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10.4 oz. (295 g) for a US M8.5,
9.4 oz. (266 g) for a US W7
50 mm in heel, 43.5 mm in forefoot (6.5 mm drop)
Easy runs, or fast runs if you can do it
Three layers of bouncy Lightstrike Pro, two carbon-infused plates, Strung upper, Continental rubber outsole
$300, September 15 via the Adidas app and online
THOMAS: There was an experiment where psychologists gave monkeys a singular apple. The monkeys were so happy to have the apple. Like, ecstatic. In the second part of the experiment, the technician gave the monkeys two apples but then took one away, leaving the monkeys with one apple. The monkeys pitched a fit. If you have children, you’ve seen this exact scenario play out somewhere around the age of three. They could only focus on what they lost and couldn’t appreciate the remaining apple.
How does this relate to a shoe review? In regards to the Adidas Adizero Prime X 2 Strung, I’m the monkey.
Short back story: I tried on a prototype of the Prime X 2 Strung at The Running Event in Austin last December. We found out later the shoe probably shouldn’t have been on the floor, but we’re pretty good about keeping secrets, so we promised not to post photos or any defining info about the shoe. However, we did try it on for a quick dash by the booth.
It was only a handful of steps, but I have to say: that shoe blew my mind. It felt like a trampoline. To say that the Prime X 2 Strung was my most anticipated shoe of 2023 would not be hyperbole, and anyone who follows us know that we’ve been teasing it ever since. Adidas would say otherwise, but the production model we received is not the same the shoe we saw at TRE. More on that in a minute.
All that to say, my expectations were loaded coming into the testing phase of the final production model, which we received a few weeks ago. In the beginning, those expectations may have skewed my judgment (and not in a way beneficial to the shoe). I quickly realized I needed to reset and let go of what could have been and test the Adidas Adizero Prime X 2 Strung without comparing it to the prototype. After around 30 miles, I felt I was able to do that.
Before I get into those thoughts, let’s lay out what this shoe is all about. Adidas puts the Prime X 2 Strung into the Adizero racing category, making a point to call it “illegally fast.” The lawbreaking in this context refers to the World Athletics rules reserved for the pros. Namely, that a shoe cannot exceed 40 mm of stack height at particular points in the heel or toe areas, and it “must not contain more than one rigid structure (e.g. plate, blade etc.) whether that structure runs the full length of the shoe or only part of the length of the shoe.”
This shoe blows both those out of the water, as it features three layers of Lightstrike Pro foam stacked up to a height of 50 mm in the heel and 43.5 mm in the forefoot (6 mm drop). That middle layer of foam is a more resilient Lightstrike Pro formulation, and it’s sandwiched between two carbon-infused plates that run the full length of the shoe (the bottom plate is a touch shorter).
The Strung upper is one of the best in the game and has really revolutionized the upper game in the last couple years. This time around it gets a stretch knit tongue that’s seamlessly integrated in the Strung part of the shoe. It’s all finished off with a Continental rubber outsole.
Basically, the Prime X 2 is the pinnacle of all Adidas run technologies. But do the sum of the parts equal a greater whole? Or is it something else altogether? Let’s see if I can get past having to give an apple back.
MEAGHAN: Ohhhh boy, the Prime X 2 Strung. Maybe the most anticipated shoe of 2023 for us? The tagline “illegally fast” couldn’t be more dreamy. A 50 mm stack height? Yes, please. Two carbon-infused plates? Sounds amazing. But, maybe you can have too much of a good thing… let’s find out.
ROBBE: I’m the only person on the team that never tried the previous versions of this shoe, the Prime X and Prime X Strung. I heard quite a bit about them, not just from our team, but from running shoe geeks who absolutely loved the Prime X Strung for its fit and performance.
As Thomas mentioned, we saw a version of the Prime X 2 Strung at The Running Event. It was quite possibly one of the most beautiful shoes ever crafted. Like Thomas, I also tried on the (much too big) shoe, and felt like it was something I never experienced before. It didn’t even feel like running, it felt like parkour trampolining. Again– limited sample size, but enough to get my reviewer heart beating a bit faster.
Now, I’m willing to give up a little bit of my pride to the placebo effect, but I swear that prototype was straight up different than the final product. I’ll get into all that in a second, but point being, I had probably too-high hopes for the shoe. Knowing that shoes always undergo plenty of changes before their final version, I should’ve reserved my excitement for when the final product was in-hand and on foot. C’est la vie, what’s in the past is what’s in the past.
