adidas Ultra Boost ST review
The buttery rubber shredded faster than one could say Ultra Boost, and it was slippery as an Japanese eel slithering on the docks. So when adidas announced that its newest Ultra Boost ST came shod with a Continental rubber outsole, there was ample reason for cheer.
As far as traction goes, it does not disappoint. The Ultra Boost ST’s outsole provides optimal grip on a range of surfaces from paved roads, concrete, and even manhole covers made of metal. Traction is one area where the ST excels at, and you can rest easy even when running in the rain.
And what of the durability, which was a **huge** issue on the original Ultra Boost? The answer can be split into two parts, first being the outsole design, and second pertaining to the rubber compound used.
1)
Much wider midsole waist. 2) Increased under-heel coverage. (note: this
year’s updated Ultra Boost comes with a flat-nubbed Continental
outsole. What’s pictured here is last year’s UB with its pointed outsole
lugs)
The fundamental difference here happens to be the ‘flattened’ profile of the individual rubber nubs, as opposed to the pointy nubs of the UB. By the way, this year’s Ultra Boost update also features this flattened outsole construction.
Which is a smart move. Since the pointed outsole design ended up being flattened anyway after 30 miles, so why not have a flattened design to begin with? Incidentally, the flat profile also improves traction with increased outsole contact area.
Think of the ST’s Continental rubber as soft car tires. Great on grip, but not quite the interstate cruiser.
The obvious trade-off happens to be durability. While the ST fares better than the 2015 UB’s outsole, the upside isn’t substantial. Everyone likes data, so if we were to throw a subjective number, the ST is around 20% more durable than the quick wearing rubber of last year’s Ultra Boost. So to recap, don’t expect Supernova Glide Boost levels of outsole life – you will not get it.
Let’s pause here for a moment. We’ve gone on and on about the new outsole and how nice Vancouver is, but have said nothing about the actual shoe so far. What exactly is the Ultra Boost ST, and how is it different from the original Ultra Boost? Fair question.
How exactly does the Ultra Boost ST work?
This isn’t a stability shoe in the conventional sense. The ST isn’t firm, does not come with a harder medial post, and hence does not display any mannerisms expected of a traditional ‘stability’ or ‘support’ shoe.
When speaking of the ST, the Brooks Transcend comes to mind. Unlike the Brooks Adrenaline GTS 16 or the Ravenna 7, the Transcend does not rely on a firm foam/soft foam midsole set-up. Instead, it uses lots of foam on a very wide midsole base which increases in volume going from lateral to medial. And the result?
A very cushioned and planted ride, helped by the wide footprint and tall midsole sidewalls. Another aspect unique to the Brooks Transcend is its prominent feel of under-arch support; this was due to the midsole’s generously foam fill and flare under the arch area.
When seen from that point of view, the adidas Ultra Boost ST is exactly the same. It has neutral ride manners packaged within a highly cushioned experience. And much like the Brooks Transcend, the ST midsole is designed to deliver a noticeable level of under-arch support – with none of the usually associated firmness.
But hey, the ST comes with a medial support structure, does it not? Yes, there is a support element on the inner side of the Boost midsole, but it does not work in the way one would expect.
That said, the green midsole band is far from being purely cosmetic, and comes with a function to perform – but in a very ‘non-motion control’ sort of a way. We’ll delve into that in more detail after we run through the basics.
There are a lot of similarities with the standard Ultra Boost, beginning with the name.
adidas’ magic potion – a cluster of springy Polyurethane globes fused together in the shape of a midsole.
By the way, for those who aren’t up to speed on adidas tech, the Boost midsole happens to be a cluster of blown Polyurethane globules molded together. This was developed by BASF, the chemical company, and you can read all about it in our review of the Energy Boost.
Regardless of the visual common ground, the Ultra Boost ST couldn’t be more apart than the non-ST version. The Primeknit upper used on the ST is completely different. While the Ultra Boost featured a stretch compression mesh, the ST mostly sticks to the use of non-stretch Primeknit.
The
ST uses a Primeknit upper, but stretchy it is not. Except for the green
band around the forefoot, which happens to be slightly elastic.
This makes only the green forefoot band slightly expandable, while the remaining upper area lacks any stretch worth mentioning.
The Lycra fibers are used in areas other than the green forefoot band, but then, a grey knit structure covers those areas and limits the amount of stretch.
