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Finlay McAndrew  •  Running Gear •  26.01.2021 •  9 min read

HOKA One One | Carbon X 2 Shoe Review

The new HOKA Carbon X 2 is one of the most exciting models for 2021. The first edition was launched back in May 2019 and was an immediate success. HOKA managed to combine great cushioning with exceptional responsiveness, two features that don’t normally come hand in hand. It sits in HOKA’s Fly range alongside the Rocket X and Elevon 2. Models in this category take inspiration from the weightless sensation of flight while delivering unparalleled levels of propulsion.

Cushioning vs energy return

Soft or highly cushioned shoes are normally more suitable for slower runs as they’re soft and some energy return is compromised as a result. Responsive shoes usually deliver great energy return by being firmer and are therefore less appropriate for longer miles as they don’t reduce the load on muscles and joints as well as softer shoes. HOKA combined their PROFLY cushioning, a highly protective material, with a carbon fibre plate and their signature Meta-Rocker design to achieve amazing cushioning with unrivalled responsiveness.

Runners and triathletes loved the first edition for both training and racing. Multiple Ironman triathlons were won by athletes wearing the HOKA Carbon X. I ran my first sub-3-hour Ironman marathon at Barcelona in 2019 using the Carbon X. There is no doubt that they played a critical role in helping me train for that race and then completing the marathon to the best of my ability. The new Carbon X 2 draws on the success of the first edition. It has been refined to deliver all the key aspects that everyone loves, in an even better package.

Patrik Nilsson, a HOKA One One Elite Athlete and 5-time Ironman Champion said “I really like the Carbon X 2. They are very soft in this strange way, but as soon as you put pressure down, it shoots you forward in an amazing response”.

Carla Molinaro running in Hoka One One Carbon X 2
HOKA athlete Carla Molinaro.

Project Carbon X 2

On January 23rd, 2021, HOKA athletes lined up to attempt to break the 100K world record, wearing the HOKA Carbon X 2. Jim Walmsley set a new 100K American Record of 6:09:26. That translates to 5:57/mile pace! Carla Molinaro, the fastest woman to run the length of Britain, led the women's race for the first 70K. Carla paid the price for pushing the pace early on and dropped to fourth place, finishing in just over 8 hours. The HOKA athletes gave it their all in Project Carbon X 2, inspiring us all to chase our goals and break our own records.

What's new in the HOKA Carbon X 2?


Benefits: softer and lighter foam

It features a new foam which is softer and lighter. The cushioning material used in the Carbon X 2, PROFLY, is an EVA that can be altered in density, from soft to firm, in a horizontal or vertical manner. This enables HOKA to construct a midsole with a soft material that sits on top of a carbon fiber plate, with a firm material that is then positioned underneath.

The result is a cushioned underfoot feel with amazing responsiveness.

While the Carbon X 2 is designed for speed, it’s also designed to deliver great cushioning and protection for daily miles. HOKA have added more of the new soft foam, above the carbon fiber plate, to deliver greater cushioning than the original model. I find this to be very beneficial on longer interval sessions or steadier-paced long runs. I can push the pace in more comfort and my muscles fatigue less as a result of the extra cushioning.

An updated rocker geometry

Benefits: aids propulsion and reduces the amount of effort required to move forward

Fans of the Carbon X will notice the back of the midsole looks quite different. The new shape is designed to complement the softer foam and make landings smoother. HOKA call the curved design of the midsole a Meta-Rocker. This extended Meta-Rocker reduces the amount of ‘work’ that the ankle joint, tendons and lower leg muscles have to do during the gait-cycle. The curved structure creates a rolling motion which aids propulsion and reduces the amount of effort required to move forward. I have traditionally suffered from tight calf muscles and this rocker design has pretty much eliminated any tightness I get in runs.

sole of Hoka Carbon X 2

The new extended Meta-Rocker makes the Carbon X 2 feel even better at a greater range of paces. While runners normally associate carbon fiber plates for fast-paced running, the carbon fiber plate improves the rocker-like action of the midsole and actually makes slower runs feel easier too. I find it almost effortless running at slower paces in the Carbon X 2 because of the forward momentum that the midsole design creates.

A new upper design

Benefits: better fit and lighter but durable materials

HOKA have re-designed the upper based on feedback from wearers of the original Carbon X. The collar shape has been refined to improve the fit and comfort around the ankle area.

An extended heel tab helps reduce friction at the Achilles tendon and makes it easier to put on and take off. This is beneficial for triathletes who don’t want to waste any time in transition putting their shoes on. The first edition was a little tricky to get on at speed.

