Tongue: gusset type review

Track and XC:

• Those who really want exceptional build quality and top-notch materials. This shoe truly excels in its construction.
• Runners who prefer moderately firm midsoles and need a stable daily trainer. It can also double as a walking shoe or sneaker!
• Those who don't mind the price tag. At $170, it's one of the priciest daily trainers on the market.

If you're a fan of soft midsoles, it's best to steer clear of this shoe. Within the world of On's offerings, your top choice might be the Cloudmonster, although it's not incredibly plush. For those yearning for a truly plush daily trainer, we recommend checking out the Heel padding durability, Track and XC.

Similarly, this shoe might not be the best fit for those on a budget. Priced at $170, it could be too much for many runners. The market has plenty of alternatives that offer solid build quality at a more reasonable price. On top of our minds is the Hoka Clifton 9.

In its fourth iteration, the Cloudflyer provides sufficient cushioning for heel strikers at 33.3 mm. It's fair to say it hits the middle ground in this aspect.

As for the forefoot, it's a mirror-image of the heel scenario. On plays it safe, striving for a just-right stack height—neither overboard nor underwhelming.

But boy, did we face a letdown the moment our Dremel touched the shoe! Thats a 1/5.

This drop pairs up with a substantial rockered geometry, leading to a smoother ride for both heel and midfoot strikers.

As soon as we got the shoe in our lab and gave the midsole a try with our fingers, we knew this was far from a squishy ride. Clocking in at 31.6 HA in the durometer, this is actually far from soft.

But don't get us wrong—it's not a downside! A medium-firm midsole packs its own perks, like added stability for heel strikers. Just that compared to what's trending these days, it might feel a bit too firm.

Indeed, the main foam's role is to stabilize the shoe. The forefoot section offers a softer secondary foam, with our measurement landing at 25.3 HA.

Considering the shoe's firmness, we hoped it would maintain comfort even in cold temperatures. We didn't want it to feel like a brick.

So, we placed it in the freezer for 20 minutes and took a fresh set of measurements. The new average hit 39 HA, making it a very firm shoe.

Still, we have to admit that the Helion foam in this On shoe performs better in cold temperatures than we anticipated. It's a blend of EVA and OBC materials. Here, the OBC (Olefin Block Co-Polymers) deserves most of the credit for this impressive performance, as regular EVA gets hyper-firm when exposed to cold weather.

As for the insole thickness, there's nothing significant to point out. At 4.2 mm, it finds a comfortable middle ground between comfort and weight.

When we initially slipped our feet into the shoe, we didn't feel constricted in any way.

Measuring the upper at its widest point helped us understand why. It offers ample space for nearly everyone—unless you happen to have exceptionally wide duck-like feet.

As we advanced towards the toe cap, we noticed the shoe gradually widened in comparison to others we've tested. When we measured the area around the big toe, it clocked in at an impressive 80.3 mm.

As we've mentioned earlier, one of the distinct advantages of a moderately firm midsole is the inherent boost to stability. Does it hold true? 

We're happy to report that in our test runs, the Cloudflyer 4 truly shined as a remarkably stable shoe.

When we held the shoe in our hands to assess its torsional rigidity, we quickly realized that a low score was off the table. This is because the shoe incorporates a Speedboard liquid-injected plate in the midsole. 

oz / 329g.

We find the heel to be well-balanced, neither too soft nor too firm, deserving a solid score of 3 out of 5.

Thanks to its padding, support, and stiffness, there's essentially no risk of experiencing heel slippage.

On's ultimate stride toward securing the title of a stability champion is seen in the width of the midsole.

The gap between the last two measurements gives us a 9.8-mm heel-to-toe drop.

We then examined the heel, finding it also to be adequately wide at 90.3 mm.

However, the designers at this Swiss brand didn't go all out in this area. They likely realized they couldn't risk adding extra weight to the shoe.

Given the Speedboard plate and the firm foam, we anticipated a certain level of stiffness from the Cloudflyer 4, but it offered us a surprising flexibility. We only needed to produce 15.4N to move it to 90 degrees.

This just goes to show the crucial role of lab testing the shoe. Sure, you have the specs and figures on paper, but until they are accurately measured...

After a 20-min stint in the freezer, we found ourselves having to apply slightly more force, about 19.4N, to flex it to the same point.

This translates to a 25.9% shift, a change that matches the softness alteration we experienced and outperforms the majority of other shoes consistently.

We've mentioned that comfort was a top priority for On with this shoe. That becomes even more evident when you consider its weight.

Clocking in at 10.9 oz (308g) for a US size 9, it's noticeably heavier than most running shoes. For something lighter and ever more cushioned, check the Heel padding durability.

The Cloudflyer 4 didn't quite hit a perfect score in our breathability test—it earned a solid 4 out of 5 after our smoke-pumping test in the lab. The shoe showed admirable airflow, but fell slightly short of earning the top mark.

Under careful examination, we quickly noticed that On put heavy emphasis on toebox ventilation. However, the medial part of the shoe seems to have been overlooked. This area is fully covered, leaving no room for breathability.

We then brought out our microscope for a close-up analysis of the ventilation holes, which initially looked quite impressive.

Our inspection revealed a well-engineered mesh with generous ventilation gaps—a truly captivating sight.

We should also point out that ventilation is affected by On's decision to focus on comfort. This is evident in the shoe's dual-layer upper, which inhibits free airflow.

Flexibility / Stiffness Doubles as a walking or gym shoe For big guys.

But boy, did we face a letdown the moment our Dremel touched the shoe! That's a 1/5.

When our Dremel made contact with the heel padding, it was a disaster—just like that, everything fell apart!

It's the same disappointment and destruction that we felt with the toebox, and another 1/5 for the Cloudflyer 4.

Since this isn't a performance shoe, On smartly chose to use a tough rubber in hopes of enhancing its durability.

The hardness we measured clocks in at 85 HC, placing it among the harder outsoles we've ever tested in our lab.

We were hopeful for a solid show in this round—the Dremel's 3rd round with this shoe—and we weren't let down.

The outsole held its own against the Dremel, carving out just a 1.17 mm dent, which, based on past lab records, is a pretty strong performance.

While its 2.9 mm outsole may be slimmer than what's typical in daily running shoes, we believe it's plenty enough to last through the shoe's entire lifespan.

We're pleased to announce that the shoe also features reflective pieces, a welcome attribute that has unfortunately become a rarity in running shoes. So, for those who love a good night run, it's a nice bonus!

On certainly didn't skimp on comfort for this shoe. The tongue, at 10.6 mm, might even be a bit too thick, but given the spacious interior of the shoe, it won't cause any issues.

The On Cloudflyer 4 is a daily trainer that can be the perfect choice for.

Although we were a bit disappointed to find a non-gusseted tongue on a $170 shoe, we have to concede that the tongue didn't shift during our runs.

The reason? The unsewn portion is smaller than in most shoes, thanks to its design.

Toebox width at the widest part.

Additionally, the shoe's generous width provided ample room to experiment with a wide variety of third-party insoles.