Our verdict

The On Cloudflyer 4 stirred up a range of emotions within us. On the positive side, we encounter top-notch construction at a time when this seems to be a waning quality among most brands. Furthermore, it offers us a stable and enjoyable ride. However, the flip side is its potentially steep price for beginners, who are indeed the main target group for this shoe. It's also too heavy and features an unconventional lacing system that could be frustrating for some.

Pros

  • Superb construction quality
  • Accommodates broad feet well
  • Flexible and comfortable
  • Stable ride
  • A rockered design that works
  • Doubles as a walking or gym shoe
  • Good airflow

Cons

  • Could be lighter
  • Pricier compared to other daily trainers
  • Weird lacing system

Audience verdict

83
Good!

Who should buy

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

  • 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 £180, it's one of the priciest daily trainers on the market.

On Cloudflyer 4

Who should NOT buy

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 ASICS Novablast 3, which is also way lighter.

Similarly, this shoe might not be the best fit for those on a budget. Priced at £180, 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.

On Cloudflyer 4

Breathability

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.

On Cloudflyer 4 microscope

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

On Cloudflyer 4 micro2

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.

Test results
Cloudflyer 4 4
Average 3.8
Compared to 221 running shoes
Number of shoes
1
Breathability
5

Durability

Toebox durability

After seeing how well the On Cloudswift 3 held up, we thought this shoe would be great for solid durability.

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

On Cloudflyer 4 Toebox durability
Test results
Cloudflyer 4 1
Average 2.3
Compared to 155 running shoes
Number of shoes
1
Toebox durability
5

Heel padding durability

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.

On Cloudflyer 4 Heel padding durability
Test results
Cloudflyer 4 1
Average 3.2
Compared to 151 running shoes
Number of shoes
1
Heel padding durability
5

Outsole hardness

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

On Cloudflyer 4 outsole

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

On Cloudflyer 4 Outsole hardness
Test results
Cloudflyer 4 85.0 HC
Average 80.4 HC
We use an average of four tests. The photo shows one of those tests.
Compared to 272 running shoes
Number of shoes
54.9 HC
Outsole hardness
92.8 HC

Outsole durability

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.

On Cloudflyer 4 Outsole durability
Test results
Cloudflyer 4 1.2 mm
Average 0.9 mm
Compared to 133 running shoes
Number of shoes
0.0 mm
Outsole wear
2.0 mm

Outsole thickness

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.

On Cloudflyer 4 Outsole thickness
Test results
Cloudflyer 4 2.9 mm
Average 3.2 mm
Compared to 291 running shoes
Number of shoes
0.0 mm
Outsole thickness
6.6 mm

Weight

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 ASICS Novablast 3.

On Cloudflyer 4 Weight
Test results
Cloudflyer 4 10.86 oz (308g)
Average 9.38 oz (266g)
Compared to 292 running shoes
Number of shoes
5.26 oz (149g)
Weight
12.56 oz (356g)

Cushioning

Heel stack

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.

On Cloudflyer 4 Heel stack
Test results
Cloudflyer 4 33.3 mm
Average 33.6 mm
Compared to 291 running shoes
Number of shoes
7.6 mm
Heel stack
42.7 mm

Forefoot stack

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.

On Cloudflyer 4 Forefoot stack
Test results
Cloudflyer 4 23.5 mm
Average 24.9 mm
Compared to 291 running shoes
Number of shoes
7.6 mm
Forefoot stack
35.8 mm

Drop

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

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

On Cloudflyer 4 Drop
Test results
Cloudflyer 4 9.8 mm
Average 8.7 mm
Compared to 291 running shoes
Number of shoes
-0.8 mm
Drop
16.1 mm

Insole thickness

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.

On Cloudflyer 4 Insole thickness
Test results
Cloudflyer 4 4.2 mm
Average 4.5 mm
Compared to 287 running shoes
Number of shoes
1.5 mm
Insole thickness
7.3 mm

Midsole softness

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

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.

