Our verdict

The Superior 6 from Altra belongs to their line of zero-drop, low-stack trail shoes. We were excited to see it maintain its commitment to a grounded feel, offering stability and agility on various surfaces and inclines. However, we noticed in our lab tests that it sheds the optional StoneGuard insert found in its predecessors. We also found it slightly heavy for its stack height and the ride might be too firm for some. Yet, it stands out as a great choice for trail enthusiasts wanting a natural running experience without breaking the bank.

Pros

  • Exceptional ground feel for a more connected run
  • Nimble and quick
  • Excellent breathability
  • Upper and tongue designed for maximum comfort
  • Durable outsole with reliable grip
  • Remarkable stability
  • Comfortable for all-day wear
  • Reasonably priced

Cons

  • Lacks a rock plate
  • Not ideal for long distances
  • The upper could be more durable

Audience verdict

74
Bad!

Who should buy

We highly recommend the Altra Superior 6 for:

  • Altra fans looking for a low-profile trail runner that offers a natural, ground-connected feel.
  • Those seeking a trail shoe versatile enough to smoothly navigate sharp turns and adapt to varied terrains.
  • Runners who value a flexible, zero-drop design and need a shoe that's equally great at hiking and walking.

Altra Superior 6

Who should NOT buy

We discovered the Altra Superior 6 has a minimal stack height of just 22.0 mm for both the heel and forefoot, which we don't recommend for runners seeking underfoot cushioning, especially for longer distances.

For those enchanted by the allure of zero-drop shoes but craving more cushion, the Altra Olympus 5 is a better pick, boasting a Vibram outsole for an added bonus.

Altra Superior 6

Furthermore, we believe the Superior 6 may not satisfy those yearning for a softer ride, as its cushioning leans towards the firmer side. If a more plush, yet low-drop shoe is what you're after, we recommend exploring the Hoka Speedgoat 5 or the Saucony Peregrine 13 as better choices based on our lab tests.

Breathability

When we unboxed the Superior 6, it seemed like it might have low breathability due to its engineered upper. However, we were pleasantly surprised to find out we were mistaken.

During our smoke test, we noticed that the Superior 6's design allows heat and moisture to escape, particularly around the tongue area, earning it a top score (5/5) for breathability.

Our second test shed more light—literally. Despite the upper blocking it, which suggested poor breathability, the shoe proved otherwise. This test also revealed that the midfoot is well-structured, promising excellent stability. More on this later.

Altra Superior 6 microscope

In the lab, we always turn to the microscope for a closer look at the upper. Under magnification, the Superior 6's mesh appeared dense and lacked visible ventilation holes.

Altra Superior 6 microscope

Upon examining the entire upper, we found it to be well-padded for comfort and, as mentioned earlier, notably reinforced in the midfoot to ensure stability and prevent the feet from collapsing sideways.

Test results
Superior 6 5
Average 3.3
Compared to 76 trail running shoes
Number of shoes
1
Breathability
5

Durability

Toebox durability

Now we're putting the shoe through the wringer with our Dremel to check its durability across three tests, kicking things off with the upper.

The results were disappointing, to say the least. This means a dismal score of 1 out of 5.

Altra Superior 6 Toebox durability
Test results
Superior 6 1
Average 3.1
Compared to 56 trail running shoes
Number of shoes
1
Toebox durability
5

Heel padding durability

Things hardly seemed like they could get worse, yet the heel padding wasn't much of an improvement either.

Following our Dremel test, we ended up with what we'd consider a disappointing 2 out of 5 rating. Although not quite as bad as the previous outcome, Altra really needs to step up its game in these areas.

Altra Superior 6 Heel padding durability
Test results
Superior 6 2
Average 2.9
Compared to 54 trail running shoes
Number of shoes
1
Heel padding durability
5

Outsole hardness

Now let's talk about the outsole, beginning with its hardness.