Maybe the Prime X 2 Strung was done in by lofty expectations, or maybe it’s just a case of too much of a good thing. Either way, I learned some lessons, and hopefully you do as well in the following review.
THOMAS: I’m a big fan of the Strung upper. The more you wear it, the more it conforms to your foot. My hot take is that the whole Adizero lineup should have a Strung upper option. Adidas incorporated a stretchy knit tongue that helps to improve the fit. My size 10.5 fits true to size, if not slightly roomy.
Lightstrike Pro has become one of my favorite foams. The foam straddles the sweet spot between soft and mushy. The bounce off the sandwiched puck of Lightstrike Pro is very noticeable. I could feel the pop at slow paces and during all-out strides.
I enjoyed using the Prime X 2 Strung for easy to moderate runs. The shoe can cruise once locked into a rhythm. The best feature of the shoes is how good my legs felt after a long run.
MEAGHAN: The step-in feel of this shoe is something special. It kind of feels like strapping on a pair of Moon Shoes (‘90s kids, you get it). The double carbon-infused plates are very fun and three layers of Lightstrike Pro not only give you tons of bounce, but so much stack. This shoe provides zero ground feel, which is just how I like them.
The strung upper is structured and supportive. Despite not having much cushioning around the collar and heel, it’s surprisingly very comfortable. I did receive a half size larger than my normal W7.5, so there was a lot of room in the toe box (maybe a smidge too much) but otherwise the fit was pretty perfect.
ROBBE: As both Thomas and Meaghan said, the Strung upper is excellent. It’s one of the few uppers that actually looks and feels premium and is doing something you can’t get anywhere else. Meaning, the Spiderman-style webbing is strategically layered in areas of the midfoot and heel that require extra support, while creating targeted flexibility in “expansion zones” on landing. The knit tongue upper is also a nice touch, allowing for great fit with some stretch to keep the top of the foot comfortable.
After the grandmaster chess champion strategizing that goes into other Adizero models like the Takumi Sen 9 and Adios Pro 3, it was a relief to have a shoe that you can actually just tie and be done with. Sometimes, simplicity rules. Which, by the way, is the only simple thing about this shoe.
As soon as you lace up the shoe, you know it’s going to be different. And it is, for sure. You’re standing on the shoulders of two giants, first name Lightstrike, last name Pro. Switch these onto your kids to bump them up to Jolly Rancher level for maximum fun at Hersheypark next summer. The huge stack of Lightstrike Pro and dual carbon-infused plates give a great response if you can get them going. Which is a big “if.” I noticed it most when I really had to gun it, like trying to catch a green light in the city. The bounce really is trampoline-like when it hits the sweet spot.
I enjoyed this shoe most when going downhill. With all the protection underfoot, you can really just let gravity do its thing while the bonkers stack height absorbs all the shock of your definitely fit, definitely superior running body.
With my weak-ass ankles, I was worried about the stability, for sure, but didn’t find it to be any worse than a lot of the thinner-profile racing shoes out there.
I’ll give away the plot, but this shoe wasn’t for me. Why is that good? Because I do think that it’s going to be great for certain runners and I do think those runners will love it. Namely, bigger and/or *much* stronger runners who don’t mind a heavier shoe, and who want a ton of protection while still having fun.
THOMAS: My first run in the Prime X 2 was a workout with fast effort repeats. I found myself fighting the shoe to hold the faster pace. The shoe is bottom heavy. Even with the spring-like bounce off the toes, the shoe’s 11.7 oz./333 grams weight is ever-present. That’s two ounces more than the previous version.
Adidas knows what they need to do to fix the issue. But for you, I’ll spell it out. Start with lighter, thinner, full carbon plates with a puck of spongier foam between the plates, and drop some of the stack if the weight still needs to come down.
MEAGHAN: The biggest issue with this shoe is the weight. Not only because it’s the heaviest shoe I own right now (9.3 oz for a women’s 7.5!) but because nearly all of the weight falls beneath the foot, so it’s wildly bottom-heavy. It felt like I had weights on my feet during my post-run strides.
As much as I love stack, the height on this one does make it quite unstable. I got used to it, but anyone with weak ankles (cough, Robbe, cough) might have some real troubles.
