Due to the unique On Cloud system, we had to use a small review

The Due to the unique On Cloud system, we had to use a small.0 presents itself in the lab as an interesting choice for:

• On fans seeking a versatile daily trainer suitable for various paces and distances.
• Toebox width at the widest part.
• Runners with a narrow foot profile and a generous budget who value exceptional build quality.

On the other hand, perhaps you're drawn to the CF 4.0 for its low weight, yet desire a soft, cloud-like feel. Well, that's something this shoe doesn't provide based on our lab tests.

Thats a 29.2% increase, which, as weve seen before, outperforms most shoes on the market ASICS Novablast 3 or the Effective rockered geometry oz / 235g.

Due to the unique On Cloud system, we had to use a small hack to accurately measure the height at the official point specified by World Athletics. This is how we determined the 36.1 mm, indicating a substantial stack height beneath the heel.

Nonetheless, one shouldn't anticipate in this On the same amount of foam underfoot as seen in a standard midsole. The clouds invariably offer slightly less cushioning.

Fortunately, the forefoot aligned perfectly with a complete "cloud," so we didn't need to make any adjustments and simply conducted a standard measurement. We determined the result to be 28.2 mm, which is more than sufficient for any forefoot or midfoot striker.

On told us that the official drop was 8 mm, and after meticulously following the official WA guidelines, we measured an impressively close 7.9 mm.

Kudos to them for being one of the select brands with such precise and accurate drop statements.

While the midsole system is named "CloudTec," it surprisingly delivers a different experience from its name. Is crafted from two distinct Helion foams, and our durometer showed a softness of 28.3 HA for the main one.

However, this characteristic isn't necessarily negative. Contrary to the common belief that softer is better in running shoes, a firm midsole offers its own unique advantages such as enhanced stability, superior ground-feel, and foot muscle development.

The supplementary Helion foam, positioned closer to the foot, ranks among the firmest midsoles we've assessed in our lab (33.0 HA).

Again, this isn't necessarily a drawback for all, especially when paired with On's CloudTec system. However, it's important to note that this combination is best suited for individuals who prefer a firmer feel over softer foams.

We placed the shoe in the freezer for 20 minutes and then reevaluated its softness. This method allows us to observe the foam's behavior.

In the case of the primary Helion slab, it changed to 33.0 HA. Interestingly, this is the same measurement we recorded for the secondary foam at room temperature.

That's merely a 16.8% increase, an excellent outcome that aligns perfectly with our expectations for a premium shoe that retails at a premium price.

We clocked the insole thickness at 4.1 mm, a typical measurement for any daily trainer. Just an average approach by On.

The Cloudflow 4 treated us to a comfortable and expected medium-width fit with no hot spots or dead space.

Retrieving a gel mold of the shoe's interiors and measuring its dimensions with a caliper, we got a standard width of 95.2 mm between the big toe and the pinkie. Just a regular and predictable width for a D medium width shoe.

Even the narrower part of the shoe's toebox (near the big toe) proved to be on par with the category average at 73.9 mm. No radical tapering or toe cramping here.

The shoe's vertical space didn't pose any concerns either, even with its slightly below-average toebox height of 25.3 mm.

As we mentioned earlier, a firm midsole can transform a shoe into a stable one, and that's exactly what happens with the Cloudflow 4.0.

The Cloudflow platform's built-in stability, aided by the Speedboard plate and the rockered geometry, ensures that we keep our form even in the longest runs, all while providing a subtle, pleasing responsiveness.

The previously mentioned Speedboard plate is a crucial element contributing to the torsional rigidity of this shoe, which we have given a rating of 4/5.

The heel counter is quite flexible, earning a score of 2/5 from us. It appears that On aimed to craft a comfortable daily trainer, opting not to enhance stability by stiffening this area.

Individuals experiencing Achilles issues will surely appreciate this feature and the fact that the heel collar is greatly padded!

Next, we'll examine the dimensions of the midsole.

In the forefoot, we noticed On's distinctive narrow design, coming in at just 110.0 mm. 

