Brooks Glycerin GTS 21 Introduction

The Glycerin GTS 21 follows the Glycerin GTS 20 and continues to offer a stable ride with a very smooth transition. Glycerin GTS is the stability version of Brooks’ Glycerin, which means it is the same shoe but with the added feature of GuideRails® to help guide the foot through regular pronation.

Glycerin GTS is the most plush stability offering from Brooks, joining the Launch GTS with its speed focus and Adrenaline GTS which sits between the two in cushion.

This shoe retails at $160 USD, the same as last year and as the Transcend 4, 5, 6 and 7, the previous name for Brooks’ most plush stability shoe (the cost was $10 lower for the first year when the name and design switched to “Glycerin GTS 19”).

The listed weight remains at 10.5 oz. (297.7 g.) in a US M9 and drops slightly to 9.2 oz. (260.8 g.) in a US W7; the StealthFit version with a compression knit upper is about a half ounce lighter.

Brooks allows runners to choose their preferences with choices for “StealthFit” or “Classic” for the upper and “Neutral” (Glycerin) or “Support” (Glycering GTS) for the midsole, regular or wide width.

Glycerin GTS competes with Saucony Omni, New Balance Vongo, and ASICS Gel-Kayano for top-end stability offerings.

Overall, I recommend Glycerin 21 GTS over the Saucony Omni 22 with two exceptions:

1) I take the sock liner out of Omni to put in Glycerin; it’s thicker and offers more arch support;

2) You’ll probably prefer Omni if you have a narrow foot. I stayed with the half-size smaller in Omni than Glycerin because though I’d prefer a slightly wider toe, the length was true to size. Sizing up would have made it really long.

Choose Vongo if you want the extra stiffness and spring of a nylon-plated shoe and Glycerin GTS if your foot gets uncomfortable wearing a plated shoe.

Brooks Glycerin GTS 21 First Impressions

Unboxing Glycerin GTS 21, I loved the slick, clean style and looked forward to stepping onto this plush, attractive model.

It did not disappoint in feel underfoot, but I knew right away that I would need to size up a half size. True to the .2 oz drop in the listed weights (for women), the 21 in my size 10 weighed the same as last year’s size 9.5.

The first run felt smooth, and this continued through my testing period (70 miles).

Brooks Glycerin GTS 21 Upper

A higher, more solid heel counter this model is a nice surprise; padding around the ankle is moderate. My heel did not slip, and my foot felt supported.

The shoe has better breathability and a more comfortable fit that does not require as long of a break in as in the 20.

The StealthFit upper option, available in both Glycerin and Glycerin GTS, allows for even more stretch, like Nike’s Flyknit in their React Infinity Run FK 2.

My least favorite part of the shoe is the sock liner. It is average, but for a $160 shoe I would hope for something more robust and supportive under the arch, like I found in the ($30 less expensive) Omni 13. After about 40 miles of testing the Glycerin GTS sock liner felt flat. I like to put the Omni liner into the Glycerin GTS for a better feel underfoot inside the shoe.

The look is attractive and inviting, with a less-busy pattern than the 20 and a variety of colorways to choose from.

Brooks Glycerin GTS 21 Sole Unit

This nitrogen approach brings a unique feel: soft yet resilient — not plush, but comfortable. The ride is light and airy, with a rocker feel underfoot and quick transition into toe-off. The drop is 10 mm.

The GuideRails® remain largely unchanged since their 2019 revamp in Transcend 6. This unique approach to counter excess motion and alleviate pressure on knees and hips works together with the upper’s heel counter to rein in movement.

The GuideRails® consist of the midsole extending up to border the shoe to provide support if needed. If not, they are not noticeable. The GuideRails® also help support the arch of the shoe to direct foot motion forward rather than rotating too far inward.

Again this year the thin, carbon-rubber outsole will be the first part of the shoe to evidence wear. An additional flex groove just before toe-off exposes the midsole, and after 70 miles on my shoes I can already see it starting to fray.

On the positive side, the outsole covers more of the lateral midfoot.

Brooks Glycerin GTS 21 Conclusions

This is a remarkable shoe that is fun to run in. The main thing keeping me from giving it five stars is the “meh” sock liner.

Sock liner aside, try Glycerin GTS 21 for the best in cushion, stability, and upper support.

Before buying, first check to see if you have heavy wear patterns under the medial toe box on your previous shoes.

The new flex groove under Glycerin GTS’s big toe exposes the midsole, and it might be a warning for you to try a different model to avoid premature wear.