Fit

The On Cloudflash fits true to size. The achilles
pillows and soft foam in the heel really make the heel feel more
comfortable than is typical of a racing shoe. You sink in just enough to
feel a nice hug. The upper fits much better than the upper on the
Cloudboom. The tongue is still slippy, but not as much as the
Cloudboom’s tongue. That’s thanks to the more dialed-in fit of the
upper.

On’s racing shoes still badly need a gusseted tongue. I’m
hopeful those are coming in the next generation. The Cloudflash is much
more in line with On’s typical craftsmanship than the Cloudboom.

Support

The Cloudflash has a basic internal heel counter
but it’s not very stiff. Additionally, the Cloudflash features synthetic
suede internal reinforcement around the edges of the shoe from heel to
toe to keep you on top of the footbed. The internal reinforcement also
connects up to the front two lace holes to better support the forefoot
on tight turns.

Traction

The On Cloudflash comes with great traction. It’s
an odd addition to something so race focused. Usually, shoe companies
sacrifice traction so a racing shoe weighs less. The Cloudflash outsole
really grabs the ground using a multi-level repeating “x” pattern at the
heel and forefoot. It’s an ideal pattern for digging into a rubber
track during intervals.

Just like with the Cloudboom, the
outsole’s got some durability questions. The outsole’s forefoot lugs are
showing plenty of wear from my testing. I think you will most likely
get 200-250 road miles out of these but I can’t guarantee it. Using a
treadmill or track (outside of races) will help avoid extra wear from
pavement and extend the shoe’s lifespan. 

Materials

The upper of the Cloudflash is a single layer of
very nice engineered mesh with strategically placed fuse around the lace
loops for strength and on the heel for shape. The tongue is made of the
same synthetic suede from the Cloudboom and the New Balance FuelCell TC. As with all On shoes, the materials look nice, but there’s nothing here that other racing shoes aren’t already doing.

And while the single layer of engineered mesh makes the shoe feel incredibly light, it’s still heavier than the Nike Vaporfly Next%, the world’s current favorite racing shoe.