Inov8 TrailFly Max review: This classic shoe gains a massive stack

In 2024 I wore the older Inov8 TrailFly trainers on a crazy ultra-marathon, setting a self-supported FKT (fastest known time) on the 175km Cleveland Way, in a non-stop time of 28 hours 12 minutes. I loved them – they worked really well for me and kept my feet happy over very long distances.

But, if I had one criticism for those distance-oriented trail running shoes it was the lack of underfoot cushioning. They prioritised ground-feel over bounciness, and I probably could have done with more energy, rebound and speed.

But now my prayers have been answered, with the new-for-2025 release of the TrailFly Max. Inov8 has taken the best-selling TrailFly original and supercharged it with a "generous slab" of new FlySpeed Pro foam for a "comfortably cushioned yet naturally responsive ride".

Is this Inov8’s best ever shoe for big mileage runs and ultra-marathons on hard-packed trails? Here are my thoughts.

Upper and waterproofing

This shoe is not waterproof and, at present, is not available in a waterproof version. But this is a sensible approach for most trail runners – trying to keep your feet dry can be a futile task when crossing waterlogged moorland or boggy hilltops, and instead it’s better to prioritise breathability and a quick-drying design to maximise your chances of avoiding blisters and sore spots.

The upper of the Inov8 TrailFly Max is constructed from a single piece of air-mesh material with overlays of Met-Cradle strips (a TPU-like reinforcement) – these give added durability where you need it, as well as a “locked-in, secure feel” that pulls in from the midfoot to the heel when the laces are tightened. You also get an extra bit of robustness at the toe bumper.

All-round comfort levels are very high, including straight out of the box. The upper is soft, forgiving and wraps the foot nicely, with your heel held nicely in place without any slippage.

If comfort is your big priority, you can’t really go wrong with the TrailFly Max. However, the flip side is that these shoes are lightweight (292g per shoe, men’s UK 8, standard width) and not exactly the most sturdy or robust.

This may mean long-term durability is compromised compared to heavier pairs (how many prolonged batterings on gnarly rocky terrain will the upper withstand?), but – of course – the trade-off is that you get a far faster, comfier, lighter and more agile trainer. For me and many other trail runners, that’s a fair exchange and a price you’re willing to pay.

In terms of the shoe’s fit, comfort levels are significantly improved – in my opinion – thanks to Inov8’s new NaturalFit shoe last. Introduced in 2024, the brand now makes all its footwear with this natural, foot-shaped design that locks in at the heel-midfoot and widens at the toes.

Developed through extensive athlete and customer feedback, this new shape is designed to "allow the foot to function naturally". Personally, I get on well with this.

I particularly like the wider toebox, which allows my toes to naturally splay and spread out. This is crucial for big mileage adventures, where an overly restrictive or tight toebox can lead to blisters, pinch points and rubbing.

I had a pair in the ‘standard fit’. There is also a ‘wide fit’ available. The difference between the two is in the width across the toebox.

Midsole

The midsole is the key feature that makes the TrailFly Max stand out compared to the other three shoes in the collection, including the TrailFly (which I wore on the Cleveland Way in 2024), the race-ready TrailFly Speed and the brand new zero-drop TrailFly Zero.

The Max in the name refers to the maximalist cushioning you get in this shoe’s midsole, making it easily the most cushioned shoe in the range. In fact, it’s probably Inov8’s most cushioned trail shoe ever, enabling you to “fly over the ground” with rapid forward propulsion and a bouncy feel.

Personally I love the approach – the plush cushioning adds a sense of comfort, speed and energy to your movements, without losing that underfoot connection to the ground, and for big mileage runs this might be my favourite ever Inov8 trail shoe.

The midsole is made from a super-critical, nitrogen-infused foam, which Inov8 calls FlySpeed Pro. The brand says “this hard-wearing foam provides a great balance between cushioning, ground-feel and stability over uneven terrain” and is “ideal for when you need sustained comfort and support when ticking off big miles”.

Inov8 has put 24mm of the lightweight midsole foam at the heel and 18mm in the forefoot. The overall stack heights (floor to foot) are 35mm at the heel and 29mm at the forefoot, resulting in a 6mm drop.