It is interesting how adidas has quickly evolved its Primeknit concept; this allows for a range of fit outcomes, which is a good thing. On one hand, you have the ultra snug fitting Ultra Boost, and on the other hand exists a regular fitting ST.
No
bootie construction like its namesake; the ST sticks to a traditional
lacing design. The first row has a filmic laminate for reinforcement.
See adidas? That wasn’t so hard.
While this is infinitely better than the tortuous experience of the plastic panel used on other models, it isn’t perfect for a few reasons. More on this to follow when we get to the detailed upper fit discussion.
A wide midfoot gusset made of stretchable fabric. Nicely done, ST.
The sleeve stops short of the forefoot inside.
The sleeve starts only after the second eyelet from the rear, which leaves room for the tongue flap.
Here’s the familiar Achilles lip from the UB. That said, the edges of the external plastic heel counter are not quite as tall.
The heel area is similar to the UB’s design, save for a few modifications. The collar opening is wider due to the change in the plastic counter molding design. On the Ultra Boost, the hard component was curved inwards, in addition to being taller than the ST’s counter.
That design variance made the collar opening narrower vs. the Ultra Boost ST, and the shoe ended up being comparatively harder to slide into.
This you might miss during the day…
…but at night, the heel can be a pretty bright place.
Of all the differences in the upper design compared to the Ultra Boost, none is more significant than the one which happens around the toe-box. adidas must have read all the negative feedback around the Energy Boost’s and Ultra Boost’s super pointy toe-box construction, and what happens on the ST is a very welcome change.
There’s a tall stiffener lining the inside of the toe-box.
The Ultra Boost ST has a tall toe-box, with enough room above and ahead.
We haven’t measured, but the ST’s (right) toe-box could be twice as high as UB’s (left).
Needless to mention, the UB ST’s upper fit is very, very different from how the compression loving Ultra Boost fits over the foot. In the front, there is a colossal amount of space, both vertically and around the toes. We thought the day would never come when we would recommend buying a half size smaller in a adidas shoe, but well, what do you know.
If you wear a US 11 in the Ultra Boost or Energy Boost, it should be perfectly ok for most runners to buy a half size smaller (10.5) in the Ultra Boost ST and have little to complain about. On last year’s Ultra, the shallow upper pressed down on the big toe with aggressive stretch force. Nothing of that sort happens on the ST.
As a matter of fact, for the same US 11 size, there was more than a thumb’s width of space right up ahead, a solid justification for buying a half size smaller.
By now, you must have read enough of our reviews to realize that a spacious toe-box isn’t the only factor which affects sizing. The heel design has a say too, and that applies in the ST’s case.
Because of the less aggressive counter molding, the foot sits slightly rearwards on the ST, away from the front. This bears similarity to another knit upper shoe we reviewed last year, the Nike Flyknit Lunar 3.
1) Lots of vertical toe-box space 2) Wide forefoot 3) The ST is easier to get in and out of. Heel grip is slightly compromised.
The plastic cage of the Energy and Ultra Boost is replaced by a relatively pliable synthetic component, so the midfoot fit goes easier on the sides and top in comparison.
The non-stretch nature of the updated Primeknit material ensures that the ‘pinned-down’ feel of the Ultra Boost is kept at bay. What you see is what you get; the upper doesn’t start smaller than your foot size, and then expand once you wear the shoe – we talking about the Ultra Boost.
So when adidas says that the ‘Primeknit upper expands naturally with the foot’, you have to take that with a pinch of salt. They just cut and paste the description from the stretchy Ultra Boost’s product page.
The open collar makes the ST less of a chore to wear.
A minor downside is that the heel doesn’t grip as well as the UB did. That doesn’t mean the heel slides; the grip is sufficient if not tenacious.
1)
No more pressure from the plastic cage 2) The synthetic panel is more
comfortable than its plastic counterpart on the UB 3) Heel counter
height has been reduced and made thinner
If you compared the UB and ST version’s outsole outline, you’ll see that the ST has a much wider midsole waist. The rearfoot area is also marginally wider, though not of the same magnitude as the midfoot.
A wider midsole means that there’s a wider upper atop it, which in turn creates more space. The Ultra Boost ST will come as an unexpected surprise to most who are used to the otherwise narrow fit of adidas models.
The overall situation with the ST’s upper is very positive, except for a couple of blemishes. The top-down pressure over the midfoot is an issue on the ST, though nowhere as acute as how it is on the Ultra and Energy Boost.