Altra Superior 6 Outsole

With a measure of 91.0 HC, Altra clearly aimed for a tough formulation with its MaxTrac rubber. Let's find out if it lives up to our expectations.

Altra Superior 6 Outsole hardness
Test results
Superior 6 91.0 HC
Average 85.3 HC
We use an average of four tests. The photo shows one of those tests.
Compared to 99 trail running shoes
Number of shoes
72.5 HC
Outsole hardness
95.0 HC

Outsole durability

In a final opportunity for the Superior to demonstrate true durability, it certainly rose to the occasion, all thanks to the rugged MaxTrac rubber.

Following our third and conclusive Dremel test, we observed a mere 0.6-mm indentation—an encouraging sign for those who enjoy long-lasting outsoles in trail shoes.

Altra Superior 6 Outsole durability
Test results
Superior 6 0.6 mm
Average 0.9 mm
Compared to 49 trail running shoes
Number of shoes
0.0 mm
Outsole wear
2.0 mm

Outsole thickness

If outsole durability tops your list of concerns, we believe the Superior will surely impress you, provided you're okay with its less durable upper, of course.

With a 3.0 mm outsole plus the lugs, even the most demanding trail runners will struggle to wear down the MaxTrac rubber.

Altra Superior 6 Outsole thickness
Test results
Superior 6 3.0 mm
Average 2.4 mm
Compared to 99 trail running shoes
Number of shoes
0.9 mm
Outsole thickness
6.5 mm

Weight

Turning our attention back to the outsole, it's time for us in the lab to measure the lugs. The Superior features 3.6-mm lugs designed to perform well on various terrains, particularly excelling on easy trails, gravel paths, and fire roads.

Altra Superior 6 Outsole

The outsole features strategic cutouts to reduce weight and enhance flexibility.

However, for muddy trails, we believe the lugs might be a bit short, though they should suffice for occasional use.

Weight

Although the Superior isn't designed as a racing shoe and doesn't have the heft of a tank, we anticipated it to weigh less than 9.6 oz (272g). It's not exactly a letdown, but given its stack height, we expected it to be lighter...

Altra Superior 6 Weight
Test results
Superior 6 9.59 oz (272g)
Average 10.34 oz (293g)
Compared to 99 trail running shoes
Number of shoes
7.51 oz (213g)
Weight
13.37 oz (379g)

Cushioning

Heel stack

And here's the proof of the low profile that we just mentioned before.

Altra Superior 6 profile

At only 22.1 mm in the heel, this is indeed a thin shoe that caters to trail runners that favor agility and being connected to the ground.

Altra Superior 6 Heel stack
Test results
Superior 6 22.1 mm
Average 32.2 mm
Compared to 99 trail running shoes
Number of shoes
16.1 mm
Heel stack
42.4 mm

Forefoot stack

In the forefoot, we discovered a stack height of 22.0 mm, just what we expected from the brand best known for embracing the zero-drop philosophy.

Altra Superior 6 Forefoot stack
Test results
Superior 6 22.0 mm
Average 24.4 mm
Compared to 99 trail running shoes
Number of shoes
15.2 mm
Forefoot stack
33.9 mm

Drop

The minimal, 0.1-mm difference between the forefoot and heel is a huge win for those in pursuit of the ultimate zero-drop trail running experience.

It's not uncommon for the actual drop to deviate from what brands advertise, but in this case, it aligns almost perfectly.

Altra Superior 6 Drop
Test results
Superior 6 0.1 mm
Average 7.8 mm
Compared to 98 trail running shoes
Number of shoes
-0.1 mm
Drop
17.3 mm

Insole thickness

The insole is crafted from EVA and has a standard thickness of 4.4 mm, making it feel comparable to most shoes on the market.

Altra Superior 6 Insole thickness
Test results
Superior 6 4.4 mm
Average 4.7 mm
Compared to 99 trail running shoes
Number of shoes
2.7 mm
Insole thickness
9.8 mm

Midsole softness

Note: a low durometer measurement equals a soft material, whereas a high measurement means it's firm.

