Inov8 TrailFly Zero trail running shoes review: minimalist design for maximum fun on the trails

We’re no strangers to Inov8’s excellent TrailFly family. Inov8 is a British outdoor brand that specializes in creating trail running shoes forged in the English Lake District, the spiritual home of fell running. The fells’ mixture of boggy terrain, rocky ridges and wet climate demands footwear that’ll claw at mud while still holding firm on wet rock. Down the years, the brand's sponsored athletes have included the likes of Barkley Marathons legend Jasmin Paris, Damian Hall, Nicky Spinks and occasional Advnture contributor James Forrest.

The TrailFly family of shoes are some of Inov8's faster offerings, with more of a slant towards speed than the grippier Trailtalon and MudTalon shoes. The latter two are great for damp days on soft terrain in the wild hills and mountains, whereas TrailFly shoes are suited to harder-packed surfaces. However, don’t let this fool you into thinking the TrailFlys don’t cut it in the higher places. I took on a more challenging variation of the UK’s National Three Peaks Challenge wearing the superb TrailFly G 270 V2s and loved every minute.

So, when the lovely Cumbrians at Inov8 landed a message in my inbox with news of a new TrailFly, I was stoked to get hold of a pair and test them out on the trails.

First impressions

The first thing I noticed is that the Zeros have a more generous fit than the snugger, foot-hugging G 270 V2s. The wider toe box is immediately apparent, and I’d say the more relaxed fit makes them a few iotas more comfortable. I didn’t notice any issues due to this on my initial runs. My heel was locked in place and the Zeros felt nicely responsive, with a decent amount of trail feel. They were immediately comfortable.

They're attractive too, featuring the redesigned Inov8 logo that replaced the old one in 2024. I was testing the Blue/Orange version, which makes for a vivid aesthetic, particularly when set against damp, grey hills.

A feature evolution

The TrailFly Zero is, as its name suggests, a zero-drop running shoe. This means that the drop between the height of the heel and the forefoot is 0mm. This isn’t new, the TrailFly G 275 V2 was also a zero-drop shoe.

‘Standard’ running shoes tend to have a drop in the region of 6mm to 12mm, while some maximalist shoes have an even higher drop. As for the high heels worn by Anna De Armas’ Paloma in James Bond film No Time To Die, they clock in with an impressive 105mm drop. Needless to say, while these shoes are clearly ideal for espionage and gut-toting shenanigans, you wouldn’t want to run the UTMB in them…

A zero-drop shoe, like the Trailfly Zero provides something akin to the natural feel of a barefoot shoe, working with your foot towards achieving a more natural gait. The debate around the best amount of drop has raged for many years but, generally speaking, a smaller drop is better for those who strike with the forefoot or midfoot, while a drop of around 6mm or more is better for heel strikers. I personally prefer a lower drop and it’s certainly what I’m used to having worn the G 275 V2s for over a year now. The stack height is 12mm, notably less than the previous shoe, which brings the foot closer to the ground, enhancing the amount of trail feel.

Inov8 says that the new TrailFly Zero has an ‘improved anatomical fit’ thanks to a protective MET-CRADLE that locks the heel and midfoot in place when laced up, keeping everything nice and secure. Unlike the G 275 V2s, the tongue isn’t fully gusseted, so debris can invade the inner sanctum of the shoe.

As mentioned, the toe region is roomier, allowing plenty of space for splayed digits. I’d say the Zero feels less restrictive than its predecessor on the whole. I was testing the Standard version, as I have relatively narrow feet. Those with wider feet or those who value loads of toe space can also opt for the Wide version.

The Zeros deploy Inov8’s Boomerang footbed, a cushioned insole that uses compressible TPU beads to retain energy, The idea is that the footbed releases the energy, propelling the runner forward. Inov8 say that the design has been 'rigorously tested' for long lasting performance. The midsole utilizes the brand’s Flyspeed Pro foam to cushion the ride. Working in tandem with the footbed, it’s designed to maximize energy return while absorbing shocks from the ground beneath your feet.

