Brooks Glycerin 21 Performance Review

Annie: The nitrogen-infused, DNA Loft v3 that comprises the midsole of the Brooks Glycerin 21 is among my most trusted foams for daily miles. I loved the DNA Loft v3 that debuted in the Brooks Aurora-BL and the DNA Loft v3 found in other Brooks shoes that weren’t even my cup of tea (for reasons that had nothing to do with the midsole material). While the exact feel of the foam can vary with how it’s tuned and implemented from shoe to shoe, it’s a reliable performer that seems to agree with me.

So, when the Brooks Glycerin 21 magically appeared on my doorstep, I had reasonable hopes that it could become a go-to when my body might need a reset (or, to steal Drew’s apropos term, I thought it could become a “palate cleanser” shoe).

Drew: I’ve been a Glycerin fan for several years now (basically since the switch to DNA Loft v3) and the Glycerin 20 was a shoe I kept using from time to time even after I finished testing them, usage I reserve for top tier running shoes that work great for my feet. 

So like Annie, I was pumped to test another Glycerin. Each year I’ve tested the model it’s improved, not by leaps and bounds, but with little tweaks that make it better and keep it fresh. I’m rubbing my hands together to see what improved this time.

Tyler: Stepping into the Brooks Glycerin 21, I was excited as last year’s 20 was a solid shoe that did a lot right (at the time, I tested the Stealth version, which left a little to be desired from an overall fit standpoint). 

I was glad to get the “normal” version, and while Brooks is not known to be on the flashier side of aesthetics or design approaches, initial impressions were strong. But unlike Annie and Drew, I have a feeling that my experience with the Brooks Glycerin 21 might not be as positive as theirs.

Midsole

Annie: I don’t tend to experience DNA Loft v3 as “super-soft” (as Brooks indicates), at least not in the sense of the overt squishiness you’ll perhaps find in something like the Asics Gel Nimbus 25 (or 26). But I would describe the Brooks Glycerin 21’s midsole as extremely comfortable, resilient, and unbelievably consistent. Brooks does hit the nail on the head with its claim of “a distraction-free ride.”

I was able to displace just enough of the DNA Loft v3 to feel its protection but never get lost in it. That measured response makes the Glycerin 21 both a fantastic option for easy daily miles and an enjoyable long run companion that won’t feel like you’re lugging it around after a couple of hours on the road. I found myself looking forward to lacing it up because I knew it would treat me well. A daily trainer is indeed doing its job when I can confidently predict how recovered I’ll feel after running in it – and I always felt pampered by the Brooks Glycerin 21.

Despite having the same 10mm drop as previous versions, the Glycerin 21 felt smoother overall and the forefoot slightly more inclined to turn over at a modest clip. I don’t know if Brooks has directly made changes with regard to the rocker geometry (other than the 2 mm increase in stack height, of course). But for whatever reason, the ride felt more efficient and naturally suited to my gait than I sometimes find with other shoes with a similarly high drop. I suspect the outsole played a role in this as well, but more on that later.

In the meantime, I’m curious as to what Tyler and Drew thought of the ride, especially because they’ve both logged significant miles in last year’s Brooks Glycerin 20 for comparison. So, how did you two find this midsole setup?

Drew: For me, the redesigned midsole shape with its undulations, was a nice modernization in the aesthetics department. Underfoot, I felt the extra 2mm of DNA Loft v3 as a touch of extra plushness. The stack measurements still aren’t high by modern standards at 28mm in the heel and 18mm in the forefoot, but the Brooks Glycerin 21 stacks up nicely against other shoes meant for easy miles.

And it’s got some versatility as the DNA Loft v3 is bouncy and delivers a little bit of speed for pick me ups along the running route. Want to absolutely crush the upcoming hill? The Brooks Glycerin 21 can dig in and speed up in a way many daily trainers can’t. Now, the Glycerin 21 will still feel sluggish for track intervals or sprints, but throwing some tempo work into a long run is well within its capabilities.

Tyler: No doubt, the DNA Loft v3 feels good – really good, in fact. From the initial try on to putting some slower and longer miles in the shoe, it had such a consistent ride that I remember so distinctly from the Glycerin 20. The 10mm drop didn’t feel as noticeable as I was expecting, but toe off is where I found myself wanting more. 

I think the biggest complaint I have is the lack of forefoot cushioning (or noticeability between the heel and forefoot cushioning) in comparison to the plushness of the rest of the shoe – both upper and midsole. I tend to be a midfoot-to-forefoot striker and I think some of my form may contribute to that feeling. Walking in the Brooks Glycerin 21? Amazing. Heel striking? Great. But I kept wanting a bit more cushion under my forefoot to pay off the toe off.