Another obvious issue here is that price tag… dig deep, y’all.
ROBBE: This should go without saying, but it’s good to remind the audience: all shoe reviews are subjective. I like more of a ground feel, I’m 5’6”, I weigh 135 pounds. I don’t know if that’s the determining factor in my following takedown of the Prime X Strung 2, but in fairness to the shoe, you should consider my biases. Maybe it was never meant for me. All that to say, as much as I wanted to have an offline relationship with this shoe, it just felt different than its profile picture and our first speed dating session.
And by different, I mean this was the most disappointing shoe of 2023 for me. I took it out for several runs in the six mile range and decided I couldn’t run it anymore. I gave it to our assistant editor who’s putting miles in it now. Meg put over 50 miles on it and gave up on it too.
It all boils down to one aspect of the shoe: the weight is crazy. It’s not quite the 3D-printed paperweight levels of the 4D-FWD, but it’s definitely a couple late-night pizza slices away from old Ultraboost levels and a half-ounce heavier than the new Ultraboost Light, and everyone knows the UB isn’t a real running shoe.
Adidas said the versions at TRE were the same as the production model. Objectively, that’s just not true as you can see from the two photos below. The middle layer of Lightstrike Pro on the production model is almost completely filled in, whereas the earlier version had a more conservative layer. Did that make a difference? Hard to say, but a weight savings is a weight savings, so it couldn’t have hurt to have less foam in there.
Now, there is some speculation that the changes we saw from then to now may have been due to potential patent infringements. I can’t confirm whether or not that’s true (though I’ll try and find out). However, the reason you see a lot of weird carbon plate configurations and “carbon infused” plates (i.e. Puma Fast-R bridge plate, Hoka parallel plates, Adidas Energy Rods) is partly for performance, and partly because Nike locked down the carbon plate and midsole designs of the Vaporfly and Alphafly, forcing brands to get creative. Then those new designs get patented, and before you know it, there’s slim pickins for the last to market, which is why Altra Vanish Carbon has a Carbitex half-plate (that’s my speculation, anyway).
Like, Nike really covered a lot of bases in their patents. Go to the U.S. patent search site, look up patent 20180213886, and be amazed at the 61 designs within the Alphafly patent, all of which I wish would come to life. I mean, take a look at this 103-page footwear plate patent that has 62 variations on plate designs. That’s the kind of stuff competitors have to work around. So while I’m not sure the Prime X 2 Strung configuration fell into that patent, it may have been included in another one that I’m just not aware of. (Side note: if you’re really bored, going onto the U.S. patent site and looking at all the wild designs and technologies that may or may not be coming to market in a few years is a fun way to pass the time.)
Anyway, let’s move on.
Regarding the weight, nearly every step of every run felt laborious for me (unless going downhill). The shoe is just so bottom heavy that it really does feel like running with weights on. For reference, the half-ounce lighter New Balance SC Trainer v1 is probably the limit for me in terms of weight, but at least that shoe had somewhat of a bounce-then-roll through the stride (it also had a higher drop at 8 mm). The Prime X 2 Strung just felt like a block with bounce. That is, unless you can get it going fast.
When I was able to pick up the speed, it came alive (which makes sense, it’s in the Adizero range). But it’s so hard to get it up to speed and keep it there, that by the time I arrived in that zone, I wasn’t even sure it was worth the effort.
In an upcoming podcast we did with Robbie Paterson, Senior Manager Footwear Development – Adizero Elite Racing, he noted that the Prime X 2 Strung is designed to be a trainer that can double as a fast day shoe. I was actually shocked by that, because I can’t conceive of a scenario where that would be the case, as there are probably six other shoes in the Adidas line that I would pick over this for a faster effort at any distance (Adios, Boston, SL, Adios Pro 3, Takumi Sen, just off the top of my head).
Meg’s humble enough to not pontificate on her incredible training in her lead-up to the Chicago Marathon, but I’ll do it for her– she’s training at OTQ levels right now, with paces that most dudes would envy, and even she couldn’t get it going.
I think every shoe can work for someone, so I try to balance out the bad sections of my reviews, knowing that it’s really hard to make a terrible shoe these days. But I just can’t understand why you’d buy this shoe outside of clout-chasing. If that is the case, good for you, because the shoe is so damn pretty that it certainly looks like a $300 shoe. You’ll definitely get the attention.
