Our verdict

We found the Altra oz / 264g to be a fantastic carbon-plated racing shoe for trails, distinct from its competitors. It boasts a zero-drop midsole, a flat-and-flexible carbon plate, and ample room for your toes. During our tests, we appreciated the comfortable and high-quality upper coupled with the excellent Vibram Megagrip outsole. However, we think it falls short as a true supershoe because the midsole lacks sufficient energy return, and we found the price to be on the higher side.

Pros

  • True Altra DNA!
  • Responsive and fast
  • Superior Vibram Megagrip outsole
  • Excellent durability
  • Remarkably lightweight
  • which boasts a full-length ZoomX midsole for superior performance
  • Rounded, anatomic toe cap
  • Adaptable across various paces

Cons

  • Limited energy return
  • Priced high

Audience verdict

88
Great!

Who should buy

After pushing the oz / 264g to its limits, we highly recommend it for:

  • Midsole softness soft to firm.
  • Forefoot or midfoot strikers who appreciate a Vibram outsole and a roomy upper in a performance-oriented shoe.
  • Anyone looking for a carbon-plated trail shoe that still offers flexibility and comfort, rather than stiffness—truly a gem in today's market.

Altra oz / 264g

Who should NOT buy

We do not recommend the oz / 264g for those seeking peak performance on trails—it falls short due to its mid-tier foam, which lacks optimal energy return, and its flat carbon plate that doesn't aggressively enhance propulsion. Instead, we suggest checking out the Nike Ultrafly, which boasts a full-length ZoomX midsole for superior performance.

Additionally, we believe the oz / 264g is not the best choice for heel strikers—the 0-mm heel-to-toe drop and non-rockered geometry may slow you down and cause discomfort in your calves or Achilles. For heel strikers, we recommend the Hoka Tecton X 2, which offers similar features with a low drop configuration but is much better suited for those who strike with their heel first.

Altra oz / 264g parts

Breathability

The oz / 264g features an ultra-thin, monomesh upper, which ensures that, despite lacking large ventilation holes, it still offers decent breathability.

In our tests using a smoke-pumping machine, we observed that the toebox can expel a small amount of heat and humidity, while the bulk escapes through the tongue—sufficient for us to rate this shoe a solid 3 out of 5. This score reflects a good design for a trail kick.

With the aid of a light, we pinpointed the surprising thinness of the upper and the substantial structural reinforcements included to enhance stability.

Altra oz / 264g microscope

Next, we examined the engineered mesh under a microscope to get a closer look.

Altra oz / 264g micro 2

What we love most about using the microscope is how differently the upper appears. We were able to identify the tiny ventilation holes spaced a few millimetres apart.

Finally, we inspected the sliced upper. For a race shoe, we believe that it's adequately padded and that the build quality is comparable to other Altra shoes.

Test results
oz / 264g 3
Average 3.3
Compared to 82 trail running shoes
Midsole softness soft to firm
1
Breathability
5

Durability

Toebox durability

As a proper trail running shoe, the Mont Blanc Racer boasts TPU overlays on the toecap, enhancing its ruggedness. Besides, we conducted our Dremel test on the mesh—typically the upper's most delicate area.

Even though we tested the weakest part of the upper, we found the results to be good, earning a solid 3 out of 5. This score is more than sufficient for a trail racer, confirming that it successfully passes our rigorous testing standards.

Altra oz / 264g Toebox durability
Test results
oz / 264g 3
Average 3
Compared to 62 trail running shoes
Midsole softness soft to firm
1
Toebox durability
5

Heel padding durability

The heel padding is very exposed and appeared fragile from the first look, prompting us to brace for a disappointing performance in this area.

As it turned out, the Dremel test obliterated the heel padding, handing the MBC a dismal 1 out of 5 in this assessment. This result raises significant concerns about heel slippage and the shoe's durability, especially for those who tend to wear down this area with their Achilles.

Altra oz / 264g Heel padding durability
Test results
oz / 264g 1
Average 2.9
Compared to 60 trail running shoes
Midsole softness soft to firm
1
Heel padding durability
5

Outsole hardness

After mixed results with the upper, we were keen to evaluate the outsole—one of the most critical components of trail running shoes. Our initial impression was promising, as we identified the Vibram logo and the Megagrip Litebase compound, which usually means excellent performance and lightness.

Altra oz / 264g Vibram

This shoe features the Altra's Natural Ride System, which features metatarsal-specific contours in the outsole. These elements are crafted to promote a more natural movement of the foot.

We then measured the hardness of this specific Vibram Megagrip formulation and discovered that at 88.3 HC, it closely matches that of other Vibram-equipped shoes, such as the Hoka Mafate Speed 4.

