On Cloudboom Strike 2 Review: The Robot-Sprayed Racer

There are two versions and the difference matters. The standard On Cloudboom Strike 2 uses a conventional engineered mesh upper and weighs in around 191 g. The LightSpray Cloudboom Strike 2 replaces that with a seamless one-piece upper sprayed on by a robot arm in roughly three minutes, dropping the total to about 158 g and putting it among the lightest super shoes on sale anywhere. Both share the same midsole, plate and outsole. Both went on sale on the same day, with the LightSpray version sitting a clear tier above on price. Availability across Europe is broad rather than limited, which is a change from On's earlier LightSpray experiments, and the Swiss brand now has the manufacturing capacity to make the sprayed uppers in volume.

Published and independently reported figures for the road racer:

• Weight: roughly 191 g for the standard build; about 158 g for the LightSpray version
• Stack height: 40 mm heel, 35 mm forefoot
• Drop: 5 mm
• Support: neutral
• Midsole: Helion HF, a hyper foam On states is around 15 per cent lighter than the compound in the original Cloudboom Strike
• Midsole geometry: CloudTec Sphere — two channels through the forefoot and midfoot, plus a third central channel visible on the outsole
• Plate: curved carbon Speedboard, lighter and stiffer than the previous generation
• Upper: engineered mesh, or a laceless sprayed one-piece on the LightSpray model
• Intended use: half marathon and marathon racing, plus sharp workout days

The original Cloudboom Strike used On's signature hollow cloud pods, which compress vertically and then run out of travel. On the On Cloudboom Strike 2, the midsole is cut through with channels instead, so the foam can deform in multiple directions on impact and spring back from more of them. In practice that is On trying to solve the classic super-shoe compromise: a plate stiff enough to propel you tends to make a shoe feel harsh, while foam soft enough to protect you tends to feel vague. Splitting the job between a stiffer, lighter Speedboard and a foam that can move sideways is a neat structural answer. The weight saving is the visible result — around 15 per cent off the midsole compared with the shoe it replaces.

Weight, first. Even the standard mesh version undercuts most carbon racers, and the LightSpray build competes with shoes that cost considerably more and come in a fraction of the sizes. The 5 mm drop and 40 mm heel put it in the sweet spot most European road racers now expect: high enough to protect the legs deep into a marathon, low enough not to feel like stilts. Reviewers consistently note that the ride is firmer and more direct than On's daily trainers, which is exactly right for a race shoe — the brand's training models have long been criticised for feeling stiff, and here that character finally fits the brief. The sprayed upper also solves lockdown without pressure points, because there are no seams or overlays to dig in.

This is a narrow-purpose shoe with a narrow-purpose price. The LightSpray version in particular is a laceless, unadjustable upper: if the shape suits your foot it is superb, and if it does not there is no lace pattern to rescue you, so trying before buying matters more than usual. The sprayed construction is also porous by design, which is a virtue in July and a liability on a wet November morning in northern Europe. More generally, On still lacks the depth of road racing feedback that ASICS, Nike and adidas have accumulated over multiple generations, so long-term durability data is thinner. And as with every carbon racer, mileage is limited — this is not a shoe to train in.

Buy the On Cloudboom Strike 2 if you want a modern 40 mm carbon racer that weighs less than almost anything else on a European shop wall, and you like a firm, direct ride rather than a squashy one. Buy the LightSpray version if weight is the whole argument and you have confirmed the fit in person. Skip it if you need a wide fit or a heavily adjustable upper, if most of your racing happens in cold, wet conditions where a porous sprayed upper is a disadvantage, or if you want one shoe that covers training and racing. Runners who find On's Helion foams too firm generally do not change their minds here.

Within On, the Cloudmonster 3 Hyper is the shoe to buy if you want Helion HF underfoot every day rather than on race day, with a much taller 43 mm heel and no plate. The Cloudsurfer 2 remains the softer, more forgiving daily option. Outside On, the adidas Adizero Adios Pro Evo 3 is the extreme answer at under 100 g, though it is narrow, fragile and hard to buy. The adidas Adizero Adios Pro 4 is the more sensible carbon marathon shoe with a plusher midsole, while the ASICS Metaspeed Sky Tokyo offers similar weight with a wide option for feet the On shape does not suit.