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Road Running Shoes • February 12, 2024

Brooks Glycerin GTS 21 Review: A real Go-To of a Shoe

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What You Need To Know


10.5 oz. (297 g) for a US M9,

9.2 oz. (261 g) for a US W7.5

Stack Height / Drop

28 mm in heel, 18 mm in forefoot (10 mm drop, midsole measurement only)

Best For

Stable miles at a relaxed pace

Key Features

Roadtack outsole, DNA Loft v3 midsole, Guiderails for support, engineered warp knit upper

On The Run
Warp knit upper is extremely comfortable DNA Loft v3 has plenty of cushion for cruisin' An exciting ride, this is not


Introduction to the Brooks Glycerin GTS 21

SAM: Do you ever have one of those moments in the middle of the day, whether riding the bus, sitting for a job interview, or presenting in a meeting, when you think of one of those highly embarrassing things you did when you were younger? You know, the ones that fill you with shame and anxiety? For most people, it’s usually something like their pants ripping, an awkward interaction with a stranger, or maybe forgetting their wallet at the grocery store.

Because I’m weird, one of those moments for me is the stinging memory that I wore the Brooks Glycerin — and only the Brooks Glycerin — during my freshman year of collegiate track. What on Earth was I thinking? I was wearing an absolute brick of a shoe for 400-meter repeats and hoping to impress my new teammates purely based on my work ethic.

Thankfully, D3 track eventually gave me the room to experiment, learn, and understand what shoes belong in a running rotation. Maybe that’s the true benefit of a liberal arts education. Anecdote aside, it’s been a few years since that shoe, and the Glycerin has undergone some changes. Although this is the GTS version, I still hoped that the Glycerin had lost some weight and gained some bounce over the years.

Will my core memory be put to rest? Can I finally move beyond my freshman year of college and let the pain of embarrassment fade into an acceptance of my human need to grow and learn? Let’s find out.

AUSTIN: In retrospect, I’m surprised that I reached for the Brooks Ghost Max ahead of every long run in my buildup to the Rocket City Marathon last December. What can I say? I loved that shoe — something I almost never say in the same breath as the word Brooks.

Now, my Ghost Max is within about a hundred miles of total midsole demise and subsequent recycling at a local running shop. I don’t mind, though, the shoe delivered as a trusty daily trainer when I needed it to. Unfortunately, my next pair of Brooks, the Glycerin GTS 21, probably won’t be getting the same star treatment. I can already tell you that it won’t usurp the Ghost Max as my new beloved trainer for the spring build, but there’s still some good stuff to unpack.

What we like about the Brooks Glycerin 21 GTS

SAM: Thankfully, the Glycerin 21 GTS has a lot going for it as a tried and true stability trainer. There are two things to focus on this shoe, and that is stability and comfort. If you have read any of my reviews before, you may know that I love the Guiderails, and they do not disappoint here. I often seek out innovation in new shoes, but Brooks is the definition of if it ain’t broke, don’t fix it.

The Guiderails remain my favorite stability technology, and they provide streamlined support that adjusts to your stride and your bio-mechanical needs over time. I also love the width of the shoe and the 10 mm drop, which combine to give the shoe a quick heel-to-toe transition that stays centered. The drop, build, and Guiderails give this shoe stability that you do not need to think about, which is exactly what I like in a shoe.

As far as comfort goes, the Glycerin 21 GTS is a big improvement from previous models. The main change this year is the engineered warp knit upper. According to Brooks, it’s designed to be flexible, accommodating, and soft, and I would argue that it achieved this goal. I have a slightly wider than normal foot and had no issues at all with hotspots. Sometimes, these softer uppers can become too sock-like and get hot, but I had no issues in the constantly changing Baltimore weather.

The other comfort feature in the Glycerin 21 GTS is the DNA Loft V3 midsole. This is the second iteration of this shoe with this foam, and I would say that it is noticeably softer than other Brooks models. This does detract somewhat from the response of the shoe, as I will discuss later, but combines with the upper for a cohesive, comfortable, and supportive experience. In a world where comfort and stability are the prize, the Glycerin 21 GTS takes first place.

AUSTIN: I haven’t run in the Glycerin in several years, but I like what I see in this version. According to Brooks, the company added two millimeters of DNA Loft v3 to soften the ride. So far, the step-in comfort, which I regularly mention in Brooks reviews, shines.

There’s ample room in the toe box courtesy of the engineered warp (sounds like a phrase from Star Trek) knit upper; the tongue and heel collar provide ample padding; and the midfoot lock feels secure despite the absence of a gusset. The shoe fits true to size, and the upper feels great against the foot. Durability should be solid, too, thanks to a RoadTack outsole configuration.