The Carbon X 2 is incredibly lightweight, 198g and 239g for women and men respectively. A lot of the weight savings come from the upper. An ultra-lightweight engineered mesh upper has TPU infused yarns. TPU is a rubber like material that’s smooth and very durable. This creates a seam free upper that’s very thin but also very durable. I barely notice the upper which is what I prefer in a shoe. I have a thin ankle but relatively broad forefoot. The Carbon X 2 holds my ankle really well while allowing my forefoot to splay out.

Hoka One One Carbon X 2

HOKA's Fly range

Where does the HOKA Carbon X 2 sit in the Fly range?

It hopefully comes across that the Carbon X 2 is a highly versatile shoe when it comes down to what pace it’s suitable for. Most running shoes have a sweet spot, whether that’s fast-paced runs or easier-paced recovery runs and aerobic miles. However, that’s not the case with this performance orientated shoe. The carbon fibre plate, Meta-Rocker shape and PROFLY cushioning make slower-paced runs feel easier and help you elevate the pace during harder sessions or races. I use the Carbon X 2 for everything from easy-paced runs, tempo runs, interval sessions to running marathons.

What session is the HOKA Carbon X 2 best suited to?

Despite it being capable of everything, if you want to save this shoe for certain sessions to get maximum benefit, it would be best saved for tempo-paced sessions, long interval sets and long runs at steadier paces.

The Carbon X 2 offers more cushioning than models that normally deliver high levels of energy return. This extra cushioning helps reduce the stress on joints and muscles so makes it the perfect option for particularly strenuous sessions. I normally feel my sorest, or most fatigued, after long runs at threshold efforts.

A typical summer session for me would be an 18km main set as three blocks of 6km broken down into 2km at 3.30min/km pace, 2km at 3.40min/km and 2km at 3.50km. This turns into a pretty long session with a warm-up and cool-down. I would be pretty sore for a few days after this sort of session in the past. The Carbon X 2 significantly reduces the recovery time needed after this style of session. This makes it easier to be more consistent with my training.

Nikki Bartlett, a HOKA One One Elite Athlete and professional triathlete said “I’ve found, alongside the performance benefits of the Carbon X, my recovery time is instant. I haven’t experienced calf DOMS, something which previously would hold me back for a few days after a session”.

The other options in the HOKA Fly range

The Rocket X

The Rocket X is the lightest and most responsive model in HOKA’s FLY range. Jim Walmsley aptly nicknamed this model the “Speed Dagger”. It features the same carbon fiber plate as the Carbon X 2 but there’s less foam above the plate and it’s firmer. This makes it the perfect option for short and fast interval sessions or races.

Runner in Rocket X

However, some may find this a little too firm underfoot for longer races, like marathons or half Ironman and Ironman distance events. The Carbon X 2 is the perfect race shoe for longer events like these. It delivers the performance that you need to push your pace to the limit, while also optimising protection so your pace doesn’t deteriorate over the course of the run. I would normally start breaking down in the latter stages of the marathon in an Ironman and lose a lot of time in the last 10km. While my form left a lot to be desired at Barcelona, the major limiting factor was my cardiovascular system. The unique structure of the Carbon X helped preserve my muscles so I could push to the end. I’m in no doubt that the Carbon X 2 will feel even better in the next Ironman.

The Elevon 2

This is one of the softer models in the Fly range. PROFLY cushioning is constructed to deliver a soft landing but explosive toe-off. This makes it a great option for runners who still like an energetic feel but want a plusher underfoot feel for easy/recovery runs. An extended heel creates an ultra cushioned feel on landing and an active foot frame creates extra support. This would be a great shoe to use in combination with the Carbon X 2. The additional support and softer cushioning helps take the stress off muscles and joints on easier sessions, when recovery is key. The Elevon 2 is also more durable than the Carbon X 2. Saving the Carbon X 2 for the faster sessions will help you get more miles out of them.

HOKA Carbon X 2 – the shoe for all occasions

To summarise, the Carbon X 2 shoe is capable of anything when it comes to road running. You can run slow, fast and long in them. Most will probably find it’s best suited for steady to tempo-paced runs. Some will find it hard to run in anything else. This lightweight, highly-cushioned and exceptionally responsive performance-orientated shoe is a secret weapon for any ambitious athlete.

Men’s pairs are available now at, with women’s pairs expected to arrive mid-Feb.

Hoka Carbon X 2
The Carbon X 2 shoe is capable of anything when it comes to road running. You can run slow, fast and long in them.

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