We may earn commission from links on this page, but we only recommend products we back: The Carbon X is for Hoka devotees who want an aggressive yet cushioned shoe for speed work and races.
- A carbon fiber plate embedded in the midsole guides you through your stride and helps you generate a forceful toe-off
- The foam below the carbon plate is rubberized EVA that also serves as the outsole; above the plate, soft EVA foam provides cushioning
- The heel-toe transition is rapid and can feel too aggressive for some runners; others find it smooth and propulsive
Price: $180
Type: Road
Weight: 8.7 oz (men’s) 7.1 oz (women’s)
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The Hoka One One Carbon X snagged the 50-mile world record three days after it was announced, but despite the accomplishment, it’s curiously difficult to nail down what this shoe is designed to do. Ultrarunners like Jim Walmsley, who broke the record earlier this month, don’t spend a lot of time racing on pavement. The shoe’s rubberized foam outsole isn’t made for trails, and it’s arguably too heavy to be a true road racer, although that doesn’t mean Hoka’s elite distance runners won’t adopt it for upcoming marathons in Berlin and Chicago. The carbon plate is designed to make it propulsive—it “minimizes deceleration and maximizes acceleration,” Hoka’s Footwear Design Director Matthew Head, Ph.D. told Runner’s World—but unlike a certain competitor, there’s no claim of how much or even whether the shoe makes you faster.
None of this means the Carbon X is a bad shoe, it’s just worth questioning the type of runner that Hoka is targeting for its $180 proposition. We’re not sure, so here’s how it feels: The early-stage Meta-Rocker puts the pivot point just behind the ball of your foot. Most Hoka shoes have this design, but what’s unfamiliar is how aggressively the shoe shoves you onto the forefoot. The carbon fiber plate is designed to hold the rocker’s shape throughout your gait cycle, Head says, and that expedites the heel-to-toe roll. Without additional heel foam (the offset is Hoka’s characteristic 5mm) the transition bothered our resident heel strikers, who felt their lower legs were expending extra effort to keep up. As a midfoot striker, I like the rocker’s positioning and stiffness, but we seldom encounter a shoe that so divides testers by our respective footstrikes.
Making a Fast Hoka
Outwardly, the Carbon X is a classic Hoka shoe. Cushioning is abundant. The respective heel-toe stack heights are 32mm and 27mm for the men’s shoe and 30mm and 25mm for the women’s model. Other Hoka models use Profly cushioning, in which the heel is softer than the forefoot. By contrast, this shoe’s Profly X cushioning stays consistent throughout the length of the shoe. The thick blue foam atop the carbon plate is a soft EVA compound and the lower white foam is a tougher, rubberized EVA material. “You don't feel the plate underneath, which is a plus, and you do get a little boost from the shape of the plate with every step,” said Runner’s World Video Producer Derek Call. “But as a heel striker, it feels like you put in too much work to get the desired effect when running at speed. After a 2-mile tempo run, my calves and shins felt as if I’d just PR’d in a half-marathon.”
A Minimal Upper
The single-layer engineered mesh upper feels light and airy. The tongue does a good job of distributing lace pressure, so a lock-down fit isn’t uncomfortable. To save weight, Hoka uses embroidery to shape the heel cup. It’s not ultra-supportive but it does the job; after some eyelet fiddling, I found a comfortable yet secure fit that kept my heel from lifting off the footbed, which doesn’t happen on every shoe. The heel pull tab is a nice touch, too.
Should You Buy the Carbon X?
To say that a shoe is good for midfoot strikers and not good for heel strikers would be an oversimplification, but after a week of Runner’s World staff testing and comparing notes, that’s about where we’re at. I land on my midfoot and I quite like the Carbon X; the rocker feels like a subtle ramp that helps me load up and push off my forefoot, and the shoe feels natural whether I’m jogging or sprinting.
But without extra heel foam to smooth out the roll onto that ramp, I can see why heel strikers find the transition jarring. And it’s worth noting that heel-strikers like Runner-in-Chief Jeff Dengate love Hoka shoes like the Rincon and Clifton, which have the same offset and overall shape but no carbon plate. Our team of wear-testers is currently evaluating the shoe, so we’ll soon have feedback from a more diverse group of runners. Until then, it remains a polarizing shoe that I can only recommend for people who land near the middle of their feet.
A former Division 1 runner, Dan grew up riding fixies and mountain bikes and now reviews everything from performance running shoes to road and cross bikes, to the latest tech for runners and cyclists at Bicycling and Runner’s World.