One other noticeable design change centers around the Guiderails. In the Glycerin GTS 20, the Guiderails seemed to stick out from the midsole, but on the Glycerin GTS 21, they appear (and feel) flush. I know this is trivial, but visually, I try to catch the smaller details in updates. Also, like the Glycerin GTS 20, the ride lands in the middle of soft and firm. There’s a modest bounce, but I’m not amazed. You know what to expect with a Glycerin — a daily trainer with modest cushioning and a ride that skews firm.

Shop Brooks Glycerin - Men Shop Brooks Glycerin - Women

What we don’t like about the Brooks Glycerin GTS 21

SAM: If you are looking for a stable, comfortable shoe, the Glycerin 21 GTS is a great choice. However, if you want a shoe that’s exciting to wear, the Glycerin 21 GTS isn’t a great choice. Our current working theory is that the DNA Loft v3 in this shoe is not the same as the standard model, which is not also the same as the Aurora-BL, where it made its debut. While soft, the midsole in this shoe lacks any real zip or bounce to it. I kept reaching back for the shoe because of its comfort, but I was never excited to run in it.

Brooks’s bread-and-butter shoe design for a while has been firm, dense, and low-stack shoes that are responsive solely due to their lack of foam but are more durable than your average trainer. The Glycerin 21 GTS sticks to that formula with a paltry 28 mm in the heel and 18 mm in the forefoot. When I hear about a soft and cushioned shoe, that’s not at all what I think.

Maybe it fit the bill 10 years ago, but not now when stability trainers around the same weight (10.5 oz.) have nearly 10 mm more stack height to play with. This wouldn’t be a huge issue if the Glycerin were as firm as it used to be, but now that it is softer to run in, it just feels bland. The Glycerin 21 GTS will feel the same after 300 miles as it feels after three, which is an overall positive, but at no point will you look down at your watch and be surprised at how fast you’re running.

AUSTIN: I don’t have much to gripe about, but I would like to see two changes in Brooks footwear in the coming years: less weight and lower drops. I’d like to see the Glycerin of the future shed an ounce of weight and probably about two millimeters from heel to toe.

Of course, these are preferences based on my footwear proclivities, but high-drop shoes throw off my motion path, and heavier shoes can feel like anchors during long runs. Still, the Glycerin GTS 21 performed well during my miles. I stuck with easy paces and distances, but I know it would be an excellent choice for long runs, too.

Shop Brooks Glycerin - Men Shop Brooks Glycerin - Women

Final thoughts on the Brooks Glycerin GTS 21

SAM: Overall, I have to say that this is a solid stability trainer. It’s the pinnacle of stability technology and has comfort that will last a long long time. But, with that said, don’t let good be the enemy of great. This shoe lacks the oomph that I wish it had, especially after how much fun our reviewers had running in the Aurora-BL a few years back. Hopefully Brooks can add some of that shoe’s punch to future models of the Glycerin without sacrificing its efficacy as a stability trainer. Brooks is moving in the right direction but still has a way to go.

AUSTIN: After a lengthy absence, I enjoyed running in the Brooks Glycerin GTS 21. Though I don’t need the Guiderails, their presence felt quiet — there if you need them without feeling invasive. Between the knit upper, DNA Loft v3 midsole, and Roadtack rubber outsole, this model will last many, many miles.

Oh, and one of the colors in the shoes I received is Nasturtium. I had to consult Google about that one, but it turns out it’s a flowering plant. Does Brooks consult with horticulturists on color choices? Intriguing.

You can pick up the Brooks Glycerin GTS 21 for $159 at Running Warehouse (featuring free 2-day shipping and 90-day returns) using the buttons below.

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sam sheldon3
Sam Sheldon
Baltimore Road Reviewer
  • Strava

Sam tried every other sport before settling on running as a senior in high school. He’s never looked back. He can be found doing workouts in Patterson Park, talking shop with the Faster Bastards, or hitting long runs on the NCR trail. When not running, Sam is a teacher in the Baltimore City Public School District. His other loves are cooking, coffee, breweries, books, basketball, and alliteration. 

All-time favorite shoes: Saucony Endorphin Speed 2, Nike Vaporfly Next%, Asics Novablast 3

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Fav. Distance


  • 2:54

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  • 14:58

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austin bonds
Austin Bonds
Southern Road Reviewer
  • Instagram

Austin, who lives north of Atlanta, is a stay-at-home father and running store part-timer (year eleven). Based on his inability to provide a 10K or 5K personal record, he should probably race those distances more. It’s rare to not see a party size bag of peanut M&Ms in his pantry and a pair of Shokz on his ears during a run.

All-time favorite shoes: OG Altra Escalante, Saucony Kinvara 3, Nike ZoomX Vaporfly NEXT%

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  • 3:03

  • 1:25

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