Float on Your Long Runs in the Asics Gel-Nimbus 21

The Asics cushioned trainer gets a few updates for its 21st birthday.

Weight: 314g (M), 263 (W)
Road shoe
Best for: 
Long training weeks on unforgiving footpath


The Nimbus is now old enough to order a drink. A longtime favourite for its soft cushioning and long-distance durability, the Nimbus doesn’t undergo much of a “new year, new you” overhaul with its 21st iteration but maintains the elements that have made it such a perennial go-to. For starters, it has an ultra-smooth and supportive ride. Add to that praise our appreciation for the shoe’s triple layer of responsive cushioning and no signs of wear after the first 50 miles, thanks to a high-abrasion rubber outsole.

There are only a few minor complaints we had with the shoe. Some of our testers found it a bit on the heavy side—though at 263 grams for the women’s version (314 for men’s), the 21 is well within the “normal” range on a BMI chart of distance shoes. Personally, I found the weight to be fine but the upper to be too structured and narrow for my forefoot. Runners who prefer more wiggle room in the toebox might want to give this shoe a wide-footed berth—though Asics claims this year’s iteration has an improved fit and more toe space than ever before. (I guess I’ll check back in with the 22.) That said, there’s plenty to love about this high-mileage trainer. Let’s start with the veritable foam party in the midsole.

A Trifecta of Cushioning

The Gel-Nimbus 21 has plenty of padding, with three different kinds of midsole cushioning packed in like the layers on a multi-tiered cake. At the top, the Nimbus has what Asics calls “Flytefoam Propel,” a lower-density foam designed to create continuous cushioning. Beneath that, Asics adds “Flytefoam Lyte,” with an elastomer for higher energy return and faster toe-off. And at the heel and forefoot, Asics injects its ubiquitous impact-reducing Gel technology, which is now less visible from the outside of the shoe. The combined effect is a ride that’s soft but not to the extreme—with enough responsiveness that your foot doesn’t feel like it’s being sucked down into a pillow. For long runs, the midsole can stand up to many miles of harsh pavement without losing its rebound or battering your legs.

Boosting comfort is an Ortholite sock liner, designed for “excellent moisture management and a high-level of breathability.” Translation: it resists stink better and offers a softer underfoot sensation than the flimsy white foam models you often find in shoes.

A Sole Built for Distance and Stability

Underneath all that foam is a full-ground contact outsole, with high-abrasion rubber delivering good traction on both wet roads and trails. I’ve always found Asics to be highly durable in this regard, with an effective rubber placement and thick patches that endure hundreds of miles without signs of wear.

Although the shoe is designed for neutral runners, it has a few stability features throughout, such as a one-sided plastic “trusstic” on the sole that’s intended to add some support and gait efficiency. I found the shoe overall to feel a bit too structured and not as flexible as my usual trainers. Compared to the previous year’s Nimbus, our lab testing shows that the 21 has sacrificed some flexibility, though stability remains on par. And while we’re looking under the hood of the shoe, it bears mentioning the Nimbus is spec’d to have a 10mm heel-toe drop, but we found the men’s to be slightly flatter and the women’s to have a taller heel.


A Streamlined Upper and No-Slip Heel

The Nimbus 21’s upper is built with a new two-layer jacquard mesh design. After a week of warm-weather runs, my feet had no issues with overheating or breathing inside the mesh upper—though they did feel squeezed a bit right at their widest point. As mentioned previously, this might not be the best shoe for wide-footed runners due to a limit on in-shoe real estate at the forefoot. However, testers with narrower feet found the shoe to be comfortable throughout.

As for the rear of the 21, the well-padded collar was soft and cozy around my ankle. An exoskeletal heel counter initially appeared overbuilt but actually held my foot in place quite well without being intrusive or seeming to add too much weight to the heel.

Test Impressions

Six weeks out from the Austin Marathon probably isn’t the best time to bust out a new pair of running shoes. But I’ll admit I’ve never been that great at sticking to race-training best practicesPlus, this was just a cutback week—after back-to-back weeks with 32-kilometre long runs, I had only to get through 14 miles, a comparative skip around the block. That new-shoe glow alone could probably float me through the first seven or so, right?

Well, not so much. From the moment, I laced up, I knew I might have a problem with these shoes. My feet, which are fairly wide in the forefoot, started to feel stiff and cramped at around mile 8, which made the next six miles a bit of a slog.

As I stopped to remove the shoe from my apelike foot and stretch, I had some time to think about what worked well for me here. The cushioning was soft and efficient at the heel and forefoot without feeling like it sucked up all my rebound. The ride was smooth from landing to toe-off. The rubber outsole gripped the road just enough without adding excess friction or making me a fall risk. Any added weight was mostly unnoticeable—and I actually liked the sturdy feeling of this slightly heavier shoe underfoot for long mileage. I converted the run to a 12-miler, loped home, and confirmed these test impressions over a week of (shorter) runs.

To be fair, another wear tester described the shoe’s comfort level as “like a glove,” and others shared my impressions of the shoe’s ride.

We put each shoe through real-world usage and a battery of mechanical tests in our lab to provide you with objective—and exclusive—data. In addition to a shoe’s weight, we measure sole thickness (everything that sits between your foot and the road), how well the foam cushions your stride, and the flexibility of the forefoot. All this is taken into account in our reviews of each shoe.


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