Nike ACG Ultrafly Trail Review

The Nike ACG Ultrafly Trail is a great option for fast and flowy trail running. All photos: iRunFar/Bryon Powell

I distinctly remember when the original Nike Ultrafly, the predecessor to the Nike ACG Ultrafly Trail ($260), started appearing on the trails. How could I forget? It was at Western States in 2023, which I was lucky enough to run. While I was preoccupied with my race, the Nike Ultrafly (review) was creating a stir at the front of the field — and among my crew, who got seeded this new trail super shoe while they awaited my arrival at Foresthill. Several weeks later, I got my hands on my own pair and quickly accumulated 250 miles on them. In short, I was obsessed!

Since those Ultraflys were a stand out among my favorite running shoes, I was excited to test the second iteration with a slight name change, the ACG Ultrafly Trail, during late spring 2026. Although I managed to put more than 200 miles on them while getting in shape for summer mountain running, I wasn’t so sure about this shoe during my first few runs — they fit my foot differently and felt stiffer than the original. However, as the miles stacked up, they’ve really grown on me.

The Nike ACG Ultrafly is a trail running super shoe, which means it combines lightweight, responsive foam and a carbon plate and is designed specifically for racing. The shoe has an actual weight of 9.4 ounces (267 grams) for a U.S. men’s 9. It has 37 millimeters of stack height under the heel and 28.5 millimeters under the forefoot, for an 8.5-millimeter heel-to-toe drop.

The Nike ACG Ultrafly Trail is included in our Best Nike Running Shoes guide as the brand’s best trail racing shoe.

Nike ACG Ultrafly Trail Upper

A lateral view of the Nike ACG Ultrafly Trail.

Among the changes to the newest Nike ACG Ultrafly Trail is a redesign of the shoe’s upper. It was adjusted to provide more room in the toebox while maintaining a secure fit with an internal foot wrap. The lightly padded tongue protects and cushions the top of the foot, feeling comfortable even when the laces are cinched down tight. The rest of the upper is a thin, lightweight material that’s designed to drain water and dry quickly.

Indeed, this Ultrafly feels roomier in the toebox and more accommodating to a higher volume foot than its predecessor, providing slightly more space for toes to move and splay. At the same time, the glove-like fit around the midfoot and snug cradle for the heel kept my foot locked down, and I never experienced any hot spots.

The upper also drains well, thanks to a thin-but-sturdy upper material and small perforated drain holes near the front. After splashing through creeks and mud during the spring thaw in the Oregon Cascades and California Sierra Nevada, I was pleased with how quickly these shoes stopped squishing and felt dry again.

With more than 200 trail miles on these shoes, which included treading over volcanic lava rock and coarse granite, the upper remains in good condition. There is one notable wear spot around the inside heel collar of the right shoe — however, this is a common wear spot in all of my shoes and I don’t think it signals any durability concerns specific to the ACG Ultrafly Trail.

Nike ACG Ultrafly Trail Midsole

A medial view of the Nike ACG Ultrafly Trail featuring Nike’s ZoomX PEBA foam.

Look to the Nike ACG Ultrafly Trail’s midsole to discover the shoe’s standout technology and what truly makes its hefty price tag worth considering. The midsole incorporates Nike’s ZoomX foam, a PEBA (polyether block amide) compound that’s incredibly lightweight and responsive. Found in Nike’s popular Alphafly and Vaporfly marathon racing shoes, ZoomX foam absorbs the impact of each step and then quickly bounces back, giving runners a springy, propulsive feeling with each stride.

This foam is paired with a full-length carbon Flyplate for stability and structure that runners need on technical trails. Nike updated the Flyplate in the ACG Ultrafly Trail by adding a “spine” that allows the plate to flex over roots and rocks. Nike states that this new plate is less stiff than the one in the original Ultrafly.

With both the Ultrafly and ACG Ultrafly Trail in hand, I can bend and torque each shoe to confirm that the new ACG Ultrafly Trail bends more easily at the forefoot and torsionally than its predecessor. However, this difference was less obvious to me on the trails. I loved the original Ultrafly and was satisfied with the balance of responsiveness and stability. I thought the ACG Ultrafly Trail actually felt more stiff and less bouncy out of the box, although I’ve been very happy with the shoe’s performance over time. I ran 30 or more miles at a time in each version of the shoe, and I never had issues with stability on technical trails, strain or unusual fatigue in my feet, or other discomforts.

Nike ACG Ultrafly Trail Outsole

A view of the Nike ACG Ultrafly Trail’s outsole.

The Nike ACG Ultrafly Trail outsole incorporates Vibram Litebase construction to reduce weight and the Vibram Megagrip compound for traction and durability. This combination achieves maximum grip on steep trails, wet rocks, or slippery surfaces without turning a lightweight racing shoe into a clunky hiking boot. It also has a moderate, 3-millimeter lug depth, which is enough to provide grip on wet trails while also feeling smooth on gravel or packed dirt.

I tested the ACG Ultrafly on a wide range of surfaces while running over granite-strewn trails, through shallow creeks, and across lingering snow patches in the high alpine of the central Sierra Nevada, and up and down moondust and loose gravel on my backyard trails in Oregon. This shoe performed as expected, and I trust it while opening up on steep descents, hopping across boulders, or scrambling up peaks.

Nike ACG Ultrafly Trail Overall Impressions

A top view of the Nike ACG Ultrafly Trail.

Overall, the Nike ACG Ultrafly Trail is a worthy consideration for runners who are looking for a high-performance training and racing shoe. It would be an excellent choice for those training for any type of trail race, whether that’s a short, steep, and technical sky race or a cruisier ultramarathon. This shoe’s combination of performance technology and durable materials can handle a wide range of trail objectives.

While this shoe is fun to wear for daily running and workouts, it’s made for racing — with fancy midsole foam, a carbon plate, premium outsole, and a pricetag that reflects the high-end tech and design features. As such, runners who aren’t chasing big goals, training for races, or similarly testing their limits don’t need a trail super shoe. In fact, no runner “needs” a super shoe to achieve their goals. There are tons of great trail running shoes on the market that can help you achieve your goals for probably half the price. That said, if this one’s in your budget, there are many reasons to give it a shot.

Check out iRunFar’s other favorite Nike shoes in our Best Nike Running Shoes guide.

Call for Comments

• What do you think of trail super shoes? Exciting technology or expensive and unnecessary?
• Have you tried the Nike Ultrafly or ACG Ultrafly Trail? What are your thoughts?

Our Favorite Trail Running Shoes

Check out our Best Trail Running Shoes article to learn about our current favorite trail running shoes!