The midsole definitely has a firm feel from the Quantic foam, which is what we anticipate from an Altra, especially in a low-profile shoe like the Superior. If it were any softer, the shoe would bottom out with every step, which would be problematic.

This is particularly true since the Superior, for the first time in the series, doesn't include the StoneGuard insert. Without this optional protection, a softer foam would make for a potentially unpleasant experience, allowing rocks to press uncomfortably against your metatarsals with each stride.

Altra Superior 6 Midsole softness
Test results
Superior 6 29.1 HA
Average 23.2 HA
We use an average of four tests. The photo shows one of those tests.
Compared to 75 trail running shoes
Number of shoes
9.4 HA
Midsole softness (soft to firm)
39.0 HA

Difference in midsole softness in cold

Based on its top-notch breathability score, this shoe might not be the ideal choice for winter runs.

However, if you're considering it for cold weather, our tests showed that after spending 20 minutes in the freezer, the foam became 26.6% firmer, making it feel almost like titanium under your feet.

Altra Superior 6 Difference in midsole softness in cold
Test results
Superior 6 26.6%
Average 26.7%
Compared to 75 trail running shoes
Number of shoes
0%
Difference in midsole softness in cold
100%

Stability

Lateral stability test

With its slim stack height and solid midsole, combined with the side reinforcements in the upper we mentioned earlier in this lab review, the outcome was inevitable.

The Superior boasts outstanding stability for a neutral shoe, free from any intrusive features like rigid plastic pieces.

Torsional rigidity

We were happy by how effortlessly the Superior flexed and twisted during our hands-on evaluation, earning it a solid 3 out of 5 score.

Thanks to its inherent stability, Altra's designers were able to keep the shoe flexible, enhancing its agility for sharp turns and adapting to tough terrain. This makes it an excellent choice for steep, downhill singletracks.

Test results
Superior 6 3
Average 3.5
Compared to 93 trail running shoes
Number of shoes
1
Torsional rigidity
5

Heel counter stiffness

The heel counter is exceptionally comfortable and flexible, making the Superior a treat for anyone requiring a soft heel area to prevent Achilles tendon irritation. We gave it a 2 out of 5 rating.

Test results
Superior 6 2
Average 3.2
Compared to 91 trail running shoes
Number of shoes
1
Heel counter stiffness
5

Midsole width in the forefoot

Now, let's discuss the shoe's dimensions. Given its low profile and close connection to the ground, we think designing a wide shoe is unnecessary and not worth the added weight.

Altra Superior 6 forefoot

The Superior 6, measuring 113.0 mm in the widest part of the forefoot, is average in width, which works well for this shoe.

Test results
Superior 6 113.0 mm
Average 111.9 mm
Compared to 99 trail running shoes
Number of shoes
102.1 mm
Midsole width in the forefoot
126.0 mm

Midsole width in the heel

We noticed that the heel follows the same design approach, striking a balance without being too narrow or too wide, measuring just 86.1 mm.

Altra Superior 6 Midsole width in the heel
Test results
Superior 6 86.1 mm
Average 89.6 mm
Compared to 99 trail running shoes
Number of shoes
77.2 mm
Midsole width in the heel
109.3 mm

Flexibility

Stiffness

Earlier in this lab review, we discovered the Superior 6 to be incredibly flexible, but we had one final test to conduct in this area—the 90-degree bend test. In this test, we bend the shoe to the desired angle and measure the force required using our force meter.

The result was just 17.7N, confirming this shoe as exceptionally flexible and a joy for those who prefer a natural feel in their stride. This flexibility also makes it outstanding for hiking or casual walking.

