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Road Running Shoes • January 18, 2024

Brooks Glycerin 21 Review: Lofty Ambitions

feature photo of brooks glycerin 21

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What You Need To Know


9.8 oz. (277 g) for a US M9,

8.8 oz. (249 g) for a US W8

Stack Height / Drop

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

Best For

Casual, well-padded recovery miles

Key Features

RoadTack rubber outsole, Additional 2 mm of DNA Loft v3 midsole foam, Engineered Warp Knit upper

On The Run
Plenty of cushion for the pushin' Much-improved outsole layout Literally impossible to achieve lockdown with all this cushion


Introduction to the Brooks Glycerin 21

KALEB: I’m not usually one to hold grudges. Heck, if I get heated with someone, I probably won’t even make it into the double-digit hours before I’m back and trying to reconcile the situation. I’ve got limited time on this earth, and I don’t want to waste it fueling petty frustration.

But some hurts run too deep for “forgive and forget.” Like when someone eats the last blueberry bagel, convinces you to spell icup, or tells you that orange spelled backward is gullible. Or slashes your tires and keys your car — stuff like that.

Brooks earned itself a grudge from me almost exactly one year ago with the release of the Levitate 6. Though I attempted to temper my review and be fair to external factors, the bottom line was that the shoe sucked enough to aggravate my first significant running injury in twelve years.

Since then, I’ve consistently ripped on Brooks at every opportunity for marketing bricks with laces. And to be fair, Brooks has made it fairly easy. It may have its shoes on the feet of a huge number of runners, but shoe nerds will typically make a face if you tell them the Brooks Ghost is a sexy piece of footwear and you’re not going to see a bunch of runners in the Hyperion Elite at any local races.

And yet…

Slowly, and none too surely, Brooks has begun to move like some ancient, long-slumbering beast awakening. Or a college student getting up for an 8:00 am class. The point is, there are, at last, some signs of Brooks adapting its footwear to catch up with the cool kids.

The Glycerin 21 is the top of the “cushion” branch at Brooks, hitting the scene as a mid-stack, max-comfort trainer. Two more millimeters of DNA LOFT v3 foam underfoot, a brand new upper, and a solid coat of Brooks’ new RoadTack rubber make up the updates of the 21st version.

Even on paper, things could go either way, so my question going into this review was simple: is my grudge against Brooks still justified, or is it at last time to let bygones be bygones?

LINDSAY: Just when I start thinking I need a max-plush shoe for all of my long and easy runs, along comes the Brooks Glycerin 21 to change my mind. Some would call this a “max cushion” daily trainer, but with all the cushioned options out there now, this just isn’t in that category. Daily trainer, yes. Max cushion, no. Optimal cushion daily trainer? Brooks Glycerin 21.

This shoe comes in four (!!!) different iterations, but I’m just going to focus on the tried and true OG version. See our other reviews for the GTS, Stealthfit, and (you guessed it) GTS Stealthfit. I’m really curious how different they all are, so hopefully someone got to run in all four, but I digress.

The Brooks Glycerin 21 for women comes in an array of colors that is honestly the most all-inclusive I’ve seen in a while, and I love it. You’ve got your solid black and solid white, the Zebra (black and white), pink, navy blue, and a couple of mixed fellas, one of which will make all the fluorescent colorway connoisseurs happy and the other a little more tame.

Enough about the appearance, though. Let’s talk about what’s really important in this world, and that is what’s on the inside. Amiright?

What we like about the Brooks Glycerin 21

KALEB: Starting up top, the Glycerin 21’s warp knit upper sets the tone of the shoe: comfort without excess. The material feels luxuriously soft, and it has the perfect balance of security and give for an easy daily trainer. The laces are of similar quality: soft and stretchy enough not to bite the foot but secure enough to keep you from sliding around on the go.

