Brooks Glycerin 21 Introduction

Super soft cushioning for supreme comfort”, that’s the product description of the Glycerin 21 on the official Brooks website.

My very first Glycerin was the 16th version, many years ago. It wasn’t a super soft trainer back then and now, 5 versions later, neither is the Glycerin 21. I agree with brooks that it is supremely comfortable though. The Glycerins are some of the most comfortable trainers I’ve ever worn.

The Glycerin is Brooks’ max-cushioned trainer and while it is the softest Brooks trainer, compared to other max-cushioned trainers from other brands, like the Invincible Run, the More and the Nimbus, the Glycerin has a much firmer ride. This makes it a sturdy, stable shoe suitable for heavier runners.

Last year’s Glycerin 20 was one of the biggest Glycerin updates because it switched from a regular EVA midsole to a supercritical, Nitrogen infused midsole. This made the ride softer when walking but firmer when running because the new-age foam decompressed much faster after each foot strike.

This year’s version retains its DNA Loft v3 midsole but it has a different geometry. It also has a new upper and outsole.

The Glycerin 21 weighs 278 g (9.8 oz) which is 8 g (0.3 oz) less than the Glycerin 20- impressive considering the 21 has 2 mm extra stack height in the heel and forefoot. It still has a 10 mm drop and costs $160.

Brooks Glycerin 21 First Impressions

My first run was the second run of the day, a very slow 8 km recovery run on tired legs. During the first 3 kilometres, I could feel the raised side walls in the forefoot and midfoot which was annoying.

This was surprising because this is the regular Glycerin and not the GTS version. Luckily this sensation disappeared after the first 3 kilometres.

The shoe provided plenty of protection and my legs felt really happy during that run. The ride didn’t feel super soft but it felt very balanced- more like a daily trainer than a max-cushioned trainer. The upper fit me like a glove and it was really comfortable and conforming.

It reminded me a little bit of the Aurora-BL, also from Brooks but the Glycerin 21 didn’t feel as soft, energetic or unique. The Aurora was the first trainer to feature DNA Loft v3.

Brooks Glycerin 21 Upper

The upper of the Glycerin 21 is luxuriously padded with smooth lining on the inside, a textbook max-cushioned upper. I have no issues with hot spots or heel slippage but I do find it extremely warm.

It has a new knitted upper which is softer to the touch but has lower breathability. It stretches more and conforms to your feet better than the traditional mesh upper of the Glycerin 20 and it’s noticeably thicker.

The padded tongue is not gusseted but there isn’t excessive tongue slide because there is a loop on the tongue for the laces to go through. The laces have been changed to soft, thin oval laces which fray easily. I prefer the flat laces on the previous version because they feel more premium.

The Glycerin 21 has a narrow fit but it’s also available in a wide version. I find it true to size but a little bit shorter than the average running shoe. Its toe box is wider than the Glycerin 20.

Brooks Glycerin 21 Sole Unit

The biggest and most notable update to the sole unit is that the Glycerin 21 has lateral side rails in the forefoot and midfoot to help keep your feet centred, similar to the Glycerin GTS version. This is designed to increase stability, but I didn’t notice a big difference.

I’m a heel striker so perhaps it works better for forefoot or midfoot strikers. I don’t think the Glycerin 21 needs the side rails because the GTS version has these for runners needing extra stability and the regular version was already a very stable neutral shoe without them.

The Glycerin is the same type of max cushioned trainer as the Hoka Bondi. They both have firm but cushioned rides which suit runners who want a stable platform without much squish.

The Glycerin 21 is a brilliant long run shoe because it has deep cushioning and it’s easy on the ankles due to its midsole which isn’t overly soft. I did a 35 kilometre long, slow run in it and I really enjoyed how comfortable and sturdy it felt. Version 21 is slightly wider than version 20 to account for the increase in stack height so it’s even more stable.

Although the Glycerin 21 has thousands of tiny nitrogen bubbles in its DNA Loft v3 midsole which make it supercritical, it doesn’t feel as bouncy as you’d expect. It feels very padded and absorbs shock well but it doesn’t make me want to run fast. Only slow, relaxed runs are in the Glycerin 21’s wheelhouse. My easy and recovery runs are what I use it for.

There’s a lack of a prominent forefoot rocker in the Glycerin 21 so it feels flat compared to the new Brooks Ghost Max which has faster transitions and a stiffer forefoot. Version 21 is also more flexible than version 20 so it feels less snappy.

The outsole design is quite different to its predecessor and the Glycerin 21 has less rubber on the midfoot which saves some weight. The 21 outsole is more segmented in the forefoot which makes it more flexible. The rubber lugs are thick and hard-wearing so you won’t have any durability issues.

The exposed midsole foam is also really tough and won’t show many scuffs or abrasions. After 80 kilometres in my pair, it’s barely showing any outsole wear.

I wore the Glycerin 21 in the rain numerous times and I didn’t slip but traction is average on wet surfaces- the rubber lugs are not very aggressive.

Brooks Glycerin 21 Conclusions

The Glycerin 21 still doesn’t have that super soft cushioning that Brooks advertises, but that’s not a deal breaker. Not everyone wants a soft max-cushioned trainer.

The Hoka Bondi is an example of a firm max-cushioned trainer that sells by the boatload. It was the 2nd best selling running shoe at Running Warehouse this year and last.

I personally prefer my max-cushioned trainers to be lighter and more bouncy but I’m a light runner (60 kilograms) so I don’t think I’m benefiting from the Glycerin’s tank-like build.

The Glycerin 21 stands out from the crowd of max-cushioned trainers because it can withstand a beating. It has a thick, hard-wearing outsole and a midsole foam which doesn’t compress much over time.

Version 21 is an improvement over version 20 because it provides a softer, plusher ride due to the increase in stack height and it has a more comfortable upper with a wider toe box.

I think the Glycerin could be improved by having an even taller midsole and a more prominent rocker to ease transitions. Hopefully the Glycerin Max will have these features when it eventually comes out.