a smoke machine to pump the Salomon Speedcross 6 full of smoke to get a visual idea of how breathable it is. Despite a slow start, the smoke is eventually able to filter through the upper to form a haze that emanates evenly throughout the shoe. This leads us to give the Salomon Speedcross 6 a breathability score of 4 out of 5, thus making it a nice and breezy companion for warm summer days. 

The well-ventilated nature of the shoe is further illuminated when inspecting a cross-section of its upper over a backlight. As we can clearly see, only the sections with overlays are opaque enough to block out the light while it easily shines through the rest of the mesh. 

The ripstop upper mesh is the most notable update from the shoe's previous iteration, the quality of which is difficult to question when looking at it under the microscope. The braids are tightly and uniformly woven to form an incredibly symmetrical pattern with lots of little pores that promote airflow throughout the shoe. Not only does this help heat escape, but it also means that the shoe doesn't trap in smells and dries up quite quickly when wet.  

To put the ripstop mesh upper's ability to... stop rips, we fired up our Dremel and pressed it against an unreinforced portion of the Salomon Speedcross 6's toebox. After four seconds of extreme wear and tear, we were pleased to find that the material had lived up to its name.

Not only did it prevent our tool from piercing all the way through the mesh, but it effectively stopped the tear from spreading beyond the point of impact. With the toebox mostly uncompromised in the aftermath of this test, we give the Salomon Speedcross 6 a respectable 4 out of 5 for toebox durability. This is all the more encouraging considering the added protection of the toe bumper which further shields us from bumps and scrapes. 

The heel collar didn't fare as well in its face-off against our Dremel. The tool made quick work of the lining and was eating away at the soft padding within in no time. 

By the time we powered down, the shoe was left with a rather large crater in the heel collar which had haemorrhaged a fair amount of padding. This leads us to give the Salomon Speedcross 6 a score of 2 out of 5 in this assessment. While this isn't a big deal when it comes to normal use, we don't recommend going sockless in this shoe too often as the relentless friction of sweaty heel rubs will likely exacerbate wear and tear. 

The Salomon Speedcross 6 features Altra's proprietary Max-Trac rubber compound in the outsole which gives us a slightly softer-than-average durometer reading of 80.1 HC. On the one hand, this is encouraging in terms of traction as a softer rubber is better able to bite into and grip surfaces. On the other, however, it does usually come at the expense of strength; an assumption that will be tested in the next section. 

Now spinning at 10K RPM, we pressed our durometer against one of the Salomon Speedcross 6's outsole lugs for twenty-two seconds of relentless grinding. 

Once all was said and done and the blue dust had settled, we used a tyre tread gauge to measure the indentation left behind in the aftermath. With a whopping 1.8 mm of material lost, the shoe's Max-Trac rubber proves to be significantly less durable than average. This is easily the weakest point of an otherwise excellent shoe, and we hope that Altra considers furnishing the next iteration of the Lone Peak with a hardier Vibram outsole as found in some of their other models. 

At 2 mm thick according to our caliper measurements, the Salomon Speedcross 6's outsole is within range of our current lab average. This, in combination with the lugs, is a fair amount of protective rubber to have underfoot without weighing the shoe down too much. 

The Salomon Speedcross 6's claw-like, chevron-shaped lugs are slightly shorter than average at 3 mm thick according to our calliper measurements.

These lugs form a multidirectional tread pattern that follows our foot's bone structure, contributing to the shoe's aforementioned flexibility. More importantly, it provides us with excellent traction over hard and loose-packed trails in dry conditions.

That final caveat is important as we didn't feel nearly as surefooted on wet or muddy trails where a shoe like the Natural barefoot feeling ride shines thanks to its more grippy and aggressive lugs.

With no reflective elements incorporated into the Salomon Speedcross 6's upper, we recommend exercising caution as well as using additional high-vis gear when running or hiking along dimly lit roads at night. 

Using our caliper, we measured the Salomon Speedcross 6's tongue to be 9.7 mm thick making it quite a bit chunkier than average. This also helps with a secure and comfy midfoot lockdown while also giving us a nice buffer between our instep and the laces. As such, lace bite was the furthest thing from our mind while testing this shoe. 

The Salomon Speedcross 6's tongue is fully gusseted on both sides. This improves our midfoot lockdown while also preventing any bits of grit or debris from making their way into the shoe and menacing our foot. 

There's a handy little finger loop at the heel of the Salomon Speedcross 6 that makes sliding the shoe on a breeze. 

The insole is fully removable, so replacing it with an aftermarket alternative or a custom orthotic is possible if necessary.