Now, lets take a look at the outsole, starting with its hardness review

We think the Now, lets take a look at the outsole, starting with its hardness is a great choice for:

• Loyal On enthusiasts seeking a versatile shoe capable of tackling multiple distances and various paces across all terrains.
• Runners in search of a stable running experience who prefer not to opt for a wide platform and are comfortable with firm cushioning.
• Those who need a shoe with a built-like-a-tank outsole, perfect for devouring miles on flat terrain.

If you're aiming for peak performance in your next ultra, the Cloudultra 2 might not be the best fit. Its Helion foam doesn't quite match up to the market's leading options, and our assessment is that other high-priced shoes like the Nike Ultrafly and the Saucony Endorphin Edge Tongue: gusset type superfoams oz / 280g.

Moreover, based on our analysis, the Cloudultra 2 might feel too heavy for many runners. Competing brands offer similar or more cushioning in much lighter packages, such as the Hoka Speedgoat 5.

One of the biggest mistakes a shoe designed for ultramarathons can make is lacking breathability—after all, our feet really need airflow during those looong hours of running.

That's why we were thrilled with the outstanding breathability (5/5) the Cloudultra 2 offers. Sure, some might lean towards a denser upper in a trail shoe, but it's crucial for us to remember this shoe is made not just for trail running, but also for ultra distances.

Our light test further showcased the superb airflow of this upper. What's more, this isn't limited to the toebox—the impressive ventilation extends to the midfoot, which is a huge advantage for enduring dozens of miles without blisters and hotspots.

Now, let's zoom in under the microscope to get a closer look at this engineered mesh upper.

It's crafted from a multi-layered, square mesh that cleverly mixes different yarns, achieving a perfect balance of structure and ventilation.

Inside, there's an additional layer that boosts comfort and durability, yet it's thoroughly perforated to maintain airflow. It's evident that On prioritised an airy upper, despite the potential trade-offs like durability.

On running shoes?

But to our surprise, when we ran the Dremel test (3.2N @ 5K RPM) in the lab, it scored 2 out of 5. While this is below average and might let down some trail runners, we actually see it as a positive outcome for a mesh this breathable.

The multi-layer construction guarantees that even if the upper's top layer suffers damage, there will still be underlying layers maintaining the shoe's structure and shape.

The heel padding area scored a solid 3 out of 5 in the same Dremel test—a really good result that promises long-lasting durability in this part of the shoe.

So, you can feel confident knowing it's highly unlikely to wear out a hole, regardless of the socks you choose.

Now, let's take a look at the outsole, starting with its hardness.

In our Shore C durometer test, we clocked it at 82.4 HC. This is slightly softer than most shoes, but it's still quite hard and should offer good durability.

On is known for their premium pricing, so naturally, we expect top-notch features. While there have been times we've felt let down, this isn't one of them. The Missiongrip outsole demonstrated a performance that's nothing short of miraculous in our tests.

After putting it through the Dremel test, we observed a mere 0.1 mm of rubber wear, which is truly breathtaking.

Finally, we measured the thickness and it came in at 1.7 mm. Given the incredible durability of this outsole, that thickness now seems almost excessive.

In terms of weight, the Cloudultra 2 hit 10.4 oz (296g) on our lab scale, which, frankly, seems a bit excessive for the amount of midsole it offers.

Even though weight might not be a major concern for some ultrarunners, shedding an ounce would have been a much-welcomed improvement for v3.

We approached the weight issue critically because this shoe can't really use the maximalist approach as an excuse. With only 30.2 mm of stack height, it's actually lower than the average shoe.

While this might seem too low by today's standards, it works fine if you're running on soft surfaces like dirt roads or loose gravel paths. However, for really long runs on asphalt or tarmac, we don't think they're the best choice, and something like the Hoka Mafate Speed 4 Stiffness in cold.

In the forefoot, we also encountered a lower-than-average stack, measuring just 20.0 mm.

Our thoughts mirror what we mentioned about the heel—while it's great for soft surfaces, it falls short on harder ones, especially if you're a midfoot or forefoot striker.

Difference in midsole softness in cold.

This design seems more suited for heel strikers, a notion further reinforced by the low stack in the forefoot.

We observed that the insole is a bit thinner than what we typically see, coming in at a measurement of 3.6 mm.