On Cloudflyer 4 Midsole softness
Test results
Cloudflyer 4 31.6 HA
Average 21.4 HA
We use an average of four tests. The photo shows one of those tests.
Compared to 219 running shoes
Number of shoes
8.5 HA
Midsole softness (soft to firm)
41.5 HA

Secondary foam softness

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

On Cloudflyer 4 Secondary foam softness
Test results
Cloudflyer 4 25.3 HA
Average 25.2 HA
We use an average of four tests. The photo shows one of those tests.

Midsole softness in cold

Note: a low durometer measurement equals a soft material, whereas a high measurement means it's firm.
On Cloudflyer 4 Midsole softness in cold

Difference in midsole softness in cold

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.

On Cloudflyer 4 Midsole softness in cold
Test results
Cloudflyer 4 23.3%
Average 25.6%
Compared to 218 running shoes
Number of shoes
0%
Difference in midsole softness in cold
100%

Stability

Lateral stability test

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.

Torsional rigidity

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. 

Upon twisting the shoe, we decided on a fair score of 3 out of 5.

Test results
Cloudflyer 4 3
Average 3.2
Compared to 270 running shoes
Number of shoes
1
Torsional rigidity
5

Heel counter stiffness

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

On Cloudflyer 4 heel

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

Test results
Cloudflyer 4 3
Average 2.8
Compared to 254 running shoes
Number of shoes
1
Heel counter stiffness
5

Midsole width in the forefoot

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

Measuring at 116.3 mm, it outshines the width of nearly every other running shoe.

On Cloudflyer 4 Midsole width in the forefoot
Test results
Cloudflyer 4 116.3 mm
Average 113.6 mm
Compared to 292 running shoes
Number of shoes
100.5 mm
Midsole width in the forefoot
126.5 mm

Midsole width in the heel

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.

On Cloudflyer 4 Midsole width in the heel
Test results
Cloudflyer 4 90.3 mm
Average 90.5 mm
Compared to 292 running shoes
Number of shoes
74.9 mm
Midsole width in the heel
106.6 mm

Flexibility

Stiffness

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...

Test results
Cloudflyer 4 15.4N
Average 29.3N
We use an average of four tests. The video shows one of those tests.
Compared to 274 running shoes
Number of shoes
2.2N
Stiffness
94.4N

Difference in stiffness in cold

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.

Test results
Cloudflyer 4 25.9%
Average 36.3%
Compared to 274 running shoes
Number of shoes
0%
Difference in stiffness in cold
148%

Size and fit

Internal length

The shoe runs just a bit longer than expected, but it's not substantial enough to suggest sizing up. The shoe measures 265.7 mm, which is only a slight deviation of 0.7 mm from the expected 265.0 mm for a US size 9.

On Cloudflyer 4 Internal length
Test results
Cloudflyer 4 265.7 mm
Average 269.1 mm
Compared to 155 running shoes
Number of shoes
259.9 mm
Internal length
280.4 mm

Toebox width at the widest part

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

On Cloudflyer 4 pov

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.

On Cloudflyer 4 Toebox width at the widest part
Test results
Cloudflyer 4 97.3 mm
Average 98.3 mm
Compared to 292 running shoes
Number of shoes
89.5 mm
Toebox width at the widest part
109.1 mm

Toebox width at the big toe

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.

On Cloudflyer 4 Toebox width at the big toe
Test results
Cloudflyer 4 80.3 mm
Average 78.0 mm
Compared to 166 running shoes
Number of shoes
60.4 mm
Toebox width at the big toe
92.5 mm

Tongue: gusset type

Although we were a bit disappointed to find a non-gusseted tongue on a £180 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.

On Cloudflyer 4 Tongue: gusset type
Test results
Cloudflyer 4 None

Comfort

Tongue padding

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.

If the upper were narrower, however, this thick tongue could potentially create problems.

On Cloudflyer 4 Tongue padding
Test results
Cloudflyer 4 10.6 mm
Average 5.6 mm
Compared to 289 running shoes
Number of shoes
0.5 mm
Tongue padding
14.2 mm

Removable insole

We encountered absolutely no issues when removing the insole.

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

On Cloudflyer 4 Removable insole
Test results
Cloudflyer 4 Yes

Misc

Reflective elements

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 Cloudflyer 4 Reflective elements
Test results
Cloudflyer 4 Yes