If you already own the Adidas Adios Pro 3 and you’re looking for something with more cushioning and more speed assistance, the Prime X 2 Strung is the shoe for you.
If you’re looking for a light racer with a natural ride, the Prime X 2 Strung is a shoe that you should pass on.
The Prime X was supposed to be Adidas’ marathon racing shoe but after World Athletics announced that shoes 50 mm and over in stack height would be illegal to race in, they had to create the lower-stacked Adios Pro. Luckily for us, Adidas still chose to release the Prime X to the public.
The Prime X in my opinion is one of the most unique, engaging running shoes that you can buy and I loved the previous 2 versions. The only thing I didn’t like about them was how unstable they were due to the tall stack height and the narrow midfoot/rearfoot. They were also much heavier than other racing shoes but I didn’t mind the weight.
In the past year, I used the original Prime X Strung for intervals, long runs and tempo runs. I loved the extreme forefoot rocker and how much cushioning you get underfoot. It’s also a really durable shoe because the outsole is thick and hard-wearing.
The Prime X 2 is actually the third version of the Prime X. The Prime X Strung, last year’s version had the same midsole and outsole as the original version but with an updated upper. The Strung upper was a lot more comfortable than the upper of the original version but it also made the price skyrocket.
The Prime X 2 weighs 10.4 oz (295 g), which is a substantial 1.4 oz (40 g) heavier than the previous version. The stack height is still 50 mm in the heel, but the forefoot is 3 mm higher. It’s now 43 mm in the forefoot and it still costs $300.
My first run was a speed workout of 3 x 2 kilometres. I could tell immediately that I liked it more than previous versions of the Prime X. The most noticeable difference was the increased stability. My landings felt a lot more planted and going around corners was much easier.
Each interval was about 15 seconds per km faster than I predicted it would be before the run and the high level of speed assistance that was present in predecessors was still there. The forefoot also felt slightly softer due to the increased stack height.
I was a little bit disappointed that I couldn’t feel the boost from the “spring” in the forefoot which consists of the soft Energy Core in between the 2 plates. This was the feature that I was most excited for but I was still excited with the Prime X 2’s overall performance during the first run.
The Strung upper of the Prime X 2 is now a semi bootie construction, with a knitted tongue which is attached to the rest of the upper. The Strung part of the upper consists of thousands of soft strands which have been fused together. I find it really comfortable but breathability isn’t as good as on other racing shoes.
I prefer last year’s upper because foot lockdown was better. With this new version, the fit is more relaxed due to the stretchy tongue and I find the heel a bit loose. There’s no heel slippage but I notice the loose heel on every run.
Normally with bootie uppers, you can’t tie a runner’s knot but Adidas cleverly engineered the Prime X 2 to have 2 plastic pieces attached on the outside of the upper which have 2 holes each, enabling you to tie a runner’s knot. I need to tie a runner’s knot or the fit will be too loose.
The fit is more true to size than last year’s version- there’s less space inside the upper but I still recommend getting your regular size. This is one of the more accommodating racing shoe uppers so it’s great for long runs and suitable for wide feet. Just like previous versions, there are no reflective elements on the Prime X 2’s upper.
The Prime X 2 takes full advantage of its 50 mm stack height by creating a super aggressive toe spring and rocker geometry which throws you forward when you’re going fast. The thicker the midsole, the higher the toe-spring can be.
During toe offs, you can lean into the forefoot and engage the extreme rocker. This is the main reason the Prime X 2 feels so fast.
My favourite new feature of the Prime X 2 is the increased stability. This is due to the extra piece of foam under the arch where there was previously a cutout. The midfoot and rearfoot are also wider than previous versions so it’s a friendlier shoe for heel strikers and over pronators.
I find that the Prime X 2 performs better than the original during long runs as a result of the more planted landings. I also feel that the change from EnergyRods to a regular carbon plate makes the shoe more stable.
There are 2 plates in the Prime X 2: the top plate is full-length & carbon fibre while the bottom plate is a 3/4-length, carbon-infused plate. In between the 2 plates is an Energy Core, a softer foam which Adidas states has more energy return than regular Lightstrike Pro but I don’t notice a difference.
I wish the Energy Core was softer because I’m only 60 kilograms so I don’t feel it compress and spring back during toe offs but I understand that there are runners who are much heavier than me and if the Energy Core is too soft, the plates will touch each other when loaded.
With such a thick midsole and 2 carbon plates packed into it, the Prime X 2 is the stiffest shoe on the market and the midsole doesn’t flex at all. This allows the rocker to function much more effectively than a racer with a flexible plate in it.
At 10.4 oz (295 g), the Prime X 2 is a lot heavier than any other super racer on the market but I don’t mind the weight over short/middle distances. The benefit that I get from the speed assistance is worth the weight sacrifice.
The longest run I did in the Prime X 2 was 30 kilometres at target marathon pace. For the first ⅔ of the run, I didn’t notice the weight but for the last 10 kilometres, my legs started to tire and I had to dig really deep to complete the workout. The Prime X 2 excelled at every other run I did in it: hill sprints, easy runs, steady runs and intervals.
The outsole rubber on the Prime X 2 has been modified. It’s now the same “sandpaper” type of Continental rubber that you find on the Adios Pro. With this type of rubber, the grip is superb for the first 150 km but after that, the grip starts to decline. It’s also much thinner than regular Continental rubber so it wears down to the midsole foam at a faster rate.
I ran after it had just rained so the roads were still wet but the outsole grip of the Prime X 2 was fantastic.
I’ve already put over 92 kilometres on the Prime X 2 when I’m only required to do 80 before I write my review. This is testament to how much I enjoy running in it.
There are things that I like about the new Prime X 2 like the wider base and the softer forefoot but there are also some things that I dislike: the looser upper, the increase in weight and the thinner outsole rubber.
I still think it’s an overall improvement over the last version because it’s an easier shoe to use. You don’t need to concentrate on landings as it’s a lot more stable. This will suit a wider range of runners.
The Prime X 2 is a really fun shoe but it’s definitely not worth $300 and if money matters (it does for most runners), the $250 super shoes like the Rocket X 2, Vaporfly 3 and Adios Pro 3 represent much better value. This is a supplementary shoe for runners who already have a marathon racer and are looking for something different.
As far as performance goes, I feel more speed assistance from the Prime X 2 than any other running shoe on the market so I’m seriously considering using it for my next marathon in 2 weeks. My biggest worry about using the Prime X 2 for racing is its hefty weight, which is 3 oz (85 g) heavier than the average marathon racer.
The average runner completes a full marathon in 40 000 steps. If I’m carrying an extra 3 oz on each foot, over the course of the marathon, I will be carrying an extra 3402 kilograms on my feet and I’m not sure the extra speed assistance will offset the extra weight.