The sizing (at least on the lower end of the size range) is way off. Adidas recommends going down a half size, but I would go down a full size. I passed off a men’s size 7 (yes, we’re almost in kids territory) to our assistant editor who’s a men’s 8, and it fit him perfectly.
Last thing on this: Regarding my previous expectations of the shoe, I can fully admit it’s possible I was simply biased by what I saw and/or wanted to see in the early version of this shoe. If that’s the case, I’m willing to admit I was wrong. Clearly, I’ll be tempering my expectations in the future, even though this is probably the last time we’ll ever see a prototype at The Running Event. Either way, the final result is a shoe I just can’t get into.
THOMAS: My first thought was disappointment. I was sad. Someone had taken my apple. Once I overcame the initial letdown, I could enjoy the shoe for what it is. For starters, it is not a racing shoe, illegal or otherwise. The Prime X 2 is a cruiser. During a 10-mile run, I enjoyed the well-cushioned bouncy ride. I just locked in the pace and floated along with a couple of running buddies. My feet felt great after, and I looked forward to running in the shoe again.
If it weren’t for the $300 price tag, the Prime X 2 would be a great companion for the Adios Pro 3. Runners could do long slow distance in the Prime X 2, then switch out to the light Adios Pro 3 for fast workouts and races. However, with that combo you’d be down $550.
The runner that might benefit from the Prime X 2 the most could be the Clydesdale or plus-size runner. There’s a lot of cushion, the weight may be less noticeable, and the extra force and compression on the double plates could make the shoe sing.
Before putting together this conclusion, I went back to the original Prime X Strung for another run to see how it compares to the Prime X 2. The original is two ounces lighter, and while the carbon Energy Rods in that shoe don’t have the extreme bounce off the toe that’s found in the three-foams-two-plates of the X 2, it remains bouncy and fun.
If Adidas could add in the plate/pillow combo and keep the weight closer to the original, they would have some real magic on their hands. I’d recommend the original Prime X over the X 2, especially if you can find it on sale.
MEAGHAN: The Adidas Prime X 2 Strung isn’t a bad shoe, but it might be the most disappointing. The original Prime X Strung was so much fun and I had such high hopes for the second iteration. Unfortunately, I felt like this was a step backwards. The weight of v2 takes away from the fun bounciness of the original, and I just couldn’t ever get into a smooth rhythm. While I wanted to love this shoe, at $300, this one is going to be a pass.
ROBBE: The original Prime X Strung had a price justification– it was all the magic of the excellent Adios Pro 3, with a higher stack midsole wrapped in a reasonably lightweight package. The Prime X Strung 2 shoe is an island on its own, an untethered anchor.
While Meg doesn’t think this is a bad shoe, I have to disagree. I think a $300 running shoe that doesn’t deliver on its promises is a bad shoe. Obviously you can run it, obviously it’s going to work for some people, obviously a big layer cake of Lightstrike Pro isn’t going to feel like trash underfoot. But if the performance returns can be found in scores of other shoes at almost half the price, I’m just not buying it.
I know this shoe can be great– not just for a select few, but for everyone, out of the box. After all, the last version of this shoe was exactly that. And I really, really love the “f*ck it, let’s break all the rules” attitude that Adidas is going with. I wish more brands would go there instead of staying stuck in their conservative, money-printing model lines. But a miss is a miss.
Honestly, the “one step forward, two steps back” reality of this shoe makes me even more excited for the next version, because I know they know what they’re doing. The vision of Adizero is on the right track. While this is a step (or two) backwards, I’m confident the next version can be a moon leap forward.
You can pick up the Adidas Prime X 2 Strung for $300 on September 15 at adidas.com.
As the founder of Believe in the Run, Thomas’s goal is to help runners pick the shoes and gear that will make their running experience the best that it can be.More from Thomas
Meaghan signed up for her first marathon three weeks before the race, because it was $10 more than the half she planned to run. She learned everything in running the hard way. Now a USATF & UESCA certified run coach, she loves encouraging friends to go for big goals as she continues to chase faster times. She enjoys a hot cup of coffee, a cold martini, and making bagels for friends and family.More from Meaghan
Robbe is the senior editor of Believe in the Run. He loves going on weird routes through Baltimore, finding trash on the ground, and running with the Faster Bastards. At home in the city, but country at heart. Loves his two boys more than anything. Has the weakest ankles in the game.More from Robbe