Altra oz / 264g Outsole hardness
Test results
oz / 264g 88.3 HC
Average 85.4 HC
We use an average of four tests. The photo shows one of those tests.
Compared to 105 trail running shoes
Midsole softness soft to firm
72.5 HC
Outsole hardness
95.0 HC

Outsole durability

Both sides full.

The results exceeded our expectations. We found a minimal dent of just 0.6mm in the lug—this impressive performance assures that you'll likely get bored of the oz / 264g long before the outsole shows any significant wear.

Altra oz / 264g Outsole durability
Test results
oz / 264g 0.6 mm
Average 0.9 mm
Compared to 55 trail running shoes
Midsole softness soft to firm
0.0 mm
Outsole wear
2.0 mm

Outsole thickness

Given the exceptional performance of the Vibram Megagrip rubber, we were not surprised to find a minimal outsole thickness of just 0.9mm.

There's no need for a thicker outsole when durability is already assured—increasing thickness would only add unnecessary weight. Additionally, the full-length carbon plate in the midsole acts as a rock plate and ensures ample protection for your feet.

Altra oz / 264g Outsole thickness
Test results
oz / 264g 0.9 mm
Average 2.4 mm
Compared to 105 trail running shoes
Midsole softness soft to firm
0.9 mm
Outsole thickness
6.5 mm

Weight

Speaking of weight, we discovered that the oz / 264g is exceptionally lightweight, tipping the scales at just 8.9 oz or 251g.

This is a good weight for being a trail shoe, considering the lugs, and protective features can add up to 2 ounces.

Altra oz / 264g Weight
Test results
oz / 264g 8.85 oz (251g)
Average 10.30 oz (292g)
Compared to 105 trail running shoes
Midsole softness soft to firm
7.51 oz (213g)
Weight
13.37 oz (379g)

Cushioning

Heel stack

Altra advertises the heel stack at 29 mm, yet our precise measurements showed it to be slightly less at 27.2 mm. This minor discrepancy is virtually undetectable during a run.

While less than 30 mm might seem modest for a racing shoe, it's important to remember that Altras are designed for midfoot and forefoot strikers. Therefore, avoiding maximalist cushioning in the heel is a good idea, as it prevents unnecessary weight, enhancing the shoe's overall performance.

Altra oz / 264g Heel stack
Test results
oz / 264g 27.2 mm
Average 32.2 mm
Compared to 105 trail running shoes
Midsole softness soft to firm
16.1 mm
Heel stack
42.4 mm

Forefoot stack

The forefoot boasts a 26.9 mm stack, aligning it with competitors in the carbon-plated category, such as the Saucony Endorphin Edge.

While some individuals tackling pancake-flat ultras might prefer a bit more stack, most trail races cover a diverse range of terrains. This design choice is prudent, allowing runners to conserve his legs while maintaining good stability and agility.

In trail running, compromises are unavoidable...

Altra oz / 264g Forefoot stack
Test results
oz / 264g 26.9 mm
Average 24.5 mm
Compared to 105 trail running shoes
Midsole softness soft to firm
15.2 mm
Forefoot stack
33.9 mm

Drop

The difference between our previous two measurements results in a 0.3-mm heel-to-toe drop, remarkably close to the official 0.0 mm that Altra claims for the oz / 264g.

This slight variation is not a concern for us. Moreover, it's well within typical manufacturing tolerances, or even the slight shifts that can occur simply from using the shoe for a few runs. In fact, it's quite common for us to encounter differences of 3 or 4 mm in our measurements!

Altra oz / 264g Drop
Test results
oz / 264g 0.3 mm
Average 7.8 mm
Compared to 104 trail running shoes
Midsole softness soft to firm
-0.1 mm
Drop
17.3 mm

Insole thickness

The insole of this shoe maintains a straightforward thickness at 4.5 mm—there’s not much that stands out about it. However, it’s worth noting that it’s somewhat thicker than the typical insoles found in racing shoes, which usually measure between 2 and 3 mm.

Altra oz / 264g Insole thickness
Test results
oz / 264g 4.6 mm
Average 4.7 mm
Compared to 105 trail running shoes
Midsole softness soft to firm
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 of the oz / 264g is interesting, featuring not just one, but two distinct types of foam. The primary foam is EGO MAX (19.6 HA), a blend of EVA and TPU, which serves as the base for the EGO PRO layer that we'll discuss shortly.

From our perspective, the EGO MAX foam represents one of the weaker aspects of the shoe, preventing us from classifying it as a true supershoe. Additionally, considering the £260 price tag, we feel that a midsole composed entirely of PEBA would be more fitting, though it seems we may have to wait until v2 for such an upgrade.