Both the collar and tongue are cushioned, but they don’t stuff the foot into a mattress like some plush uppers. Overlays are an underrated part of a shoe’s upper. Not because they’re vitally important but because when they are present, they have a lot of potential to add to or completely mess up the upper security and comfort. I found that the few overlays present on the Glycerin 21 did their job admirably and accentuated the soft, comfy lockdown.

This was my first experience with DNA LOFT v3, one of Brooks’ two supercritical foams, and it was a pleasure. On the run, it has the perfect squish-to-bounce ratio for an easy day trainer. Yes, that’s right, I enjoyed the ride of a Brooks shoe. Despite the not-so-maxed-out stack height, the shoe rides like a max cushion trainer. Something that Robbe has noted in the past is that plenty of shoes that look max-cushion on paper don’t feel soft and comfy on the roads. The Glycerin 21 does the opposite: a 28-18 mm stack (midsole only, so technically, it’s a bit taller than this) ain’t nothing in a timeline where the Adidas Prime X Strung exists, yet the ride feels soft and stable like a max-cushion shoe should. Whatever is in DNA LOFT v3 besides Nitrogen, it works.

brooks glycerin 21 - insole

The overall geometry of the Glycerin 21 is a bit reminiscent of the Ghost Max with its wide base, secure heel, and dramatically rockered toe to help keep the comfort cruising forward. While the Glycerin 21’s use case is definitely not uptempo, I didn’t feel like I was stuck in a single gear, either, and I think that rockered forefoot was a main contributor to that fact. I think another significant factor was the rubber coverage.

The previous Brooks shoes I’ve reviewed have all had a more or less fully covered outsole. While this is a plus for durability, I think it often tamps down the ride personality of a shoe. The rubber placement on the Glycerin 21 is still widespread enough to offer solid durability, but the fact that it is separated into segmented pods throughout high-wear areas allows the DNA LOFT v3 to compress and work its magic rather than be trapped behind a slab of rubber. Plus, less rubber coverage means that, despite the 2mm midsole increase, the shoe loses weight from last year’s version, coming in at a very reasonable 9.8 oz for a US M9.

One last plus for the Glycerin 21: it’s not ugly as all get out! Obviously, this comes down to personal preference, but both the colorway and midsole tooling of this shoe look clean and modern, which is a far cry from the Brooks shoes of the past few years.

LINDSAY: The Brooks Glycerin 21 has a warm, knit upper. I don’t mean like the UA HOVR Mega warm, but you’re not exactly feeling the breeze between your toes in the Glycerin. I kept this under the positives because we’re in the winter months, and any little bit helps. In addition to being knitted and durable, the upper is also delightfully plush. I know I said this shoe wasn’t a max-cushion shoe, but when it comes to the tongue and around the ankle, it’s a literal pillow. Very comfortable. That also goes for the roomy toe box. No unhappy bunions here.

The midsole is Brooks’s third version of the DNA LOFT foam, which is the same foam that was in the Glycerin 20. This time, however, we get a little more of it — 2 mm, to be exact. This felt really balanced underneath my feet, which made for a productive push-off with each stride. I would probably also attribute this to the fact that I did not experience any soreness (aka shin splints) while trying a new shoe, which is rare for me.

The outsole is a nice wide platform of Brooks’s new RoadTack rubber. No added weight there, and it’s quite durable, with good traction on wet roads.

Shop Brooks Glycerin - Men Shop Brooks Glycerin - Women

What we don’t like about the Brooks Glycerin 21

KALEB: Call me old fashioned (actually, call Brooks old fashioned, call me preferences), but the 10 mm drop is just… a little too much. Running in the Glycerin 21, I felt a little obligated to tend towards a heel strike rather than my typical forefoot strike. I was still able to maintain good form, but the drop definitely caters to a heel-striking audience. I don’t know why Brooks sticks to such a high-drop norm across their line when mid-to-low drop options would be more accessible and would promote healthier form for runners.

