On Cloudboom Strike Reviews

Worn for most of their workouts, at nearly all paces, and it felt comfortable and smooth. The thick foam insole makes the forefoot very bouncy, which suits 5K up to the half marathon; they are unsure about the end of a full marathon and think heel strikers will get less from it. Heel lockdown is weak, with some slipping and a worry about rubbing, and the very long laces came undone twice despite a double knot. The toe box is roomy and the outsole grips well.

100 miles in the shoe, including tempo runs, longer intervals and a 2K time trial. The bouncy midsole did not change over that distance and the outsole was only just starting to wear through. It is stiff with plenty of forefoot cushioning and works best from 10K upward. The narrow heel meant it was not quite stable enough for them past about 10 miles, so it suits neutral mechanics best, and low socks let the heel collar dig in.

Score 7.45. A true super racer and the missing piece in On's range. The thick insole/midsole gives high forefoot protection without losing reactivity. It suits a push-off, forefoot style and needs good running mechanics. The thin outsole rubber will likely wear first.

On's best race shoe yet: light (<8 oz), with Helion HF cushion right under the forefoot and grippy rubber. Sizing ran long by up to a full size, and the stiff heel collar dug into one tester's Achilles, leaving it unrunnable two days later. Wear crew socks. A Vaporfly 3 costs $100 less.