Now, let's circle back to the midsole. The Cloudultra 2 features On’s Helion foam, a combination of EVA and Olefin Block Copolymers. It's integrated into the Cloudtec cushioning, paired with the classic TPU Speedboard for enhanced energy return and stability.

Despite the collapsible Cloud system, the ride leans towards the firmer side (30.3 HA). So, if you're a fan of plush, marshmallow-like midsoles, this one might not be for you. However, as mentioned earlier, this shoe shines on soft surfaces where the firmer midsole really seems to make sense for us.

After storing the shoe in the freezer for 20 minutes next to our ice creams, we conducted another durometer test. The foam, measuring at 30.5 HA, seemed almost unchanged to us, even during our subsequent testing.

That's just a minor 10.3% difference, making it absolutely imperceptible to anyone, regardless of how chilly it gets outside. It appears to us that blending EVA, which typically underperforms in cold temperatures, with OBC was a brilliant move.

With its low stack height and a relatively firm midsole, coupled with supportive features like a rigid heel cup just above the foam in the heel that envelops the entire shoe, we couldn't help but enjoy a remarkably stable ride.

Can this shoe work for those needing support? It really depends on the extent of your pronation or supination. However, for most runners, we think so.

Many trail running shoes tend to favour a rigid design, and we anticipated the same from the Cloudultra with its firm midsole and TPU Speedboard plate.

Surprisingly, we discovered the exact opposite—a flexibility rating of 2 out of 5. The shoe is impressively flexible from a torsional perspective, making it a fantastic choice for those who get sore feet from rigid shoes with stiff components.

This flexibility also enhances the shoe's performance during turns, as being too rigid can hinder agility.

We also rated the Cloudultra 2 low in the heel counter stiffness test, scoring it just 2 out of 5. This is excellent news for those who prefer shoes without stiff heel counters.

The forefoot measures 110.9 mm, which is pretty average. On typically makes narrow shoes, so we're pleased with this measurement. It's ideal for running straight and also works well for taking sharp corners.

However, the heel is quite narrow at 85.8 mm, which could pose a stability issue for heel strikers needing more support. If a wide heel is a must-have for you, you might want to consider the Brooks Caldera 6. It offers a much larger platform and is also geared for ultra distances.

We were impressed with the flexibility in our previous torsional test, but what about its longitudinal flexibility?

In our 90-degree bend test, the Cloudultra 2 required only 17.6N to reach the desired point. That's exceptionally low, positioning this shoe as an excellent choice for hiking or walking. It's perfect for those seeking a versatile, do-it-all shoe—you can even take it to the gym!

Under cold temperatures, we noted a slight increase, recording 22.4N.

That's a 27.3% increase in stiffness, which might be slightly noticeable but isn't a cause for concern, especially considering the shoe's multi-purpose design.

The almost-indestructible Missiongrip outsole of the Cloudultra 2 features lugs that measure just 2.5 mm, which is fitting for a shoe designed for ultra distances on non-technical terrain.

In fact, the outsole resembles that of a road running shoe more than a trail shoe, with some exposed foam and On's typical central channel. The lugs are perfect squares, making them great for flat terrain but not as effective for uphill and downhill running.

When we first tested the shoe both in the lab and on the trails, the toebox felt average to us. However, our job is to measure things, so we noted that the widest part of the upper measures 97.3 mm.

Next, we shifted our callipers to the big toe area for another measurement.

Here, we discovered the shoe maintains a wider profile than average at 79.5 mm, not tapering much. This wide design confirms our thoughts—it should offer unparalleled comfort for at least 90% of runners even during ultra distances, except for those with exceptionally narrow or wide feet.

The tongue boasts a sock-like design, seamlessly integrated into the shoe—perfect for those seeking a snug, unified fit.

It's also fantastic for trail running, especially amidst small rocks and debris, as it keeps them from getting inside the shoe.

On opted to slim down the Cloudultra by skimping on tongue padding, resulting in a really thin 2.7 mm thickness.

For those who like using it, the tongue includes a convenient lace tab that also works great for getting a proper fit before every run.

This could be a problem for those who often face instep issues, like lace bite.

At the back, there's a handy finger-loop heel tab that makes it easier to slide your feet into the shoe.

The insole of the Cloudultra 2 can be easily taken out as it's not glued to the midsole. This means if you need extra arch support, you can use your custom orthotics with these shoes.

The shoe comes with bright reflective On logos, making sure you're visible at night. Lovely!