| PROS | CONS |
|---|---|
| + Light daily trainer + Decoupled heel + Flexible & adaptable + Comfy, airy sock-upper + Least expensive Glycerin | – None |
The Flex is the latest addition to the Glycerin lineup, joining the likes of the Glycerin Max, Glycerin GTS, the standard Glycerin, and the Glycerin Pro. Find out how it stacks up against the other Glycerins (Glycerini?), in this Brooks Glycerin Flex review. Oh, and I made up the Glycerin Pro.
Introduction
It’s unbelievable a shoe named “Glycerin” has made it this far. Most people couldn’t even tell you what Glycerin means. Hell, I had to look it up myself and I’m still not quite sure. We’re on the 23rd version of the OG Glycerin which has spawned four three other variations (so far); a rate of innovation that was unthinkable for Brooks a mere five years ago. You have to commend them for being willing to experiment time and again.
Brooks markets the shoe by so boldly daring runners to “flex the rules” — not to be confused with the superior act of breaking the rules. The rule in question? Making a shoe’s outsole the most exciting feature of a shoe. Now, that is bold. And with it, Brooks breaks the mold of the typical outsole.
The figurative price tag “on top” of the shoe is pretty appealing, too. At $170, it’s the cheapest least expensive in the Glycerin line.
Brooks Glycerin Flex Review
| STACK | WEIGHT | PRICE |
|---|---|---|
| 36/30 mm (6 mm drop) | M9: 9.1 oz/258g) W8: 8.0 oz/(227g) | $170 |
Outsole
This is truly unprecedented! No one ever starts a shoe review with the boring, inconsequential outsole. I mean, it’s the one part of the shoe you can’t see while running. Like, a typical outsole is about as exciting as going running with your parents. Sure, it’s quality bonding time, but it’s monotonous as hell. “Can we pick up the pace a bit, guys?” You’re better off just running alone.
But the Glycerin Flex may just be the first shoe with an outsole that actually matters. I’m exaggerating, of course, but it’s definitely the first outsole to write home about — as if people still write home in this day and age. Hell, people don’t even write anymore, thanks to AI. Nor do they read — also thanks to AI. Which begs the question: why am I even writing this review? Clearly, no one’s going to read it. Frankly, I might not even read it.
Brooks’ FlexZone™ aka the significant midfoot flex grooves (I’ve never seen flex grooves this deep), and the podular decoupled heel design provide a great amount of flexibility upon landing without being unstable. As Brooks says, the FlexZone “helps facilitate the body’s preferred motion path.” Put more simply, it promotes more natural movement, adapting to the runner’s stride. And it works! Each landing feels smooth and contours well to both my heel and midfoot strikes.
The outsole really makes this shoe, and it’s arguably what elevates the Flex above the Glycerin 23 and Glycerin Max 2.
Notably, this isn’t the first time Brooks has done a decoupled outsole. That’s right: way back in 2021, Brooks had a limited release of the excellent Aurora-Bl. The lightweight and responsive pair flew under the radar for most, but is one of my favorite Brooks pairs ever. You could say the Aurora-BL walked so the Glycerin Flex could run.
Midsole
No surprise here: all the Glycerin versions have Brooks’ dual-density DNA TUNED in the midsole. The nitrogen-infused foam has larger cells in the heel for softer landings, and smaller, more densely packed cells in the forefoot for enhanced responsiveness. DNA TUNED is lighter and provides better energy return than the nitrogen-infused DNA LOFT v3 found in the Ghost 17 and Ghost Max 3.
At 36 mm /30 mm (6 mm drop), the Flex has just a slightly shorter stack height (and heel-toe drop) than the Glycerin 23 (38 mm/30 mm). The Glycerin Max 2 is the tallest Glycerin —and Brooks shoe— at 45 mm/39 mm.
When it comes to the Glycerin, less foam is more. I find myself preferring the Flex’s more moderate stack height (relatively speaking) to the beefy Glycerin Max 2, which can feel a bit clunky at faster paces.
