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Finlay McAndrew  •  Running Gear •  01.02.2024 •  6 min read

Brooks Glycerin 21 Franchise Running Shoes Review

The Brooks Glycerin 21 franchise has been updated to offer even more cushioning and a new upper design. This article explores the key changes, how they feel to run in, and how to pick between the Glycerin and Glycerin GTS. 

Men's Broooks Glycerin 21 running shoe in Blue colourway sitting on bench

What’s changed?

The main change is more cushioning in the midsole. To explain further, there’s now an additional 2 mm of Brooks’ nitrogen-infused DNA LOFT v3 foam. Taking the stack height to 28 mm in the heel, and 18 mm in for the forefoot. 

There’s also changes to the outsole design. As this is now made with a new RoadTack rubber which includes recycled silica. Overall, the shoes are made with recycled materials equivalent to 5 plastic water bottles.

Finally, an updated upper should offer an improved fit. The engineered warp knit design should feel breathable, flexible and soft against your feet. 

What’s the difference between the Glycerin 21 and Glycerin GTS 21?

There’s one specific difference between the standard Glycerin and GTS version: the GTS version features Brooks’ GuideRails holistic support system. If you’re wondering, GTS means ‘Go To Support’. That doesn’t mean the standard Glycerin don’t offer support, as they do. It’s just that the GTS edition offers a enhanced structure that has the potential to support your feet and legs to a greater extent. 

Brooks’ innovative GuideRail technology helps support your body in its natural motion path, while keeping excess motion in check. How does it work? There’s two rails on either side of the midsole (rising up at either side). The section on the medial side is firmer than the density of the midsole. This provides some added support if your feet have a tendency to pronate excessively. The unique attribute of the GuideRail support is that it has the potential to actively minimise internal knee rotation. Greater ranges of internal knee rotation are often the route of pain and irritation in that area. 

Runner standing in Brooks running shoes with right leg raised and tilting inward

For the avoidance of doubt, there’s no difference between the cushioning and protection on offer between the Glycerin and Glycerin GTS. The choice simply comes down to what level of support you need for your feet and legs. As mentioned above, the Glycerin 21 still offer support for your feet and legs throughout the gait cycle. The wide base and soft and protective cushioning all work together to reduce the stress on working muscles.

We suggest choosing the GTS version if you’re prone to knee discomfort, or if you’ve been previously fitted with stability running shoes. If not, the standard Glycerin are likely to be the better option. 

How does the Brooks Glycerin 21 cushioning feel to run?

Brooks kindly sent us a pair of Glycerin 21 to test out so we could review them properly. The DNA LOFT v3 cushioning feels very protective and cushioned, but not ultra soft. This is in comparison to some of the very soft and spongy running shoes available in the market right now. As a result, the cushioning feels very stable, in addition to offering a lot of underfoot comfort. Many runners are looking for cushioning alongside great support, and that’s what the Glycerin 21 offers.

Sequence image showing male runner running in blue Brooks Glycerin 21 running shoes on a sunny day

In terms of pace, they’re likely to feel best on slower paced runs. Yes, you can definitely use them for steadier paced runs, but you might just find they lack a bit of responsiveness for this type of effort. The main reason they feel so good for easier paced runs is that the cushioning feels incredibly comfortable. As a result, you can just forget about your feet. This also means they’re great options for longer distances. 

The outsole grip performs well in wet conditions and offers a lot of traction. The high degree of outsole rubber should also offer great levels of durability. Yes, there’s a slight weight cost to this. However, weight is not such an important factor when you’re running at easier efforts. Durability is far more important.

Pair of blue Brooks Glycerin 21 running shoes propped against a wall. One shoe flipped over to reveal the outsole.

How do they fit?

The upper feels very accommodating and spacious in the toe box. As a result, they should fit well for runners with broader feet. However, I should note the upper definitely felt a little bit tighter on the first couple of runs - so they do loosen off a bit. Don’t be put off if they feel slightly snugger than you expect when you first try them. 

The warp knit fabric is very soft, light, and supportive. I’m not sure exactly how it’s achieved, but the midfoot area feels really supportive and offers great lockdown. This is a real stand out feature, as many runners are looking for this sensation.

None of the Glycerin’s trademark plushness in the upper has been lost. The padded tongue is great at reducing lace pressure, and feels very comfortable. Additionally, the padded heel collar delivers a soft, yet secure and supportive fit. It’s a great design for runners who are prone to rubbing or friction around the ankle area. 

Close up of upper/ankle area on pair of Men's Brooks Glycerin 21 running shoes in Blue/Nightlife/Black colourway

How can the Brooks Glycerin 21 improve your run?

The Brooks Glycerin delivers exactly what they should: great comfort, support, and lots of protection. These are the attributes that you should be looking for in your running shoes for easy miles and aerobic effort runs. 

It’s worth pointing out that there’s a lot of choice in this area. In our opinion, if you’re searching for the softest underfoot experience, the Glycerin are not necessarily going to deliver that. However, cushioning can be a subjective matter. Additionally, the softest shoes don’t necessarily always offer the most cushioning. Runners sometimes find ultra soft shoes are slightly unstable on their feet too. This is where the Glycerin franchise excels. They strike a great balance between softness and responsiveness. Ultimately delivering amazing cushioning that feels very stable to run in. If this is what you’re looking for in your running shoes, it’s likely the Glycerin franchise are going to suit you.

Finally, it’s worth highlighting that the Glycerin models should help you on days when you’re feeling tired. Whether that’s because you’ve had a long day at work, or you’ve done a tough interval workout the day before. This could help improve the consistency of your training. Particularly if you’re trying to run on consecutive days.

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