Altra oz / 264g Midsole softness
Test results
oz / 264g 19.6 HA
Average 22.7 HA
We use an average of four tests. The photo shows one of those tests.
Compared to 81 trail running shoes
Midsole softness soft to firm
9.1 HA
Midsole softness (soft to firm)
39.0 HA

Secondary foam softness

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

The secondary foam, which is white, sits above the plate and is only visible once the shoe is cut in half. So, it's no surprise if this is the first time you're hearing about it in a review of the oz / 264g.

Although it has the same balanced softness at 19.6 HA, this foam is distinctly different—bouncier than EGO MAX and made from TPE, not the EVA and TPU blend. In our view, a full-length EGO PRO layer would have been a better choice for this shoe while Altra develops a PEBA foam.

Altra oz / 264g Secondary foam softness
Test results
oz / 264g 19.6 HA
Average 24.7 HA
We use an average of four tests. The photo shows one of those tests.

Difference in midsole softness in cold

We discovered that the oz / 264g becomes 32.5% firmer after spending 20 minutes next to our ice creams in the freezer.

It's truly disappointing to see such subpar performance in this test, especially given the high cost of the shoe. But since the main foam contains EVA as its primary component, there’s an unavoidable decline in softness under freezing conditions.

Altra oz / 264g Difference in midsole softness in cold
Test results
oz / 264g 32.5%
Average 26.5%
Compared to 81 trail running shoes
Midsole softness soft to firm
0%
Difference in midsole softness in cold
100%

Plate

The name "Carbon" in oz / 264g stems from the inclusion of a carbon-fibre plate, a highly anticipated feature by Altra fans. And it’s here, though it's not your average plate.

Upon cutting the shoe in half, we discovered that the plate’s geometry is very flat, instead of being curved at the forefoot. This design choice prioritises stability over other speed, which is not a bad thing at all, especially for trail running. But dont expect the quick turnover featured by a spoon-shaped plate like the one in a Stiffness in cold.

Altra oz / 264g Plate

Stability

Lateral stability test

The MBC may not be the most stable trail shoe on the market, but it performs good enough for us, especially considering its narrower build.

It was during our test runs that we realised the importance of the flat plate—it plays a crucial role in providing additional support for this shoe.

Torsional rigidity

One of the remarkable features of this running shoe is its incredible flexibility, despite incorporating a carbon plate. You might be puzzled—how is this possible? How did it score a 2/5 on our torsional rigidity test when other carbon-plated shoes typically score 4/5 or 5/5 and feel rigid like steel?

Altra oz / 264g Carbitex

The answer lies in the collaboration between Altra and Carbitex. Altra requested a flexible carbon plate, and Carbitex responded by engineering a revolutionary plate named Monoflex. Despite being made of carbon fibre, it flexes and bends torsionally and longitudinally, much like a plastic plate.

Test results
oz / 264g 2
Average 3.5
Compared to 99 trail running shoes
Midsole softness soft to firm
1
Torsional rigidity
5

Heel counter stiffness

oz / 277g road racing shoes—it's very flexible and easily collapses under the force of our hand.

That's why we gave it a low rating, just slightly above the minimum, at 2/5.

Test results
oz / 264g 2
Average 3.2
Compared to 97 trail running shoes
Midsole softness soft to firm
1
Heel counter stiffness
5

Midsole width in the forefoot

The midsole of the Altra oz / 264g at the forefoot measures 113.4 mm, aligning with many other trail shoes. This width strikes an ideal balance in our view—not overly bulky, yet wide enough to enhance stability underfoot, which we found to be a wise design choice during our test runs.

Altra oz / 264g Midsole width in the forefoot
Test results
oz / 264g 113.4 mm
Average 112.0 mm
Compared to 105 trail running shoes
Midsole softness soft to firm
102.1 mm
Midsole width in the forefoot
126.0 mm

Midsole width in the heel

As we previously mentioned in this lab review, we do not recommend this shoe for heel strikers due to its very narrow heel area (84.3 mm). Conversely, this feature is advantageous for forefoot and midfoot strikers as it enhances agility and reduces weight, making it easier to take corners and execute fast turns.

Altra oz / 264g Midsole width in the heel
Test results
oz / 264g 84.3 mm
Average 89.7 mm
Compared to 105 trail running shoes
Midsole softness soft to firm
77.2 mm
Midsole width in the heel
109.3 mm

Flexibility

Stiffness

As we demonstrated in our previous torsional rigidity tests, the Carbitex Monoflex plate in the MBC offers remarkable flexibility. This was further confirmed in our 90-degree bend test, where our force gauge recorded only 22.9N—lower than many plateless shoes!

This means that, despite being equipped with a carbon plate, the shoe feels exceptionally comfortable underfoot. It performs well at slower paces and is equally comfortable for walking.