Test results
Superior 6 17.7N
Average 28.6N
We use an average of four tests. The video shows one of those tests.
Compared to 99 trail running shoes
Number of shoes
10.5N
Stiffness
54.5N

Difference in stiffness in cold

We did the 20-minute freezer test again to see how stiff the shoe gets in cold winter conditions. Afterward, it took 33.3% more effort to bend the shoe, yet it remained quite flexible, needing only 23.6N of force.

Test results
Superior 6 33.3%
Average 35.7%
Compared to 96 trail running shoes
Number of shoes
0%
Difference in stiffness in cold
102%

Grip / Traction

Lug depth

Turning our attention back to the outsole, it's time for us in the lab to measure the lugs. The Superior features 3.6-mm lugs designed to perform well on various terrains, particularly excelling on easy trails, gravel paths, and fire roads.

Altra Superior 6 Outsole

The outsole features strategic cutouts to reduce weight and enhance flexibility.

However, for muddy trails, we believe the lugs might be a bit short, though they should suffice for occasional use.

Altra Superior 6 Lug depth
Test results
Superior 6 3.3 mm
Average 3.5 mm
Compared to 99 trail running shoes
Number of shoes
1.7 mm
Lug depth
5.8 mm

Size and fit

Toebox width at the widest part

The upper is a crucial component of every Altra shoe, with fans of the brand expecting a spacious and comfortable fit. So, does the Superior 6 meet these expectations?

While the widest part of the upper may not feel exceptionally spacious for this brand, after our hands-on experience, we believe it's certainly adequate for most feet. We measured it at 100.4 mm.

Altra Superior 6 Toebox width at the widest part
Test results
Superior 6 100.4 mm
Average 98.7 mm
Compared to 99 trail running shoes
Number of shoes
92.0 mm
Toebox width at the widest part
104.9 mm

Toebox width at the big toe

However, it's in the toe area where every Altra truly shines, thanks to their unique, Footshape toeboxes.

Altra Superior 6 Footshape

This is why the measurement we took in the big toe area was an impressive 89.5 mm, which is absolutely astonishing when compared to trail shoes from other brands.

Altra Superior 6 Toebox width at the big toe
Test results
Superior 6 89.5 mm
Average 78.9 mm
Compared to 61 trail running shoes
Number of shoes
70.5 mm
Toebox width at the big toe
92.1 mm

Tongue: gusset type

We discovered that the tongue is securely attached to the sides, a delightful surprise for a shoe priced at £140. Typically, we encounter non-gusseted tongues in this price bracket, so this feature is a noteworthy upgrade.

The tongue also stands out from most shoes, as it's seamlessly integrated with the upper, blending smoothly into the toe box. This design is particularly good for a trail shoe, as the combination with the gusset effectively blocks debris and small rocks from entering the shoe.

Altra Superior 6 Tongue: gusset type
Test results
Superior 6 Both sides (full)

Comfort

Tongue padding

The 6.9-mm tongue is arguably the highlight of this shoe, featuring just the right amount of padding in the perfect spot.

Altra Superior 6 tongue

It strikes a brilliant balance—not so much that it becomes heavy, but enough to ensure it doesn't compromise on comfort.

Altra Superior 6 Tongue padding
Test results
Superior 6 6.9 mm
Average 6.4 mm
Compared to 99 trail running shoes
Number of shoes
1.5 mm
Tongue padding
12.2 mm

Heel tab

The heel on the Superior 6 sports a huge horizontal tab. Normally, we'd call this kind of thing a finger loop (singular), but this one's got space for at least three fingers!

Altra Superior 6 Heel tab
Test results
Superior 6 Finger loop

Removable insole

The insole isn't glued down, so you can easily change it. But because of the unique, foot-shape design of the toebox means most OTC orthotics won't fit this Altra just right. You might need to get a custom-made one.

Altra Superior 6 Removable insole
Test results
Superior 6 Yes

Misc

Reflective elements

The Superior 6 doesn't have any reflective features. But at just £140, that's not a big deal.

Altra Superior 6 Reflective elements
Test results
Superior 6 No