For several years now, Nike has set the standard for elite road running shoes. The Vaporfly and the Alphafly are the brand’s premium racing models. They showcase cutting-edge designs and materials, including carbon fiber midsole plates and ultralight, ultra-bouncy cushioning foams. The tech works: When Eliud Kipchoge set a new world record for the fastest marathon last year, he wore a pair of Alphaflys on his feet. With its speedy reputation firmly established in the world of road running, the Swoosh is now turning its attention to the dirt. Earlier this year, the brand unveiled the Ultrafly, a carbon-plated trail shoe designed for racing — and winning — on the trail.
Design and Materials
Nike calls the Ultrafly its “flagship racing shoe” for trail running, and it’s packed with the brand’s latest running shoe technology. The midsole is made from ZoomX foam, the same stuffed used in the Alphafly and Vaporfly racers (as well as several other Nike models). This foam is made from polyether block amide (PEBA), a lightweight, exceptionally responsive material that provides good shock absorption and a springy ride. The foam is paired with an embedded carbon fiber plate, another common feature among pavement-oriented racing shoes. With each step, the stiff plate bends when you land and then snaps back into shape, creating an extra boost of energy return at toe-off.
The Ultrafly outsole is also a highlight. The shoe features a Vibram Litebase outsole, a new rubber tread design that’s 30 percent lighter and 50 percent thinner than typical outsoles, according to Vibram. This makes the Ultrafly lighter while still giving it a strong grip and durability for off-pavement running. The shoe is topped with a Vaporweave upper with an integrated heel counter for a sturdy and supportive feel around the back of the foot.
Testing
I tested the Ultrafly over the course of two weeks on several routes at a state park near where I live. The park has miles of trails to explore, all involving significant uphill and downhill treks on hard-packed dirt with some areas of loose gravel. Many of my test runs included stretches of pavement — although the Ultrafly is not designed for road running, it felt comfortable on the asphalt, too (more on that below).
What We Like
- Secure, Comfortable Fit: Many Nike shoes have a narrow fit, especially at midfoot — I’ve tried several pairs that constricted my feet. Thankfully, that’s not an issue with the Ultrafly. The shoe has a notably wide toe box, and it gave my toes plenty of room to spread out while running. The midfoot isn’t quite as generous, but it never pinched my feet, and the Vaporweave upper created a snug wrap around the middle and top of my feet. Within the upper, an integrated strap runs from the footbed to the lacing eyelets at the midfoot; this feature helped the upper conform to the shape of my foot and keep it in place on the footbed.
- Smooth and Stable Ride: With its close fit, wide forefoot and relatively flat outsole, the Ultrafly served up a smooth ride and displayed excellent stability in my testing. The shoe felt planted and controlled on uneven ground and when negotiating switchbacks on hilly trails. A few key features contribute to this poised feel. First, the Ultrafly has a rocker sole shape (where the sole turns upward at the toe and heel), which encourages gentle transitions from landing to toe-off. In addition, the wide sole shape and stiff carbon fiber plate in the midsole gave my feet a supportive landing platform and kept them from rolling sideways during my stride. The carbon fiber plate also created some protection: It prevented exposed rocks from poking up through the sole and bothering my feet. Overall, the Ultrafly felt smooth and easy on my feet — great for zoning out and racking up lots of miles.
- Good Grip: The Ultrafly excelled on hard-packed trails, providing reliable traction on both uphills and downhills, and it handled patches of loose gravel and rock stairs without a slip. Although it’s not marketed as a road-trail hybrid, the shoe also felt great on the pavement: The rocker sole and shallow outsole lugs (the cleat-like protrusions at the bottom of the shoe) gave it a comfortable ride on city sidewalks. I often wore the Ultrafly on routes that took me from my apartment through the state park trails and back. It seemed ideally suited to this kind of mixed-terrain running.
What We Don’t
- Break-in Time: The Ultrafly is a well-cushioned shoe, but it takes some time for that cushioning to wake up. The Ultrafly has a taller stack height (i.e. more midsole foam) than the Nike Wildhorse, my favorite trail shoe, but the key difference is in the midsole material. The Wildhorse uses React cushioning foam and the Ultrafly uses ZoomX foam. In my experience, shoes with React midsoles feel soft and bouncy right out of the box, while shoes with ZoomX feel firm at first — the foam needs to break in a bit. After a few runs, my test pair started to soften up, and the shoes felt more cushioned and bouncier as a result.
- Breathability: The Ultrafly’s Vaporweave upper prioritizes durability over breathability. The material doesn’t have any large open pores where heat and sweat vapor can escape, and in my test runs, my feet felt hot and sweaty. It wasn’t enough to derail my run or cause serious discomfort, and wearing thinner socks might’ve alleviated the issue. Even so, it’s something to keep in mind, especially if your feet tend to overheat while running.
- Shallow Outsole Lugs: The outsole has notably shallow lugs — about 3.5mm, according to Nike’s official measurement. Most trail shoes have lugs that measure around 5mm, and some trail shoes have lugs even toothier than that. While I never encountered any issues with traction during my testing, the shallow lugs aren’t well-suited to mucky or highly technical terrain: They won’t dig into soft ground as well as bigger lugs do. If you frequently run in these conditions, you might want to consider a different shoe.
Should You Buy It?
With its stable, responsive feel, comfortable ride and grippy outsole, the Ultrafly is a strong choice for trail runners who are focused on distance. At about 10.6 ounces for a men’s size 10, it’s not an ultralight model, so it’s best for longer efforts when you need a cushioned shoe to keep your feet comfortable. In addition, those shallow outsole lugs will be overmatched on loose terrain or paths with lots of rocks and roots (familiar hazards for East Coast trail runners). But if you’re lining up for an ultramarathon on buffed-out trails, the Ultrafly is the shoe you want on your feet.
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