The Carbon X is not HOKA’s answer to the Nike Zoom Vaporfly 4%. I suspect that would be HOKA’s Evo Carbon Rocket, in which I haven’t run and don’t really expect to. Both those racing flats are in the 7oz range, plus or minus, and the Carbon X, at 8.7oz, isn’t even among the top half-dozen when ranking HOKA’s shoes by weight.

Carbon X is more a lightweight trainer, by category, but it’s going to be my racing flat and maybe it should be yours too. I suspect the closest Nike analog to this shoe is Nike’s $250 Vaporfly 4% Flyknit, which is more than an ounce heavier than the original $250 near-unobtainable racing flat, and is about ¾ of an ounce lighter than the Carbon X. I’ll take the extra ¾ of an ounce any day, for reasons I’ll describe below.

First I’d like to spend a moment on the provenance of today’s carbon-plated roadracing shoes. There’s a lot of intrigue here. When I write that HOKA’s shoes were the “answer” to Nike, it may be that the Vaporfly was the answer to the statement HOKA never got a chance to make. Confused? The Zoom Vaporfly 4% is not the first shoe with a carbon sole (it’s about 30 years too late for that), nor is it the first modern shoe that experimented with the carbon sole. And this is where John Le Carre could’ve written Tinker, Tailor, Shoemaker, Spy.

HOKA had itself been seriously investigating carbon plates for some time, according to a number of those close to the company. By one account, Jean-Luc Diard (I’ll write about him more below) had been experimenting with this back in 2014 (mind, I haven’t asked him about this). Just, coincidence or not, while Diard is still at HOKA and has been there since he co-invented the shoe, HOKA’s talented lead product manager fled for Beaverton and – behold! – Nike not long thereafter produced a carbon run shoe. As to personnel changes, there’s more to the story, it’s a pretty interesting story, a cautionary tale really, but not germane to the shoe I’m reviewing. What I don’t know is whether the product manager arrived at Nike with a headful of carbon shoe plate insight, or whether Nike independently created the Vaporfly.

Nike already had a big head start in carbon “footwear” through making carbon prosthetics for runners. Perhaps one day I’ll have a chance to talk to Nike’s Athlete Innovation Director at Nike, Tobie Hatfield, and get more of the backstory on the Vaporfly. Hatfield’s analog at HOKA it’s the aforementioned Mr. Diard, Global VP Innovation At HOKA, a brilliant innovator and businessman. While CEO at Salomon Diard spent decades of his business life on the mechanics of how longitudinal carbon springs perform underfoot; there is no one with a pedigree more apropos to a carbon plated run shoe than this man.

I would also not discount the possibility that a little bit of Stuart Jenkins found its way into the Carbon X. Read Diard’s recommendation of Jenkins on Diard’s LinkedIn page, and then contemplate that Jenkins was a prime mover in the carbon plates in Etonic, Mizuno and Reebok shoes well back before the turn of the century.

Anyway… after Nike’s success with the Vaporfly it doesn’t surprise me that HOKA responded with a shoe, and maybe there was no “re” about it. Maybe HOKA just “ponded” (is that a word?). Maybe the Carbon X, and the Evo Carbon Rocket, are the shoes HOKA always planned to produce; and maybe HOKA was first to concept, just, second to market, behind Nike. I don’t know.

In any case, I got hold of 2 pair of the Carbon X, 1 to construct as a triathlon shoe (with lacing for quick transitions), and 1 pair for conventional footrunning (regular laces, for use with socks). I’ve done some multisport racing in this shoe, quick-transition, sockless style, and I’ll tell you what I think.

Just, as to construction, the crux of it all is the carbon plate. The Vaporfly had one, packaged with the gold plated marketing effort behind that shoe. I’ve never seen a Slowtwitch audience whipsawed by a product intro as fast. Slowtwitchers wouldn’t give Nike the time of day. That brand inched up, from 5 percent use to about double that, between 2014 and 2018. Then, when the Vaporfly came out, Nike as your brand preference for your racing flat instantly doubled, from 10 to 20 percent (equaling your preference for HOKA).

Let me say that I have not run in the Vaporfly, so I can’t give you the comparative analysis. I haven’t run in the Vaporfly because I can’t run in the Vaporfly. I’d sooner jump out of an airplane in a squirrel suit. Nothing against that shoe. Just, I’m a 170lb overpronator who’s already spent 3 blocs of time during my life unable to run for one injury or another. I will not run without an orthotic. I will not run in a shoe that can’t support an orthotic. Nike’s shoes famously, notoriously, reliably, fail to support my foot. If and when Nike chooses to make a shoe for a man who is not a 125 pound, low-2hr marathon runner, they know where to find me.

Mind, I love the fact that Nike – to the exclusion of all other footwear companies – understood the value of forefoot cushion (going back to the Air Mariah, Sock Trainer, Sock Racer) for the past 30 years. Nobody got it, until HOKA came along and out-cushioned Nike (especially in the forefoot!) and out-engineered Brooks.

Before I continue, for those of you who’d like to lecture me gently on how I can run injury free forever if I just strengthen my foot muscles, etc., I don’t mean to be shrill. Just, have you been running competitively for 50 years almost continuously? And you’re healthy today? Do you reliably prevail over those in your competitive set, whether in a triathlon or in a standalone footrace? Great! Because I haven’t. I’m only in year-49. If you check all those boxes, I’m eager to hear your wisdom (which is why I absolutely do listen to Gene Dykes). If not, bless your heart, but in this article you get to hear my wisdom (there’s a Facebook utility just below where I’ll learn the error of my ways).