Ride
With a heavier weight and hefty outsole rubber, the standard version of the Glycerin has never been known as a versatile shoe. But with the Flex, it’s easy to both accelerate and take it easy when you want. And there’s a high comfort level. The combo of DNA TUNED and the FlexZone pair well for a ride that’s suitable for runs of any distance.
The Flex has a softer underfoot sensation than both the firmer Glycerin 23 and Glycerin Max 2, and feels more responsive, to boot — uh, and compared to a pair of boots, I suppose. Mushy landings are usually as hated by runners as hotel bed bugs the night before race day, but I love the slight “spongy” sensation I feel from running in the Flex. While not super bouncy, DNA TUNED provides a solid level of energy return, more noticeably in the Flex.
With a great weight for a daily trainer (9.1 oz for men’s size 9 and 8 oz for women’s size 8) and a flexible outsole without a shit ton of rubber, the Flex provides a very versatile ride. This will serve as an excellent daily trainer, easy day shoe, and long run option for many.
Not too high or low, the inclusive 6 mm heel-toe drop is well suited to many runners, regardless of foot strike. And it works especially well with the dual-density DNA TUNED foam. Depending on pace, I alternate between heel and midfoot strikes in the shoe without a hitch. While there’s no Glideroll rocker geometry like in other Brooks pairs, heel-toe transitions feel incredibly natural, and every stride feels smooth.
Upper
One of the best-fitting, comfiest uppers from Brooks in some time. A knit, sock-like upper provides a great amount of comfort for miles on end and there are ample ventilation holes to help your feet breathe. It’s also translucent: you can see sunlight pass through the rear of the shoe. This soft upper fits nice and snug without suffocating my feet. There’s a padded heel collar that enhances comfort and helps keep my feet securely in place. The minimal, non-gusseted tongue is quite stretchy and loose, but still ensures an optimal foot lockdown.
With a nice-sized toebox, there’s enough room for my toes to spread out as they need; no small feat, as my gargantuan toes more closely resemble the size of fingers on most hands. Yeah, I’m a freak. Unfortunately, what they say about guys with big feet is a myth; I had to learn that the hard way. At least I’ve got a big heart?
Weight
With the comfy, padded upper and decent stack height, I’m surprised Brooks can get this shoe so light. It’s an exceptional weight for a shoe of this nature. Again, the innovative outsole design and minimal rubber greatly help here. The knit upper also sheds weight.
At 9.1 oz (258 g) for a men’s size 9 and 8 oz (227 g) for a women’s size 8, the shoe is a considerably 1.5 oz lighter than the Glycerin 23 and 2.2 oz lighter than the Glycerin Max 2. Just imagine how much lighter it’d be without that ridiculous pull tab on the heel!
Aesthetics
With its funky-looking midsole and outsole design and minimal upper, the Flex is much more visually striking than the Glycerin 23, especially with the 23’s underwhelming men’s colorways. Seriously, what were they thinking with these? I get that they release more colorways later, but you’ve got to start with at least a couple palatable options. Running is nothing if not a fashion contest!
Price
The least expensive Glycerin at $170, the Flex is $5 cheaper than the Glycerin 23 ($175) and a whopping $30 less expensive than the Glycerin Max 2 ($200). A good value for a shoe that should provide excellent durability, as is typical of Brooks.
Conclusion
The Glycerin Flex is exactly as its name suggests — in more ways than one. Boasting an innovative decoupled heel and significant midfoot flex grooves, the shoe adapts well to a runner’s natural movement, providing significant flexibility. It’s also a “flex” for Brooks, who continues to innovate their shoe lineup with positive results.
Hard to find anything to dislike, the lightest and least expensive Glycerin may just be the best Glycerin. With immense comfort from top to bottom, it can go the distance.
The Glycerin Flex is available on Brooks’ website…or pretty much anywhere.
Brooks graciously provided this shoe to me for wear testing. I was not compensated for this Brooks Glycerin Flex review and they didn’t get an opportunity to see this Brooks Glycerin Flex review before I published.
This post includes affiliate links, which means I may earn a small commission if you purchase using the links (at no extra cost to you.)
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