A few reasons contribute to this sense of mild discomfort.
Look at the sheer thickness of the midfoot panel eye-stay!
Rigid synthetic reinforcement on both sides. Why? Makes no sense at all.
It is twice as thick as the laminated eye-stay, and rigid as a wooden plank. Even the reverse side of the eyelet area uses a thick synthetic. Why? Does the adidas design team have someone called the ‘midfoot cage director’ whose only job is to take a decent shoe design and ruin it with either a plastic cage or a band of ridiculously thick synthetic?
The Ultra Boost ST’s entire eye-stay could have used the thin laminated material seen on the first lacing row, and by doing so, adidas could have reduced weight and increased fit comfort.
Hey, they should let Kanye West design their performance running shoes. At least the Yeezy’s appear to be free of any midfoot strangeness, and look rather comfortable. What is it with adidas and uncomfortable upper midfoot design?
The space between the lacing is also wide, which translates into a higher degree of top-down pressure. The tongue is padded, but not enough to insulate the lacing pressure from the thin, flat laces cinched over it.
Admittedly, the ST midfoot fits far more relaxed over the foot than the Ultra or Energy Boost. However, run any longer than 10k on the ST, and the stiffness of the synthetic becomes gradually uncomfortable.
It is as if there’s the rest of the Ultra Boost, and then there’s the thick synthetic. Akin to someone putting a dried Chestnut inside your fluffy down pillow. The pillow would be super comfortable, except for the Chestnut and its rattle…
adidas seems to be facing a lot of issues with regards to its production quality. The Ultra Boost ST was purchased along with the Glide 8 Boost and the adios 3 Boost from an adidas store, and it took 10 minutes just trying to separate the shoddily assembled ones from the okay ones. Misaligned upper lasting mostly, which impacts the fit quality in many cases – our Tempo Boost review was proof.
The reviewed pair of Ultra Boost ST looks okay here, because much time was wasted selecting the ‘right’ kind. In all seriousness, it felt like shopping in a factory seconds store.
1)
Forefoot stack heights are taller 2) The medial midsole height is
massive just under the arch 3) There’s more Boost volume under the heel
too.
By default, the wider outsole footprint leads to an increase in the Boost foam volume. Not only that, the stack heights of the ST are substantially higher than that of the Ultra Boost.
By adidas’s own admission (on their product pages), the Ultra Boost ST has front and rear midsole heights of 32mm and 24mm respectively. In comparison, the non-ST model has 20.5 mm of forefoot height and 30.5 on the heel.
To summarize, the ST model reviewed today has a wider and taller Boost midsole than the UB. And if you haven’t figured out the maths already, the ST has a 8 mm static drop vs. 10 mm of the UB.
What adidas doesn’t tell you that the ST’s medial Boost midsole is massively higher than the standard UB’s. Just under the arch, the height of the ST midsole is a whopping 7 mm taller . And this is the means by which the ST delivers a higher level of under-arch support.
The densities are the same on the medial and lateral side; the only difference is the height of the sidewall, and the translucent support overlay made of flexible urethane.
The cool looking medial band – how does it function, if at all?
Before getting into the specifics of the urethane overlay’s dynamics, we need to explain how the Ultra Boost ST’s foam midsole actually works from a motion control perspective.
This
is how the ST justifies its categorization. The medial side is
significantly taller than the lateral, and especially more so than the
stock Ultra Boost.
Hence the Ultra Boost ST intends to control inward foot-roll by means of a midsole design which has more material under the arch side than the other side.
However, instead of doing so through a softer foam on the lateral side and a firmer foam on the medial side (also called the adidas pro-moderator construction on older models), the ST aims to deliver a motion control outcome by making the medial side more cushioned .
The effect of this unique design is quite mild. You do get this sense that there’s more foam under your arch, which actually feels quite nice. The softness of the Boost foam ensures that there’s no poke-yness.
This is not a stability or a support shoe by any standard; if anything, it is a very benign motion control shoe. It does not have any of the firmness expected of a conventional stability shoe. adidas calling the ST a stability shoe is a misnomer – this one is not.
So coming back to the original question – what exactly that does see-thru polyurethane do?
The correct way to address that question would be – what would happen if that ‘Energized stability’ component did not exist?
A high volume Boost foam midsole when left completely to its own devices, is a stability disaster. Most Boost shoes have a stabilizing rim over its midsole , or is augmented with a support casing . Without any of these support mechanisms, the midsole will simply collapse under body weight or footstrike.