I was a Clayton user at 5k and below because the Clayton was just, barely, enough shoe to support an orthotic. (There are comparative looks at the Clayton and the Carbon X sprinkled through this review, the red/white/blue Carbon X is one colorway; my blue/white shoes are the other.) These 8oz Claytons perform for me because there’s enough beef in the shoe’s waist to keep that orthotic from caving in on the medial side. If the arch is sculpted out (as with the case with many racing flats, most of Nike’s included) the orthotic will destroy the shoe pronto. The Clayton, because it retains the HOKA features, earns the right to bear the HOKA name (whereas the Tracer never did). Mind, the Clayton’s support structure was barely sufficient. The Clayton’s heel feels as if it’s made of papier mache. It’s a little hard to get on in transition because it felt like wrapping whipped cream up over my heel. But it worked. It was cushier than sin and, as regards my footfall. It let me be me.

While the Clayton and the Carbon X function similarly, they are pretty different shoes mechanically. If you look at the bottoms, they’re each substantial enough to support triathletes and let me explain this. Once upon a time I outfitted just about every good triathlete in the world with wetsuits. Because of that, I acquired an education on what a triathlete was, and is. He’s 160 pounds, if we’re talking men, and this is the weight of the athlete if he’s among the world’s elite. Our best-ever male triathletes, at least at the Ironman distance, have been within a few pounds of 160 pounds (excluding the occasional outlier).

Our shoes cannot be the same shoes made for elite runners 40 pounds lighter. This is why I say to you that the Carbon X, and not the Evo Carbon Rocket, may be your best racing flat. Too often shoe companies ascribe use case to their products, when they should simply ascribe features and let the user determine the use case. Happily, HOKA does not do that with this shoe. It may be Donn Cabral’s trainer, but it’s my racer.

The HOKA Carbon X is similar to the Clayton in cushion – and probably exceeds the Clayton in that feature. It may be slightly more robust than the Clayton, though like the Clayton has that very fungible heel. I don’t find that I need the heel to be more rigid for this shoe’s use which is, for me, racing (I currently train in the Bondi B reissue) and the very occasional fast training session on a predictable road surface (a trail shoe it ain’t).

If it’s like a Clayton; if it’s no lighter than a Clayton; why not just run in a Clayton?

Note that there’s an obvious leading and trailing edge to this shoe, quite rounded, to keep the shoe from scraping on impact, and levering the foot upon impact. There’s a significant Rocker in this shoe, maybe it’s my imagination, but it seems to me to promote the transition from impact to push-off and if it does I suspect it’s due to the shape of the carbon plate. I won’t really know until I wreck this shoe enough to – argh! – finally take my Sawzall to it and see what’s inside it.

He who spends the least time on the ground runs the fastest. What you don’t want is to hit the pavement, have your foot enjoy a little party there, communing with the asphalt. Your foot wants to be like Southwest Airlines 737: Hit the tarmac, empty the airsickness bags, herd the cattle in, wheels up. My sense is that this is what a carbon plate in a shoe tries to promote. Maybe I’m just feelin’ groovy lately but I when I run in these shoes I get the sense that the shoe is trying to hurry up my time-on-ground, and that’s a good thing.

I’ve raced twice, sockless, in multisport events, in the Carbon X and here’s what I have to say good and bad about this shoe. I got no blisters at all the first race; I got a slight bit in the second race; nothing major; but I find that I need to wash this shoe after races or else the upper gets hard, crackly, and that impacts the comfort when I’m running sockless in the next race. Comfort-wise the shoe is very well suited to what we do in triathlon. There’s a heel loop, but look at the difference (above) between the heel loops in the Carbon X (background) and in the Rincon (foreground). A loop like this would benefit the Carbon X. If you’re going to make the heels of these shoes formless – which is fine – please give us something to grab onto when we need to get the heel of the shoe over our feet.

I didn’t find the shoe the easiest to get on in transition, but I think you probably will. I’m still fiddling with the lacing pattern. I’m enough committed to the shoe to experiment until I get it right. I’d like this to be an on-while-standing process and, for me, it isn’t yet. I’ll probably move to a system with lace locks.

The Carbon X costs a lot of money, at $180. Before you complain, be aware that the aforementioned Rincon, in which I haven’t yet run, will debut at $115, so HOKA seems committed to runners at various spend levels. Also, bear in mind what Nike charges for its carbon-plated shoes.

Here is the HOKA One One Carbon X; here is the Nike Vaporfly 4% Flyknit. I’ve given you the links to the shoes on each company’s web page. Read the user reviews on each page. Look at the number of reviews of the Nike. There’s a very high number of over-the-moon reviews. But there’s also a troubling number of reviews about how quickly this shoe breaks down. Of course this Nike is a 7.6oz shoe, and if you take an ounce off the Carbon X maybe it’s not going to hold up as well. (But, then, maybe that’s why HOKA didn’t take that ounce off!)

This shoe comes in mens half sizes from 7 thru 13, and then jumps to a 14. In womens, it’s available in half-sizes from 5 thru 11. The 2 colorways are the same for both mens and womens versions.