Brooks Glycerin 21 Review: Deep, Soft and Smooth

Always a favourite of many runners' rotations, the Glycerin series has had a long run and for a good reason. Does the newest iteration carry the mantle well?

Brooks Glycerin 21: Evolution of the Series

The Glycerin 21 is the latest version of Brooks’ daily workhorse. The Glycerin 20 was very popular with our testers. Tim said that it was one of his shoes of the year because it was so easy to just put on and run daily mileage. So how does the 21 differ and is it worth the upgrade?


Let’s dive into the details and find out!

June Monthly Round Up (8 of 12)
Brooks Glycerin 21 (9 of 12)


Weight in Brooks’ sample size: 271g/9.6oz


Stack height: 36mm in the heel with 10mm drop to 26mm in the forefoot


MSRP: €180/$160

Brooks Glycerin 21 Upper: Comfortable, Simple and Plush

Brooks is renowned for their uppers and fit. Endless comfort and a shape which suits most feet make them some of the best selling shoes in the world. Brooks offer the Glycerin 21 in both classic and StealthFit configurations. For the purposes of this review, I was running in the classic version. Here, there are minor changes to the Glycerin 20.


Firstly, there is a lot of upper. The Glycerin is designed for comfort through whichever distance you run and it starts here. At the rear of the shoe, the heel collar has a good amount of padding and is low-rise in comparison to many of its competitors. Along with the padding, it is also a very stout heel counter. Once your foot is in the Glycerin 21, it isn’t sliding out. Moving forward, the tongue is non gusseted and very thick. Even when cranking down the laces, the tongue ensured that there was no pressure on the top of my foot. Furthermore, it always stayed in place during the run. Continuing the plush comfort theme, the warp knit upper wraps the foot well and means that lockdown is very easy to achieve. 


Overall, the upper does exactly what you want in a daily shoe. It holds the foot tight, it is comfortable and takes no fussing to sort before you head out of the door. On the negative side, I am not sure how the upper will perform in the summer months when the temperature soars. During winter running when the scale has dropped into the negatives and rarely reached double figures, my foot has been pleasantly warm. This leads me to wonder whether that pleasant warmth will turn into a swampy sweat when the sun starts shining.


Finally, whilst the laces are fairly standard affairs which do the job. I found them to be very long! In fact, I am pretty sure that I could cut mine in half and still have enough to lace them well. That being said, it does mean that tying a runner’s knot or other lacing configurations should be no issue at all.

Brooks Glycerin 21 (2 of 12)
Brooks Glycerin 21 (5 of 12)

Midsole: More DNA Loft v3 Than Anywhere Else

What do you want from a daily shoe? Reliable, cushioned comfort? A springy, bouncy and energetic ride? 


If the answer is the first one, the Glycerin 21 may very well be the shoe for you. Here, Brooks’ DNA Loft v3 foam takes centre stage. With 2mm more than in the 20, it is the thickest slab available in any Brooks shoe. The Ghost Max doesn’t have v3. During the run, the midsole provides plenty of shock absorption and easy comfort. I have used the Glycerin 21 on runs to distances up to ~20km and found them to be comfortable for every step. The midsole isn’t an overly proscriptive design which tries to make you run in a certain way. As a high cadence, very forefoot (tippy-toe even, thanks Instagram!) runner, I have found it helps me bounce along while leaving my legs fresh afterwards. 


On the other hand, DNA Loft v3 doesn’t offer a huge amount in energy return. Whilst I have taken the Glycerin 21 to around my marathon pace, I probably won’t be lacing it up if I am chasing a PB. However, that isn’t really the purpose of the shoe. This is for the miles which get you to the start line rather than the glory miles of the race itself. 


As with the upper, there is a lot of midsole, both in depth and width. Stability is not really an issue in the Glycerin 21. Although, if that is your primary concern, the GTS version offers increased stability with Brooks’ GuideRails technology. For the majority of the daily miles the Glycerin 21 is a simple shoe to pick. Smooth transitions through the gait cycle, soft but not mushy cushioning mean that is a good addition to just about any rotation.

Brooks Glycerin 21 (11 of 12)
Brooks Glycerin 21 (3 of 12)

Brooks Glycerin 21 Outsole: RoadTack to the Resuce?

Underfoot, the grip duties are handed to the new RoadTack compound. Whilst not full coverage, the rubber is strategically placed in high wear areas. Gaps and flex grooves mean that the outsole doesn’t add too much uncomfortable rigidity. Every section of rubber is at least a couple of mm thick which will give it good durability.


The majority of my runs have been during a very wet winter. This means that I have had plenty of chance to see how the RoadTack rubber performs in inclement conditions. For the majority of time, there is no issue with the grip or performance. Through puddle riven roads, soggy leaf mulch and slick paving slabs, it has held me firm. The rubber is also showing no signs of wear after my initial 60km in them.


The only time where the outsole has given me questions have been the odd occasion when I have had to take a detour over muddy, wet grass. Here, they have not been very impressive. Although I can usually avoid this on my routes, it does limit the versatility of the Glycerin 21. If your running route involves trail sections or grassy areas, this may be worth keeping in mind.

Brooks Glycerin 21 (12 of 12)

Conclusion: Plushness at a Price

Is the Brooks Glycerin 21 a dependable daily trainer? Absolutely. It will help you through many a mile with the mid and outsole compounds bound to deliver good durability. Whilst it may not be the most exciting shoe on the market, that isn’t always what is needed when working through the miles to your next marathon. 


The only issue I would have is with the price. At €180/$160, this opens the Glycerin 21 to a lot of competitors. For a similar ride but a lot less money out of the pocket, it is worth considering the PUMA Velocity NITRO 3. If something with a little more pep and pop is your preference, there is the now more daily based New Balance Rebel v4. For a similar price and a lot more cushion, there is the Saucony Triumph RFG.


That being said, if something dependable, durable and fuss free is your bag, the Glycerin 21 will be a very good choice for a wide range of runners.

Brooks Glycerin 21 (6 of 12)


45 years old

173cm (5’8″) – 66kg (145lbs)

Forefoot striker – (Very) high cadence runner


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