Shifting our attention to the heel, we observed that On has been slightly more generous, offering a width of 89.7 mm. This approach ensures secure landings, even for heel strikers.

The Speedboard plate in the midsole makes the shoe quite rigid torsionally, as we explained before. However, it doesn't have the same effect longitudinally, which might be surprising to some.

In our lab's bend test, where we apply force until the shoe bends at a 90-degree angle, it only took 22.0N of force from us! This indicates that the plate doesn't make the shoe uncomfortable at all for walking or gym workouts.

We repeated the test after placing the shoe in the freezer for another 20 minutes, and it certainly became stiffer, as we needed to apply 28.4N of force this time.

That's a 29.2% increase, which, as we've seen before, outperforms most shoes on the market.

Weighing in at a mere 8.6 oz (245g), the Cloudflow 4.0 is a remarkably light shoe, even with its robust outsole.

This is an impressive 0.7 oz (20g) lighter than the Cloudflow 3.0.

Upon unboxing the Due to the unique On Cloud system, we had to use a small.0 in the lab, we immediately observed that On had incorporated many features into the upper from their premier marathon racer, the On Cloudboom Echo 3, Toebox width - widest part new method.

Add a shoe.

While not the top score that the high-priced, blazing-fast Echo 3 garnered, it's still a great result and ensures optimal ventilation for summer runs.

Next, we conducted the light test. Here, we discovered that the shoe didn't have visible ventilation holes. However, we observed that the transparency extended into the midfoot area, ensuring optimal ventilation for the entire foot.

Curious about how this On maintained good airflow without any visible ventilation holes, we turned to our microscope.

The crucial element for this upper is its minimal thickness. We believe that if it were slightly thicker, the ventilation would be severely compromised.

The absence of large ventilation holes often leads to impressive durability, as there are no weak points in the robust upper.

This is precisely the case with the Cloudflow 4.0, which we validated in our rigorous Dremel test. Not many shoes achieve such a fantastic 3/5 score!

Our enthusiasm soared after the initial test, but it quickly deflated during the subsequent Dremel evaluation.

In the heel test, the CF4 revealed its vulnerabilities, earning a disappointing score of just 2/5 from us.

As we continued to evaluate the outsole's durability, we found that the rubber was harder than the average shoe. We measured its hardness at 85.4 HC using our Shore C durometer in the lab.

This hardness aligned with what we expected from the Swiss brand. Given the shoe's design, it concentrates the runner's weight on a smaller surface area. The rubber simply needs to withstand more weight compared to most other shoes.

In our final test using the Dremel, the outsole took center stage. We discovered that, even though it's made of a harder rubber—which downgrades grip—the 1.0-mm indentation created is a disappointing outcome.

It's not extremely alarming, and the outsole is not going to fall apart after 200 miles, but we expect more from a daily training shoe.

The team at On is obviously experienced and conducts a huge series of tests before placing any shoe on the shelves.

That's probably why they've included a thicker-than-average rubber to offset potential durability issues. This approach is effective, but it comes with a trade-off: a slightly heavier shoe.

At a price of $160, we anticipated that On would include at least a couple of reflective strips on the shoe for safety during night runs. Unfortunately, we were disappointed to find... none.

The shoe's design is focused on being lightweight, and one easy way to achieve this is by reducing the padding in the tongue (2.5 mm).

Unfortunately, this approach can cause issues such as lace bite during long workouts. We believe a slightly padded option would have been more interesting, even if it added a few extra ounces.

The tongue features a bootie-style construction, a preferred choice for many of On's running shoes. And it effectively prevents unwanted movement during high-speed runs or frequent cornering.

The quest for weight savings presumably led to the omission of a cool heel tab.

The insole can be easily removed, but it's important to note that not all third-party insoles or over-the-counter orthotics may fit seamlessly inside the Cloudflow 4.0.

The shoe's design, characterized by a narrow body paired with a wide toe cap, could potentially limit compatibility with certain insoles.