Upper

Annie: Slipping into the Brooks Glycerin 21 had the same plush, silky feel I’ve come to expect from the brand’s more premium uppers. I’ve also yet to be truly let-down by a Brooks fit, and the last on which the Glycerin 21 is built is no exception. Length is spot-on, and I had plenty of wiggle room for my average-to-slightly-wide forefoot. A purposeful cinching of the lacing upon initial wear gave me all the lockdown I needed to lace up without further thought thereafter.

Drew, I know you’re also a fan of the typical Brooks fit and get along well with the accommodating volume in particular. Did the Brooks Glycerin 21’s upper keep the good times rolling?

Drew: Despite the updated looks, the Brooks Glycerin 21 fit was consistent with previous years. Extra room in the forefoot while narrowing a bit in the midfoot and heel without being overly constricting. Previous Glycerin fans will feel like they’re slipping on something familiar even though they’re getting several improvements.

The upper itself feels a little stretchier and comfortable too…which I didn’t even know was possible. But the move to this version of an engineered warp knit was a good one as it adds just a touch of comfort to an already luxurious upper.

Tyler: This upper is everything you want and more. Annie hit the nail on the head with saying she’s never been let down by the fit of their upper. Even the Stealth version from last year felt good, I just didn’t like the performance aspect of it. 

While not overly exaggerated, the wider forefoot added a notch of comfort to help toe splay. Bonus points to Brooks as even cinching down for a snug fit didn’t result in any bunching around the laces – which seems to be common in a lot of shoes with wider forefoots.

Traction

Annie: One thing that struck me about the outsole of the Brooks Glycerin 21 is the fact that the rubber is decoupled between the forefoot and heel (which was not the case on version 20). As I hinted above, I think this contributed to the natural, slightly snappier forefoot feel.

In the more experimental Aurora-BL, Brooks went so far as to decouple the entire midsole. And that was a step too far for me, due to my persistent princess-and-the-pea syndrome, which renders me averse to anything that feels remotely prominent under the arch of my foot (such as a midsole’s flex point being dictated to me). Decoupling only the outsole is the perfect compromise, and it provided the neutral, unobtrusive ride I prefer without making my foot too aware of how Brooks accomplished it.

Brooks uses its new “RoadTack rubber” compound in the Brooks Glycerin 21. The company describes it as, “a mix of rubber and recycled silica.” Now, to be fair, I’m not terribly hard on outsoles in the durability department. But for what it’s worth, I’m not sure you could tell I’ve run in the shoe at all based on how absurdly new the outsole still looks, even after logging nearly 50 miles.

As for traction, let me tell you, the weather I encountered during the testing period of this shoe was a straight-up mess. I had more inclement outings than dry ones, so the traction got thoroughly put through its paces in plenty of nasty road conditions.

I had zero issues in the rain, regardless of whether I was on debris-covered pavement, wooden pedestrian bridges, or even metal grates and the like. I trudged through snow and wintry mixes and had only the most minor, momentary slipping on the slickest of slushy surfaces. Do I think any road shoe is going to make you invincible when traversing ice? No, of course not (though some Puma models might come freakishly close…). But I can say that I was about as confident as I’d ever be frolicking about like a ninny (Editor’s Note: what the heck is a ninny?) and getting quizzical looks from neighbors as they plowed their driveways.

But let’s see how the outsole performed under Tyler’s and Drew’s demands.

Drew: I know this is boring but I had the exact same experience as Annie when it came to the traction of the Brooks Glycerin 21. Some slight slippage on ice and frosty boardwalks but rain, light mud, and the other inclement conditions I encountered weren’t a problem.

The four separate outsole pieces were appreciated as it resulted in the most flexible and natural Glycerin I’ve tested to date. I imagine this outsole construction costs more but I hope Brooks continues it as it made a noticeable difference.

Finally, despite the upgrade in rubber to RoadTack, the durability stays impressive. Last year Tyler and I hardly made a dent in the traction with 50ish miles each. The same held true for me this year. How about for you Tyler?

Tyler: I was more conservative in my testing and didn’t venture on any treacherous terrain like Annie or Drew, but found a similar – or even better – traction than last year’s model, hitting the road in some damper conditions. 

I’m sure the separations of the pods/outside pieces helped shave a little bit of weight (always a benefit), but while more dispersed across the foot, the outside pieces are placed in critical positions to avoid ground contact with the midsole, which I really appreciate. There is nothing worse than logging miles and seeing how wear patterns are only affecting the exposed midsole and not the outside – so good news, this is not the case on the Brooks Glycerin 21, even with a streamlined outside design.

