Editor rating:
9/10 on
BRANDON LAW
User's rating:

PROS

  • Breathable upper
  • Aggressive rocker
  • Natural-feeling ride
  • Maximum cushioning
  • Excellent forward propulsion

CONS

  • Very unstable when cornering
  • Uncomfortable lacing pressure
  • Illegal for World Athletics events

OUR VERDICT

The Adidas Adizero Prime X is a max-cushioned super shoe with a high toe-spring and an aggressive rocker.

It functions best as a racer for half marathons and shorter (non World Athletics events), or as a training shoe for short tempo or speed workouts.

It proves that a midsole stack height of 50 mm with more than 1 carbon plate does provide a speed advantage.
WHERE TO BUY
LOWEST PRICE
$250
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SHOE INFO
Brand
Prime X
Model
Type
9.25 oz. (262 gr.)
Weight
250 US$
MSRP
50 mm
Heel
10 mm
Heel Drop
WHO IS IT FOR
If you're a runner who doesn't need much stability and you're curious to try an experimental super shoe with a 50 mm stack height, the Prime X is for you.

Adidas Prime X Intro

Competition is a beautiful thing. It spurs us on to innovate, push the boundaries. Without competition, brands and consumers would settle for ordinary, mundane products.

Last year Nike launched the Alphafly Next%, a super shoe behemoth which Nike threw everything but the kitchen sink into in terms of cutting-edge running shoe technology.

This year, it’s Adidas’ turn. The Prime X dwarfs even the Alphafly and it looks somewhat like an experimental project: an unrestrained, wild example of what Adidas can invent if there are no restrictions.

The Prime X clearly takes inspiration from the legal Adidas racer, the Adios Pro 2 : both have carbon-infused Energyrods, plates in their heels and use only Lightstrike Pro foam.

However, the biggest differences between the two are that the Prime X has even more midsole foam and additional carbon-infused blades in its forefoot.

On the 31st of January 2020, World Athletics announced that shoes with soles thicker than 40 mm would be banned from official World Athletics events.

They also stated that shoes with more than one embedded rigid plate or similar device would also be banned.

So here we have the rebellious Adizero Prime X that breaks not one but two of the rules. So does a midsole stack height of over 40 mm and more than one carbon plate really provide an unfair speed advantage?

It’s rumoured that the Alphafly prototype Kipchoge used to break 2 hours for the marathon distance was over 40 mm in stack height and had more than one plate embedded in its midsole.

That version of the shoe was never made available to the public so none of us could test it but fortunately, the Prime X is now available to the public in all its 50 mm glory.

Adidas Prime X First Impressions

Adidas Prime X - Front Lateral

Adidas Prime X – Front Lateral

I had heard rumours that there would be a new Adidas super shoe with a stack height of over 50 mm earlier in the year.

The concept of an illegal racing shoe that breaks the rules set out by World Athletics is a great idea and I wondered why other brands hadn’t done it sooner.

Months passed and there was no news of this rumoured super shoe however when I was alerted by the local Adidas store that they were in stock, it felt like Christmas morning.

The first time I saw the Prime X in real life, I was thunderstruck by its immense size.

This is a shoe that definitely has a “wow” factor and I’m sure many celebrities will be wearing it for the fun of it, just like with the Alphafly. Cue Conor McGregor walking to the Octagon in the Prime X.

When I tried the shoe on in the store, it was unlike anything I had ever worn before. The midsole was so thick that I felt like I was balancing on stilts.

There was too much space in the forefoot so I decided to go down a half size. This ended up being the perfect size for me.

My first run was an interval session and it was the most fun I’ve ever had during a speed workout. It made the interval session feel “easy” which is something I never thought I’d say.

During the warm up, when I was running slowly, the Prime X felt unstable and very average, however during the workout when I needed it to perform, it turned into a completely different beast.

At speeds of 4.15 minutes per kilometre, which is fast for me, I felt like I wasn’t putting in as much effort to reach those speeds.

I felt like I was putting the same amount of effort as when I go slower, around 5 minutes per kilometre.

The sensation that stood out the most was how the shoe was rolling me and then throwing me forward with every toe-off. It was the most aggressive rocker I’ve ever felt.

The Adios Pro has a very gentle, mild rocker compared to the Prime X which is like a catapult that shoots you forward. Those 3 extra carbon-infused blades in the forefoot really make a difference.

The ride also felt very protective: by far the most cushioned of all the super shoes I’ve tested and the lowest level of ground feel.

After that first run, which was the best first impression I’ve ever had, I never wanted to do workouts in another shoe and I couldn’t wait to test it on longer efforts.

Adidas Prime X Sole Unit

Adidas Prime X - Heel Closeup

Adidas Prime X – Heel Closeup

The ride of the Prime X is most similar to the Adios Pro but everything is intensified. It’s like a souped-up Adios Pro. The cushioning is softer, the rocker is more aggressive and the propulsion at toe-off is greater.

The Energyrods do a good job in keeping the midsole stiff so that the rocker can do its job effectively without the midsole flexing.

In the Adios Pro, you can vaguely feel the Energyrods but in the Prime X you can’t feel them at all beneath the mammoth chunk of midsole foam.

The monstrosity that is the Prime X’s Lightstrike Pro midsole is relatively light for its massive size.

The Prime X weighs less than daily trainers like the Boston 10, Ghost 14 and Pegasus 38 but it offers far more cushioning which is impressive.

With such a thick midsole, you’d think that the ride would be really unstable- and it is. Especially on long distances when you’re going at a more controlled pace, you really have to concentrate on how and where you strike.