Test results
oz / 264g 22.9N
Average 28.1N
We use an average of four tests. The video shows one of those tests.
Compared to 105 trail running shoes
Midsole softness soft to firm
10.5N
Stiffness
54.5N

Heel stack brand

We repeated the test after placing the shoe in the freezer for 20 minutes to see if the stiffness changed under cold temperatures.

After re-measuring with the force gauge, the result showed only a 26% increase in stiffness, which is a positive outcome in our view, likely due to the presence of the carbon plate.

Test results
oz / 264g 26%
Average 35.2%
Compared to 102 trail running shoes
Midsole softness soft to firm
0%
Heel stack brand
102%

Grip / Traction

Lug depth

Returning to the outsole, we once again used our vernier callipers to measure the lugs, which measured 3.5 mm.

Altra oz / 264g Lugs

The outsole features multiple cutouts to reduce overall rigidity, enhancing flexibility in all directions.

This is a standard design that provides solid performance across most terrains, though it doesn't specialise in any particular type. From our lab analysis and test runs, the MBC seems best suited for non-technical terrain and appears specifically designed for American ultras.

Altra oz / 264g Lug depth
Test results
oz / 264g 3.5 mm
Average 3.5 mm
Compared to 105 trail running shoes
Midsole softness soft to firm
1.7 mm
Lug depth
5.8 mm

Size and fit

Secondary foam softness

If you were hoping for a super-wide toebox, the oz / 264g might not meet your expectations. At 97.6 mm in the widest part of the upper, this shoe offers a width that is fairly typical, similar to most shoes on the market. However, there's a catch...

Altra oz / 264g Secondary foam softness
Test results
oz / 264g 97.6 mm
Average 98.8 mm
Compared to 105 trail running shoes
Midsole softness soft to firm
92.0 mm
Secondary foam softness
104.9 mm

Heel padding durability

The heel includes a reflective, horizontal finger-loop heel tab that not only adds a stylish touch, but we also found that significantly simplifies slipping your feet into the shoe.

Altra oz / 264g Heel padding durability
Test results
oz / 264g 86.3 mm
Average 78.9 mm
Compared to 67 trail running shoes
Midsole softness soft to firm
70.5 mm
Heel padding durability
92.1 mm

Midfoot feel

The heel padding is very exposed and appeared fragile from the first look, prompting us to brace for a disappointing performance in this area.

As it turned out, the Dremel test obliterated the heel padding, handing the MBC a dismal 1 out of 5 in this assessment. This result raises significant concerns about heel slippage and the shoe's durability, especially for those who tend to wear down this area with their Achilles.

Tongue: gusset type

We know that when someone invest £260 in a trail running shoe, it's normal to expect perfection down to the smallest detail, and happily, the oz / 264g meets these high expectations.

We were happy to find a fully gusseted tongue, which not only prevents unwanted movement while running at fast paces, but also keeps debris away from the toebox.

Altra oz / 264g Tongue: gusset type
Test results
oz / 264g Both sides (full)

Comfort

Tongue padding

The tongue of the MBC was a delightful surprise from the moment we first tried it on. At a glance, it appears remarkably thin, yet this is due to the padding being strategically positioned over the instep rather than throughout the entire tongue, as is common in most running shoes.

Altra oz / 264g eyelets

The lacing system performs well, though we noted the absence of an extra eyelet positioned nearer to the ankle, which would enhance the lockdown.

As a result, Altra has successfully added 5.3 mm of thickness to the tongue of the oz / 264g without noticeably increasing its weight. And it's a positive trade-off.

Altra oz / 264g Tongue padding
Test results
oz / 264g 5.3 mm
Average 6.4 mm
Compared to 105 trail running shoes
Midsole softness soft to firm
1.5 mm
Tongue padding
12.2 mm

Heel tab

The heel includes a reflective, horizontal finger-loop heel tab that not only adds a stylish touch, but we also found that significantly simplifies slipping your feet into the shoe.

Altra oz / 264g Heel tab
Test results
oz / 264g Finger loop

Removable insole

The insole of the Altra Mont Blanc is removable—a feature not typically seen in racing shoes. However, there's a catch—since Altra uses a very specific last, finding suitable off-the-shelf footbeds might be challenging.

Additionally, we discovered that this is a great outsole, featuring perforations for enhanced ventilation in warm conditions. Therefore, we believe it's wise to retain the original footbed unless absolutely necessary to replace it.

Altra oz / 264g Removable insole
Test results
oz / 264g Yes

Misc

Reflective elements

We absolutely love reflective elements on all shoes, and we consider them essential for trail shoes—especially those likely to be used in ultra marathons, where racing at night is common.

Test results
oz / 264g Yes