Other than that, I think Brooks has really done a solid job on this iteration of the Glycerin; it accomplishes what it’s advertised as, and that’s a far cry from… past experiences with the brand.

LINDSAY: The upper, being as soft and cushioned as it is, makes it hard to get a good lockdown with the laces. I had to tighten them quite a bit to feel secure, but at least you know you’ll never over-tighten them.

I’m also a sucker for bouncy, responsive shoes, and this was just… not that. While the Glycerin 21 is a smooth ride through and through, it doesn’t have the pop and energy return of, say, the Asics Superblast. It’s not necessarily a bad thing, but just worth mentioning if you’re looking for that characteristic.

Shop Brooks Glycerin - Men Shop Brooks Glycerin - Women

Brooks Glycerin 21 Conclusion

KALEB: Healing is a process, not an overnight miracle. So, while I’m not completely willing to let Brooks’ old water run away under the bridge, the Glycerin 21 gives me hope that one day — one very distant day — I might walk past a running store and say, “Oh boy, I wonder what Brooks has got cooking up.” This is a shoe that I’ll definitely keep coming back to lace up again and again.

While trainers like the Ghost Max were exciting signs of change for Brooks, the fact that those changes are leaking into a mainstay line like the Glycerin is a quieter yet equally significant sign that perhaps Brooks truly is turning over a new leaf across the board. And while I can’t erase past wrongs, I suppose I can’t begrudge new beginnings either, so best of luck in the new year, Brooks.

brooks glycerin 21 - outsole

LINDSAY: I can see now why this is one of Brooks best selling running shoes. The Brooks Glycerin 21 gives the perfect balance of a soft, step-in-ready shoe while still being able to feel the ground under your feet. It’s a comfortable ride for everyday training runs, and it’s affordable(ish). Double win. It reminds me a lot of the Saucony Triumph 21, and just like that shoe, I would definitely recommend the Brook Glycerin 21.

You can pick up the Brooks Glycerin 21 for $160 at Running Warehouse (featuring free 2-day shipping and 90-day returns) using the buttons below.

Shop The Shoe


Shop Brooks Glycerin 21 Men
Shop Brooks Glycerin 21 Women

Have something to say? Leave a Comment

  1. Peter M says:

    Per the stack on the Glycerin is 38/28

    1. Robbe says:

      These are directly from Brooks and doesn’t include insole and outsole measurements, also Running Warehouse is not always correct

  2. Terry Reilly says:

    “UA HOVR Mega warm”…had to google that! Also, I cannot figure out why running shoe companies feell obligated to make “stealthfit” versions of shoes. Way too often customers are uneasy with the look and fit, however unreasonable that objection might be. We never carry stealthfit shoes when another standard fit it available.

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Kaleb Kabakjian
Track and XC Reviewer

Kaleb is one of the younger, “both of my knees still work” reviewers on the BITR team. As a high school cross country, track and field, and road racing athlete in Pennsylvania, Kaleb loves hearing about the latest endurance-athletics studies and seeing how everything out there can fit into a well-rounded training program. If you don’t see him drinking a weird health concoction or doing some strange warmup technique, he’s probably already started the race.

All-time favorite shoes: Saucony Ride 14, Nike ZoomX Dragonfly

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Fav. Distance

1 Mile

  • 1:18

    Half Marathon
  • 16:14

    5K (XC)
  • 4:30

  • 2:03

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Lindsay Agro
Baltimore Road Reviewer
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Lindsay is an optometrist by day and runner by… all other hours. Originally from south Florida, Lindsay started running with Believe Run Club when she moved to Baltimore and the rest is history. When she’s not running or fixing eyeballs, you can find her exploring with her dog, Iris, or grabbing a beer with friends.

All-time favorite shoes: Asics Novablast, Saucony Endorphin line, Nike Vaporfly NEXT%

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Fav. Distance


  • 3:35

  • 1:42

    Half Marathon
  • 44:52

  • 22:08

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