Alongside the midsole, the Boomerang footbed (insole) of the TrailFly Max adds to the sense of rebound and energy. Each insole features hundreds of foam beads which, according to Inov8, compress and spring back for 40% more energy return during each stride.

It’s nigh on impossible to objectively judge what difference this specific feature really makes (I haven’t tried using the shoes without the insoles), but overall I can say that the TrailFly Max does feel nicely cushioned with good forward propulsion.

Some runners might question why go for this shoe, when other brands such as Hoka have more of a pedigree when it comes to maximalist cushioning.

Indeed, if you want a highly-cushioned, technical trail shoe, there are loads of options out there with maximalist midsoles and higher stack heights than the TrailFly Max, such as the Asics Trabuco Max 3 (43mm, 38mm) and Hoka Stinson 7 (42mm, 37mm).

It’s also true that if you want pure speed for ultra-marathons, a trail shoe with a carbon plate (or rods) such as the Adidas Terrex Agravic Speed Ultra or The North Face Summit Vectiv Pro 3, will probably feel more like a PB-smashing speedster.

However, Inov8 would argue that its approach provides the best of both worlds. It’s not all about ridiculous levels of pillow-y soft, cloud-like underfoot cushioning.

Instead the TrailFly Max is designed to provide the best of both worlds: good levels of cushioning, but also with a "naturally responsive ride" and "plenty of agile ground-feel". For many it’ll prove a perfect balance. But if you just want pure maximalist cushioning, perhaps look elsewhere.

Outsole

Inov8 is nothing if not competent when it comes to outsole grip. Indeed, the brand has built its gnarly fell running reputation on solid underfoot bite and traction – and you could even say grip is part of Inov8’s DNA.

This skill and expertise is clear to see in the TrailFly Max, which features Inov8’s G-Grip graphene rubber outsole with 4mm studs.

These are “carefully positioned in multiple directions to improve grip, shed debris quickly, boost propulsion off your toes and help you brake at the heel”, as the brand confidently puts it, adding that this version of graphene-enhanced rubber is the best yet, providing “extra grip in wet conditions” compared to previous models.

Graphene is the world’s strongest material and, according to Inov8, the graphene outsole “cuts through loose trail and remains super-durable, but also gives improved grip in wet conditions”.

On initial impressions, I’ve found the grip to be impressive, giving me confidence over mixed terrain and I certainly don’t have any complaints. I would say that the 4mm lugs clearly aren’t as aggressive or deep as other Inov8 shoes designed for muddy, wet, steep ground, such as the excellent Inov8 MudTalon.

But that type of extreme sloshiness isn’t what the TrailFly Max are designed for. Instead they're made for longer runs and ultra-marathons over more hard-packed, rockier ground, particularly in spring and summer.

Price and performance

Available for £150, the Inov8 TrailFly Max is fairly priced within the overall market for top-tier trail shoes. It’s neither a total bargain nor a rip-off, and instead the price is appropriate and affordable compared to many competitors.

In my opinion, performance is excellent too: the graphene-infused outsole grip is reliable, the fit is comfortable and locked-in, all-day comfort levels are high and the maximalist cushioning feels energetic and bouncy for big mileage adventures like ultra-marathons.

Verdict

If you’ve always loved Inov8’s trail running trainers for their ground-feel, grippy traction and underfoot responsiveness, but wanted more maximalist cushioning, bounce and energy, then the TrailFly Max is here to answer your wishes.

Designed specifically for ultra-marathons and big mileage adventures over hard-packed trails (as opposed to super sloshy and sloppy mud), these trainers are set to become a new favourite.

About the author

James Forrest is a prolific peak bagger and long-distance runner who’s one of the most high-profile outdoor writers in the UK. He writes regular features and route guides for Trail and has been one of our main gear testers for the last few years.

James is based on the edge of the Lake District so when he isn’t off on his latest crazy adventure or challenge, he’s running in his local fells. James reviews every type of outdoor kit for Trail and is a real authority on everything you need for long distance running gear.