On Cloudboom Strike LS2 First Run: A Premium Carbon Racer With a Lot to Offer

Introduction

On’s premium carbon racing line has a new flagship, and early miles in Zurich suggest it is a genuinely interesting one. The Cloudboom Strike LS2 pairs a new helium HF midsole with a light spray upper, and On invited testers to run in them at OnHQ and speak with the founders and designers behind the shoe.

This is a first-run look rather than a long-term verdict, but there is already plenty to work with: two mixed-pace runs including a track session of 400m intervals, enough to get a feel for how the shoe behaves from easy miles through to beyond marathon pace.

Key Specs at a Glance

On has not given an official stack height, but the drop is 5mm. The official weight is 158g, and the price is $310 or £300, which places it among the priciest carbon road racing shoes available.

One important note for shoppers: alongside this light spray version, there is also a regular version of the shoe with the same midsole setup but a more traditional upper, so the fit and price trade-offs differ between the two.

Midsole, Plate, and Outsole

The midsole uses On’s helium HF foam, now claimed to be 15% lighter than the predecessor’s version. The interesting change is a new geometry On calls cloudtech sphere: two channels cut into the midsole that decouple the forefoot. The idea is that the foam can deform more, which in turn feeds back more energy.

Sandwiched between the dual-density helium HF foam layers is a curved carbon speedboard plate that is lighter and stiffer than previous versions. There is also a decent rocker to guide the foot through the stride.

Underneath, the outsole carries a generous covering of rubber for a carbon racing shoe, which is a practical touch for a shoe in this category.

Upper and Fit: Handle With Caution

Up top sits On’s light spray upper: a robot-sprayed, laceless, seamless, glueless one-piece construction. Technically there is no heel counter here, just a thicker section of light spray material at the heel, with very thin heel collars cut lower than the previous generation. Everything is integrated into a bootie-style setup.

Fit is the trickiest part of this shoe. In a regular UK 8.5 / US 9.5, which fits in most On shoes, the reviewer with high insteps found the previous Cloudboom Strike LS’s light spray uppers almost impossible to get on. This time, the shoe slid on noticeably more easily and positioned well once in place, though on a second morning it became more of a tussle again, possibly due to thicker socks.

Once on, the fit is snug, narrow, and secure, which suits a carbon racer: the foot is held firmly on the platform, which adds a sense of stability. Toe box clearance is just about adequate, with little flex up front, which is fairly classic for this category. The heel collar is snug with a steep sweep, and during fast cornering there was some slipping off the platform at the heel, a byproduct of having no traditional heel counter. If you need lots of rearfoot support, this may not be the shoe for you.

On the plus side, the low cuff no longer pinches across the midfoot the way the previous light spray model did. If you have high insteps, consider going half a size up to make entry easier, but keep in mind there is no lacing to dial the fit in afterwards, so any looseness is permanent. Fit here genuinely deserves caution.

Ride Feel: Smooth at Slow Pace, Punchy When Pushed

The standout early impression is how smooth the shoe feels. There is a nice rocker, and the midsole is soft yet springy with quick compression and return. Even at slow pace, the foam gives energy back and keeps legs feeling fresh.

When you push the pace, the shoe really comes to life with a punchy, poppy, lively ride. Compared with softer, bouncier foams that take more time to return, this foam is less compressive, more controlled, and returns with real impetus. The carbon speedboard plate levers you quickly into toe-off, and the transition through the gait cycle feels smooth and lively.

Notably, the ride is reliable underfoot rather than wild and wobbly. Landing mid to forefoot, rolling onto the rocker and out through toe-off is predictable and consistent, and the shoe actively helps drive energy forward rather than requiring you to control it. Comfort underfoot is smooth, soft, and protective, with enough cushioning in the forefoot.

How It Runs at Top Speed: Track Intervals

To test the shoe at its limit, a session of five 400m reps with 200m recovery jog, all in 77 seconds, showed the snappier foam responds well to track work. That is not true of all super shoes, where very soft foams can interact poorly with the unforgiving track surface.

For a sub-three marathon runner doing this kind of training, the shoe felt smooth, lively, and controlled. Engaging the forefoot and rolling off the rocker into a quick toe-off worked particularly well. Elite-level runners chasing a more grounded, stiffer track feel may still want alternatives, but for many, this shoe handles intervals impressively.

Is It Worth the Price?

At £300 or $310, this is a premium purchase, and the honest comparison question is still open. The reviewer considers it clearly not as good as the much more expensive Pro Evo 3, and is not fully convinced it beats the Fast R3, though it offers a slightly different ride character some runners will enjoy. Meta Speed Edge Tokyo may still be the personal favourite.

What is beyond doubt is that this is a shoe worth racing in. Some carbon racers never inspire that instinct, but this one sparks real interest in putting it to the test over a 10K, half marathon, or the marathon distance itself. A full review with more miles will follow.

Conclusion

The On Cloudboom Strike LS2 makes a strong early impression: a smooth, protective, and energetic ride with a snappier foam than many rivals, a plate that drives quick toe-off, and respectable reliability underfoot. The light spray upper works better than the previous generation for tricky insteps, but entry is still occasionally a struggle, the fit is snug and non-adjustable, and heel security is limited by the lack of a heel counter. If the fit works for your foot and you are willing to pay a premium, this is one of the more exciting carbon racers to race in this season.