Is the Brooks Glycerin 21 wide foot friendly?

Annie: Yep. The standard width of the Brooks Glycerin 21 was incredibly comfortable for my average-to-slightly-wide forefoot. And it’s also available in wide versions for anyone seeking some extra room.

Drew: For me, length was true to size and length/width was consistent with Glycerins of the past. The ample room in the forefoot means a lot of wide footers will get by going true to size in the standard width. As is typical for a Glycerin, the Brooks Glycerin 21’s two widths will allow even more people to enjoy this cruiser. 

Tyler: Absolutely. I would even argue that folks who teeter on needing a wide version should consider the regular fit. In addition to the extra space, the flexibility in the upper might offer a great fit without going wide.

Is the Brooks Glycerin 21 worth $160?

Annie: $160 is a common refrain in shoe prices these days, and it’s no small amount of money. I was a big fan of the Brooks Ghost Max last year (and still am), which was priced at an easier-to-swallow $150. However, I think the Glycerin 21, with its highly resilient DNA Loft v3 and more substantial outsole, is likely an even longer-lasting workhorse.

When it gets down to it, I always try to answer this question by asking myself if I’d feel like I got my money’s worth if I didn’t have the luxury of Brooks kindly sending us the Glycerin 21 and instead had forked over my own $160 in order to run in it. And the truth is, I’d feel pretty good about my purchase in this case.

That said, there’s always the consideration of last year’s model when it comes to getting a solid shoe for a lower price. In fact, up until this running reviewer gig kept me in current models, the only way I was able to get my hands on the shoes in my personal rotation was by doggedly seeking out price reductions of some kind or another.

So, Tyler and Drew, you extensively tested out the Glycerin 20 last year. What do you think? Should people bide their time on the Brooks Glycerin 21 for now and instead get the previous version for a great deal? Or does this update put its performance where its price tag is?

Drew: I’d say most people will be able to utilize those Glycerin 20 discounts until they can’t find their size anymore. The Brooks Glycerin 21 is just slightly better in most ways but if you’re saving $40-50 you can wait for those slight improvements.

The only people I’d recommend go ahead and get the Glycerin 21 ahead of the Glycerin 20 are bigger runners (like me…and Tyler). The extra 2mm of cushion is helpful at our size when banging out miles on concrete during marathon training. Do you agree Tyler?

Tyler: Eh, I want to recommend the shoe because it’s so close to being the perfect companion that you can turn to for a lot of runs, but the lack of forefoot cushioning is stopping me from doing that. If I’m going to bang out some recovery runs, I want a shoe that doesn’t nag and I found this one nagging here and there. I’d agree with Drew that the 20 might be the Glycerin I would recommend as I found that ride a bit more evenly cushioned. 

In full transparency, I was A/B testing this shoe against the Nike Vomero 17 (same price point) and felt that it provided a more cushioned and well-rounded ride that I preferred.

Brooks Glycerin 21 Summary

Annie: The Brooks Glycerin 21 has the fit and available sizing (and even stability options, for that matter) that make it readily approachable for a broad range of runners. It may not be the flashiest or most dynamic of shoes out there, but it sports a midsole foam that provides “distraction-free” protection that will last a high volume of smile-inducing daily and long distance (s)miles. 

And if the Brooks Ghost Max, Hyperion Max, and Glycerin 21 are early indicators of what else Brooks might have up its sleeve, I think the brand could be in for a particularly auspicious 2024.

Drew: Unlike Annie, I’ve seen what Brooks has up its sleeve for 2024 and it’s looking like Brooks’ best year ever since I’ve been reviewing running shoes. What I didn’t expect is for the Brooks Glycerin 21 to be a clear upgrade from a very good Glycerin 20 and immediately grab a place in my post testing rotation. 

If you’re not ready to pull the trigger and purchase it, be careful trying the Brooks Glycerin 21 on in store. It’s got the kind of all around comfort that makes you want to wear it out the door. 

Tyler: The Brooks Glycerin 21 is my sweet spot when it comes to a shoe and on paper, is everything I like. But I just can’t get over the desire for a bit more forefoot cushioning to fully endorse it. While I haven’t tried the Brooks Ghost Max, it’s on my list and I’m hopeful I might find something a bit more enjoyable in it. And, knowing Drew’s affinity for Brooks, I’m sure we’ll see (and try) some other models in 2024 that exceed expectations.

Disclosure

While Brooks did send pairs of the Brooks Glycerin 21 to facilitate this review, they had no involvement in this review, didn’t receive an advance look at it, and have not attempted to influence it.