Inov8 have spent a long time hammering home the message that the Graphene it uses in its outsoles is 'the world’s strongest material' and they’re at it again here. In my experience, Inov8’s trail shoes do last longer than much of the competition. I’ve been through several pairs of Salomon Speedcross shoes in my time. I've watched as their lugs have ground to nothing but imprints of where a proud gripper once stood. This hasn’t been the case with my Inov8 pairs, which have stood the test of time admirably well. Maybe there's something in this Graphene business after all...

And so, to the design of the outsole, which is substantially different to the previous iteration. The lugs are still 4mm deep, which suggests a good amount of traction on soft terrain but not as much as with the deep mud-gripping claws you get on some. However, the previous array of T-shaped lugs has been usurped by a more numerous, aggressive array of chevron-shaped lugs, with a much more obvious braking zone towards the back of the shoe. There are also flat-topped lugs at the front and back, which provide more surface area when in contact with bare rock.

Unlike the G 275 V2s, the Zeros feature a heel loop. This allows you to clip them into a carabiner or hang them off a hook, should you wish.

The shoes weigh somewhere in the region of 9.7oz (274g) per shoe (US 9 / UK 8). I say in the region of, as I weighed my brand-new pair and the right shoe came out as 9.9oz (282g) and the left shoe was 9.5oz (269g). Curious weight differences aside, this makes them a fairly light option, though even lighter trail running hooves exist if you’re obsessed with every ounce when it comes to race day.

Taking to the trails

I’ve been testing the TrailFly Zeros on my local Bristol trails and in the hills of the Bannau Brycheniog (Brecon Beacons) National Park during the late spring and early summer months. Britain enjoyed a prolonged dry spell during the test period, though towards the backend I was able to enjoy a few wetter runs on soft ground, both in Bristol and on the pens of South Wales. They performed well regardless of whether I was pounding rooty woodland trails, packed gravel, grassy hillsides, or rocky ridges.

Broadly speaking, I found the Zeros just as capable and fun to run in as the G 270 V2s. Fit wise, as alluded to, they feel roomier, which makes for greater comfort. Despite not fitting quite as snugly, I had no issues with the heel slipping and the fit felt secure throughout. Neither did I didn’t notice any issues with breathability, even when running in temperatures of between 70 and 86°F (20 and 30°C).

The cushioning is about right for me – I like to be able to feel and respond to the trail and I’m not so much of a fan of maximalist shoes. Inov8 say the Zero is 'perfect for everything from trail intervals and fartleks, though to ultramarathons', but I think, for really long distances, some may prefer the additional cushioning of the new TrailFly Max.

When it comes to the really rocky stuff, the Zero’s new features bring both improvements and ‘even better ifs’. I have no doubt that the outsole is far better suited to scrambling terrain. Towards the front, there are 9 flat-topped lugs, which provide a good deal of surface area for techniques like smearing when negotiating angled slabs.

There’s noticeably more flat rubber at the very tip of the shoe too. It’s not quite the ‘climbing zone’ you see on approach shoes, but it’s a step in that direction. This provides a little more security when edging across rock. Likewise, the back of the outsole features four flatter platforms, ensuring a decent hold whenever I struck with my heel while hopping from boulder to boulder.

The ‘even better if’ – and I’m really nit picking here – is that their fit feels slightly less precise than the previous iteration. It’s only a minor thing but the roomier toe box makes them feel slightly less secure on technical rock sections – though this is compensated for by the improved design of the outsole.

Off the rock and back on the sloppy stuff, I felt more confident when bounding downhill in the Zeros than in the G 270 V2s. The back half of the outsole has a more aggressive braking region, with 13 angular, chevron shaped lugs as opposed to the previous iteration’s nine T-shaped offerings. Although I’m yet to test the Zeros in winter, I’d imagine they’d grip better than previous iterations based on all of this – but I’d still prefer the aggressive lugs on something like the TrailTalon for this kind of thing.

However, for your standard sort of trail runs on hard-packed ground, Inov8 have done it again with the TrailFly Zero – a super, minimalist shoe that you'll get plenty of use out of.