Inov-8 TrailFly Zero Review
The Inov-8 TrailFly Zero is the latest addition to the British brand’s TrailFly series, designed to perform best on hard-packed trails. It replaces the Inov-8 TrailFly G270, another zero-drop trail shoe made for similar terrain. Like its predecessor, the TrailFly Zero features a zero-drop platform, meaning the heel and forefoot sit at the same height. Combined with a broad, rounded toe box, this promotes a more natural running experience by allowing the foot to spread, engage the plantar fascia for cushioning and propulsion, and encourage full-body alignment. This natural movement can help reduce stress, improve posture, and lower the risk of injury.
Thanks to advancements in midsole technology, the TrailFly Zero offers a slightly softer and more flexible ride than the G270. This flexibility is essential, as it enables the shoe to move with the foot rather than forcing the foot to conform to a rigid structure. Since everyone’s foot shape and arch length varies, a natural ride means each runner can land and transition based on their anatomy—not on a pre-defined flex point.
The midsole is constructed from Inov-8’s FlySpeed Pro foam, a supercritical EVA that delivers greater energy return than the midsoles in the standard TrailFly and TrailFly Speed. It also enhances flexibility, helping both the foot function naturally and the shoe adapt to uneven terrain. This flexibility makes for smoother progress on broken ground and slopes, as the shoe can contour to the surface beneath it.
The outsole uses Inov-8’s sticky rubber infused with graphene. This innovative addition makes the rubber more durable and elastic, giving it the flexibility to conform to terrain without sacrificing longevity. Sticky rubbers typically offer great grip on wet surfaces but wear quickly. By adding graphene, Inov-8 has created an outsole that balances grip and durability, making it suitable for road-to-trail transitions while still delivering reliable traction on wet rock, roots, and wood.
The 4mm lugs are flat and designed for firm terrain, providing solid grip on tarmac and smoother trails without being intrusive underfoot. You can’t feel the lugs when running on the road, and the ride remains smooth. These lugs also offer decent traction on softer trails, making the shoe a great option for mixed terrain runs that include bridleways, single track, and occasional mud. While the grip won’t match an 8mm lug on deep mud, it outperforms many shoes with similar lug depths. This is due not only to the lug pattern but also to the TrailFly Zero’s flexibility and ground feel, which help increase the surface area in contact with the ground and allow nimble movement over tricky terrain.
Like the rest of Inov-8’s latest range, the TrailFly Zero features a wide, rounded toe box to allow feet to spread and function naturally. It comes in both standard and wide fits. Even the standard fit is generously shaped, offering plenty of volume in the forefoot. This room is essential in a zero-drop shoe—if the foot can’t spread on impact, the Achilles and calf must work harder to compensate, often leading to soreness. Choose a width that allows your toes to move freely and your feet to splay comfortably. If you usually wear wide-fit shoes, the wide version of the TrailFly Zero is likely your best option.
Despite the roomy forefoot, the fit is secure. The heel cup is lightly padded and flexible, reducing water absorption while adapting to your heel shape for a snug fit. In some zero-drop shoes, the heel can collapse under pressure, but I haven’t found this to be an issue with the TrailFly Zero. Its flexible midfoot allows the shoe to bend naturally with the foot instead of resisting movement.
Midfoot overlays wrap around the foot when laced, providing a secure lockdown. Even with ample space in the toe box, your foot stays firmly in place—even during steep descents. The tongue is made from a soft, thin material with a central strip of zonal padding to shield the foot from lace pressure. It’s gusseted to prevent debris from entering and features a lace loop to hold it in place during runs.
A protective overlay wraps around the base of the upper to shield the engineered mesh from abrasion and dirt. It extends into a toe bumper that offers solid protection without compromising flexibility or comfort.
For a trail shoe to encourage nimbleness and foot engagement, it must deliver good ground feel. That doesn’t mean it should feel harsh or un-cushioned, but it should allow you to sense the terrain. The TrailFly Zero’s 12mm midsole is made from a responsive foam with minimal compression. This stimulates the foot to spread and adapt as it contacts the ground. Complementing the midsole is a new, lighter version of Inov-8’s Boomerang footbed. Nitrogen-infused to prevent air loss and dirt ingress, the Boomerang foot bed maintains its slight bounce and doesn’t degrade over time. At just 6mm thick, it adds noticeable comfort without muting ground feel.
The shoe weighs 270g in a men’s UK 8, the same as the G270. However, thanks to its flexibility and natural ride, it feels lighter once you’re moving.
In terms of sizing, Inov-8 is similar in length to La Sportiva, Hoka, New Balance, and Karhu. If you’re used to Brooks, Saucony, 361, Altra, or Topo, consider going up half a UK size in Inov-8 to achieve a similar fit. For example, a UK 11.5 in Inov-8 is roughly equivalent in length to a UK 11 in Brooks.
I find zero-drop shoes make it easier to manage my pace. Without a high heel or aggressive rocker pushing me forward, I can jog along steadily or pick up the pace when needed. Downhill sections feel natural with a quicker cadence, and the absence of an elevated heel improves posture and responsiveness to the terrain. If you’re new to zero-drop running, it’s wise to ease into them gradually. Start by alternating with your current shoes to allow your feet and lower legs time to adapt and recover between sessions.
Personally, the natural feel of a flexible, zero-drop trail shoe is addictive—especially when running over undulating ground where you can feel every contour and move in sync with the trail.
Conclusion
The Inov-8 TrailFly Zero is a versatile trail shoe, built for hard-packed trails but equally capable on broken terrain and even tarmac. It offers natural foot function, excellent grip, and a secure yet accommodating fit. With improvements in cushioning, flexibility, and ground feel, it’s a worthy successor to the G270 and a strong option for trail runners who value performance without sacrificing connection to the ground.
Other Considerations
Altra Lone Peak 9+: The original zero drop trail running shoe. A touch more volume in the toe box with a firmer ride. Not quite as flexible but, has a slipper like comfort that is hard to explain. The stiffness makes them feel slower and less responsive. So, they don’t feel as fast and nimble as the Trailfly Zero.
https://www.northernrunner.com/blog/altra-lone-peak-9-review/
Topo Pursuit 2: A similar level of traction on hard packed terrain. The Pursuit is a bit more grippy in the mud but stiffer with more cushioning. This takes away some of the ground feel and makes them less nimble than the TrailFly Zero. https://www.northernrunner.com/blog/topo-athletic-pursuit-2-review/
Altra Superior 7: The Inov-8 TrailFly Zero is a mix between the Lone Peak and the Superior. They are more flexible than the Lone Peak but, not quite as much as the Superior. Underfoot protection and grip is more similar to the Lone Peak as is the amount of volume in the toe box. https://www.northernrunner.com/altra-m86/superior-t108
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