It favours forefoot strikers over heel strikers because of its narrow waist and rearfoot.

When going around a corner, you have to make sure you slow down to snail pace because there is so much pressure on your ankles.

Adidas Prime X - Sole Closeup

Adidas Prime X – Sole Closeup

For me, Prime X is best suited to shorter runs like interval speed workouts or short races on a straight route.

Long marathon distances are doable but the instability really takes its toll on your ankles and you exert a lot of energy trying to stabilise so that you don’t roll an ankle.

It turns into an ankle strengthening workout that you never signed up for.

You also need to be going at fast paces below 5 minutes per kilometre to benefit from the rocker. You have to lean forward and push off hard with your toes.

So the big question is does the 50 mm stack height make a difference in terms of speed? In my experience, yes.

The higher off the ground your foot sits, the higher the toe-spring can be and the more aggressive the rocker can be.

While the Adios Pro rolls you forward gently, the Prime X throws you forward because of its more aggressive rocker but the ride still feels surprisingly natural.

The 3 blades in the forefoot also make a difference: they aid the rocker by making the forefoot more rigid which makes transitions smoother and more snappy.

The outsole is a big strength of the Prime X. Unlike the Adios Pro, which has a thinner, modified version of Continental rubber, the Prime X has the normal, thick, durable Continental rubber.

This means that the Prime X is durable enough to be used for training because you can get so many more kilometres out of it than the Adios Pro.

I’ve run 81 kilometres in my pair and the only visible wear is on the exposed midsole areas.

I like the fact that the outer lateral heel rubber patch is already smoothed on the high wear area so your wear doesn’t show as much in the initial stages.

Traction is what you’d expect from Continental: super grippy on all types of terrain, even in heavy downpours.

Adidas Prime X Upper Unit

Adidas Prime X - Top

Adidas Prime X – Top

The Prime X’s upper is light, breathable and minimal. It’s made from transparent Celermesh 2.0 which is porous and plastic-like in feel.

One of my runs was in heavy rain and the upper was fantastic. The Celermesh absorbed no water- only the laces and my socks picked up weight.

The flat tongue is sewn onto the eyestay on both sides so that no tongue slide occurs which I found refreshing for a super shoe.

There are some flat underlays on the midfoot and the sides of the toe box for reinforcement and to give the shoe extra structure and support.

A thin internal heel counter suede internal heel counter provides some heel support while there is also suede material attached to the collar lining for extra comfort.

I experienced no heel slippage when using a runner’s knot and overall foot lockdown is good.

Being a first-generation shoe, there is bound to be a weakness and the Prime X’s biggest weakness is related to its eyelets and eye stay.

There just isn’t enough padding between the foot and the eyelets so when you tighten the laces, you feel uncomfortable lacing pressure on the top of your feet.

You could loosen the laces to relieve the pressure but then your feet move around inside the shoe so much that it becomes even more unstable.

The fit is definitely a half size large with an accommodating, roomy, training shoe type of fit. This is a super shoe that is suitable for wide footed runners.

Adidas Prime X Conclusion

Adidas Prime X - Inner

Adidas Prime X – Inner

The Prime X is an absolute joy to run in and is unlike any super shoe I’ve ever tested. It’s experimental projects like this that shoe reviewers such as myself live for.

It’s not the most versatile shoe but it’s still my favourite to do speed workouts and short tempo runs in because of its giant rocker that throws you forward.

I don’t feel as much raw propulsion in the Prime X as in the Metaspeed Sky or the Vaporfly Next% 2 but the difference is that the ride of the Prime X feels more natural and it takes less effort to maintain fast speeds.

If you have a very neutral foot strike and strong ankles, the Prime X would make an excellent long run shoe because it has plenty of soft cushioning that pillows your legs while its rocker saves you energy.

The Prime X is definitely the most unstable shoe I’ve ever worn and it’s this instability that severely limits its versatility for me. It also doesn’t have enough upper padding so you can feel the eyelets on top of your feet.

So is the Adizero Prime X a training shoe or a racing shoe? On the one hand, it has plenty of thick outsole rubber for training sessions but on the other hand, it has a minimal racing upper with only the bare essentials.

I’ll be using the Prime X for training and shorter races: interval workouts, short tempo runs and half marathons.

I don’t feel comfortable using it for runs longer than 21 kilometres because my form just isn’t good enough for extended periods and it takes a lot of concentration to run in the shoe to make sure you are always forefoot striking and slowing down at turns.

Compared to the Alphafly Next%, the Prime X is a lot more fun and it’s also $25 cheaper but it’s not as practical.

It’s not nearly as stable and its upper is not as good as the Alphafly’s. You also can’t race in an official World Athletics event in the Prime X but you can in the Alphafly Next%.

Adidas Prime X - Lateral Closeup

Adidas Prime X – Lateral Closeup

This begs the question, why did Adidas create the Adizero Prime X?

It’s possible that Adidas was already working on the Prime X before World Athletics announced the new rules but Adidas still decided to go through with it.

Another reason could also be that Adidas wanted to outdo the Alphafly Next% by making the Prime X bigger and more aggressive, no matter what the cost.

Whatever the reason, I’m glad they went through with it because it confirms that a midsole stack height of over 40 mm and more than 1 carbon plate really does provide a speed advantage.

If elite marathon runners were allowed to race in the Prime X, I’m sure there would be plenty more records broken.

We purchased a pair of Adidas Prime X from runningwarehouse using our own money. This did not influence the outcome of this review, written after running more than 50 miles in them.

Adidas Prime X Price Comparison

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