On Cloudboom Max First Look: A Marathon Shoe That Feels More Super Trainer Than Race Day Rocket

Introduction

On has built the Cloudboom Max with a specific runner in mind: the 4 to 4.5-hour marathoner rather than the seasoned racer. With a price of £220 or $230, a weight of 283g (10 oz) for men in a US size 8, and an 8mm drop, it sits somewhere between a dedicated race shoe and a supportive daily trainer. After a first run, the clearest takeaway is that it behaves much more like a super trainer than a carbon plate race shoe.

That framing matters, because judging this shoe as a race-day weapon leads to disappointment, while judging it as a stable, cushioned cruiser paints a fairer picture.

Fit and Sizing: Consider Going Up Half a Size

The first thing worth knowing about the Cloudboom Max is the fit. The forefoot and midfoot offer plenty of room, the lockdown is secure once laced, and the padding around the heel and tongue feels comfortable despite being relatively minimal. However, the toe box length is the weak point. The shoe pushes the foot forward, and the big toe can press against the end of the shoe during the run, causing noticeable rubbing.

The practical recommendation from the first run is simple: go up half a size. Everything else about the fit was described as pretty good, so sizing appears to be the main adjustment needed before this shoe settles in.

Construction: Max-Stack Midsole and Speedboard

The midsole uses a dual layer of Helion HF hyperfoam intended to balance softness and responsiveness for the full marathon distance, with more support and cushioning than many elite-focused super shoes. A glass fibre infused speedboard and updated geometry are designed to improve efficiency for runners targeting that 4 to 4.5-hour window.

On top of that sits a light, breathable mesh upper that molds to the foot over long distances, plus a generous rubber outsole for grip and protection of the midsole foam. The overall build is clearly aimed at durability and support rather than stripping every gram away.

Ride Impressions: Comfortable at Marathon Pace, Clunky When Pushed

On a first 10k run at 5:00/km, described as an easy pace and roughly the pace the shoe targets for the marathon, the Cloudboom Max felt comfortable and easy to cruise in. The midsole is on the firmer side, but at that pace it held a nice, consistent rhythm.

Picking the pace up to around 4:30/km told a different story. The shoe did not feel like it wanted to go faster, and the extra weight is noticeable on foot. It never felt nippy, and the energy return from the midsole was modest. Instead, it felt sturdy, solid, and supportive.

The closest comparison in feel is something like the Superblast 2 or Megablast: a bigger, chunkier shoe that sits solidly on the foot. It is not a shoe for racing flat-out, but it excels at holding a steady pace over long distances, which is exactly what the target runner needs on marathon day.

Where It Fits: Super Trainer, Not Carbon Racer

Because of the firmer, supportive midsole, the Cloudboom Max offers far more stability than a minimal carbon plate race shoe. For runners chasing a 4 to 4.5-hour marathon who genuinely value stability, that could be a real benefit. Plenty of runners at that pace are happy in carbon racers, though, so stability is a preference rather than a requirement.

This is also where the shoe’s positioning gets tricky. At £220 in the UK, there are solid alternatives that deliver many of the same benefits for less. The Saucony Endorphin Speed 5 is cheaper and offers good stability, and the Megablast is only slightly cheaper while delivering a similar steady, supportive ride. Neither is as max-stack as the Cloudboom Max, but both cover much of the same ground.

Outsole and Grip

The outsole features a fairly thick layer of rubber that performed well on the first run. It was raining during testing, and there were no grip problems at any point. It also looks well placed to protect the midsole foam over high mileage.

Buying Advice

Buy the Cloudboom Max if you are a 4 to 4.5-hour marathon runner who wants a stable, supportive, max-stack shoe and you are happy to pay for On’s specific ride character. Go up half a size, and treat it as a super trainer rather than a race shoe. If you mainly want speed, or you already run comfortably in carbon plate racers, cheaper options with similar stability may serve you better.

Conclusion

The Cloudboom Max is comfortable, stable, and capable of holding a consistent marathon pace, but it is heavy for its class and not built to pick up the pace. Viewed as a carbon plate race shoe, it underwhelms; viewed as a supportive super trainer for mid-pack marathon runners, it makes a lot more sense. Expect it to be a shoe defined by its positioning, with fit and firmness being the two things to check before buying.