Boost midsoles are ribbed or terraced to make the foundation more stable.
Given that context, the Ultra Boost ST with its extremely high medial sidewall, desperately requires a support structure. This is where the translucent green overlay comes into the picture.
It’s function is to contain excessive compression or sideways shear, and potential collapse/splaying out of the soft Boost foam. The motion control part is achieved by the beveled midsole with its higher medial sidewall; the urethane strip’s only job is to maintain the integrity of that structure and function.
It might not be a medial post in the known sense of the word, and yet it has an important role to play in the bigger scheme of things. It is certainly not a mere decoration.
The translucent urethane prevents the Ultra Boost ST from turning into a Pure Boost, and that is good enough a reason for its existence. It must be noted that this strip is flexible, so it bends with the Boost foam instead of sticking out as a hard support structure.
In a nutshell, the ‘Energized stability’ piece exists to make up for the shortcomings of the otherwise excellent Boost foam.
The
Torsion plate extends till the medial heel and joins the green Urethane
above it. The outsole rubber tends to shred faster under this hard area
if loaded.
As a side note, the outsole tends to wear off faster just under the area where the Torsion plate meets the Urethane strip. A harder outsole there means more pressure on the soft rubber, and hence the wear.
With all the added foam material, the Ultra Boost ST ends up being a highly cushioned shoe. It is the most cushioned within adidas’s existing performance running line-up, the standard UB included. There are no firm rims or casing restricting the midsole, so the ST delivers an unadulterated Boost ride experience.
The UB ST comes assembled with a thick EVA sockliner.
The thin, perforated textile lasting offers a near-direct access to the Boost midsole underneath.
And if you must know, the ST’s sockliner is different from that used inside the Ultra Boost.
The ST’s insole edges rise up on the sides.
As far as the ride experience goes, it is very soft, but without the mushiness of EVA midsole based models such as the Asics Nimbus 17. There is a level of responsiveness typical of adidas Boost; however all the cushioning depth gets in the way of a speedier ride.
The best way to describe the ride experience is that the ST is very well cushioned, and feels neither slow nor fast. The transition quality is also a mite lazy due to all the foam, but at the same time you don’t get the feeling you’re walking around in a pit of molasses either.
What the ST does better over the standard Ultra B is in the quality of cushioning spread. With the forefoot being significantly jacked up in terms of stack heights, the cushioning quality feels balanced, more evenly distributed. This has no negative impact on forefoot flexibility – the ST remains super bendable in the front.
The regular UB in comparison felt a bit rearfoot loaded due to its lower forefoot midsole height. The ST also feels more planted than the UB, which is a natural byproduct of its wider outsole footprint.
One would imagine that the ST would be very heavy with the over-sized Boost midsole, but you know what, it does rather well in the weight department. A US 11 weighs a shade over 350 gms/12 Oz, which isn’t bad considering the midsole is full length Polyurethane – which weighs more than EVA.
The ST is only slightly heavier than the Glide 8 Boost, which makes its bulk tolerable. Understandably, the increase in midsole volume and outsole rubber makes the ST around 20 gm/0.7 Oz heavier than the stock Ultra.
In more ways than one, the ST is a marked improvement over the standard Ultra Boost. There’s much more upper room, the plastic prison is gone, the sole grips better, and the cushioning experience is more balanced. Much like the Brooks Transcend 3, the ST is one shoe which performs the role of both a neutral and mild motion control shoe equally well.
There is some chatter about the Ultra Boost ST being a replacement for the adistar Boost. We haven’t reviewed the adistar Boost, but from the looks of that shoe, it should have a much firmer ride, a noticeable degree of medial side support, and a tight upper fit resulting from the use of stretch ESM or techfit upper.
If what we’re assuming is true, then runners seeking to switch from the adistar Boost will be disappointed by the ST’s easy upper fit and neutral ride aspect.
On the other hand, if you were considering getting the regular Ultra Boost, then we suggest that you buy the ST instead. Do not worry about the shoe’s ‘stability’ pretensions, the ST is no more of a stability shoe than the UB is.
The shoe delivers a ride experience with a strong neutral vibe, the exception being the additional soft filling under the arch. Conversely, if you’re shopping for a shoe with a firm and supportive ride (adistar users, listen up), then we’d like to point you in the direction of the adidas Sequence Boost 8.
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