Inov-8 Rocfly G 390 Review: A Lightweight, Nimble Hiking Boot for Tackling Any Terrain
By Contributor Ryan Flugaur and Social Media Wizard Bach Pham
The Rocfly G 390 works to blend the comfortable and lightweight feel of a trail shoe with the protection and ruggedness of a trail boot. This was my first time in an Inov-8 shoe and I really enjoyed my time with it. Living in central Wisconsin the terrain is mostly flat, rocky, and wooded, however, about 30 minutes North of my hometown lies Rib mountain state park. This is Wisonsins biggest “hill” coming in at 1,942 feet but is dwarfed by many other true mountains throughout the rest of the United States. I was able to take the Rocfly G 390 out multiple times in a variety of conditions varying from flat muddy trails to steep rocky inclines. This shoe is designed to be a bouncy hiker that blends the worlds of trail running shoe and hiking boot and does a pretty good job doing so.
Inov-8 Rocfly G 390Price: $210 via Inov-8
Weight: 13.8 oz, 390 g (men's size 9)
Stack Height: 25 mm heel, 19 mm forefoot
Lug Depth: 4 mm
Drop: 6 mm
Classification: Lightweight Hiking Boot
RUNNING SHOE SUMMARY
Ryan: The Rocfly G 390 is a lightweight hiker best suited for harder surfaces such as rocky terrain, gravel paths, and roads. I had no issues while trekking up a steep incline over large rocks and boulders. The mid-height collar feels secure and lightly padded for extra protection. It offers a softer ride with a smooth transition from initial contact to toe off. The breathability of the upper allows it to be worn in a variety of conditions ranging from light rain to warmer sunny days.
FIT
Ryan: The Rocfly G 390 fits me true to size in my men’s size 9. It is built on a wide last and given a fit score of 5 by Inov-8. This scale is used to classify the width of the toe box with 5 being the widest. This extra width in the boot allowed me to wear a padded wool sock while other times switching to a thin running sock. Even while wearing the thinner sock, the boot felt secure enough to take off-road. The lacing system does an adequate job tightening up the boot when going with the thin sock. I liked the flexibility to change sock thickness based on the outside temperature as well as my activity level in the shoe. This can be difficult for me with certain running shoes as the toe box is often too narrow to wear thicker wool socks on cold days. The tongue is gusseted by a piece of stretchy nylon that helps to hold it in place. It is lightly padded to give some protection from the laces as well as from the hiking environment. The heel has a semi rigid heel counter that is adaptable when ambulating over uneven surfaces and feels secure without slippage.
The upper is constructed of a water resistant flexible knit upper. This may benefit those that hike in the rain as the upper material will likely dry out faster. I took the boot out in a light snowfall and my socks stayed nice and dry. Typically, when a boot is waterproof not only does water have a hard time getting in, but also getting out. This may make it harder for moisture inside the boot to escape and add to dampness inside the hiker. The improved breathability of the water resistance material also means the shoe will feel better in warmer environments. When wearing the Rocfly G 390 for the first time, I noticed that the upper felt a little stiff and had a small pinch in the fabric over the dorsum of my toes. On subsequent hikes, this became much less noticeable as the material broke in.
Bach: The Rocfly G 390 is a very accommodating fit that runs true to size. There is ample room in the mid to forefoot to splay and give your foot space to swell through a long hike. The soft knit upper further helps with expanding as needed. The lacing system provides good lockdown throughout. I was able to get dialed-in with relatively little effort out of the box which I appreciated. I would say though that as tight as I could get it, compared with some higher priced leather hiking boots I've used the lockdown was average here, further contributing to the nimble feeling of the shoe but affecting stability which I'll discuss later.
I found no break-in time needed - the G 390 felt great out of the box and only got better with each hike. The upper is soft and plush, providing a very comfortable experience for all day hiking. The G 390's knit design is breathable for warm days and suitable enough for cooler days at keeping your feet warm. Like Ryan mentioned, you can fairly easily swap sock styles with this pair and have little issue thanks to the well-fitting upper, adjusting as needed to the weather. Due to the boot being non-waterproof, it not only breathes well but also contributes to that overall weight reduction. If you expect good conditions on your hike, this is going to be a great boot to strap on and go year-round.
PERFORMANCE
Ryan: The Graphene-infused G-FLY foam on the Rocfly G 390 is soft yet stable enough to endure some pretty rough terrain. This lightweight hiker comes in at 390 grams (13.76 oz) with a 6 mm drop which makes it a good choice for all day hiking. I was able to wear them for 10 hours continuously during a variety of activities ranging from a 5 miles hike up a steady incline trail, 2 miles of road walking, and general outdoor activities. I was surprised at how bouncy the G-Fly foam felt underfoot. It even felt comfortable when performing other activities than hiking such as walking over flat blacktop roads. These are activities I typically wouldn't perform in traditional hikers as they typically feel too heavy and unforgiving.
The Graphene-infused G-FLY foam was something I had not heard of before testing out this hiker. Inov-8 claims that the G-FLY graphene foam is 50% stronger, 50% more elastic and 50% harder wearing. Those are some pretty bold claims and difficult to quantify and test. After digging a little deeper, I discovered graphene is a material constructed from graphite with some pretty cool properties. It has been shown to be 200-300 times stronger than steel while still remaining flexible. I have yet to truly test the full durability of the G-FLY foam, but it displays very little wear despite many hikes and miles in the shoe. I expect this foam to last for many miles even when used over rocky or unforgiving surfaces.
On the road and trail, the traction of the Rocfly G 390 is superb. I had no problems navigating over rocky trails as well as gravel and dirt. I also tested the hiker on walks with my dog on a crushed gravel and sand trail. Large rocks and uneven surfaces are no issue for this hiker as the Adapter-Flex groove allows the boot to mold to uneven terrain. The benefits of the groove became even more obvious when I hiked off the trail, marching over stumps, logs, and other large rocks. I felt the boot adapt to the uneven surfaces below me keeping my foot stable and planted. One area I feel the boot struggled was over wet and muddy areas as the 4mm lugs do not grip well enough.
Bach: 13.76 g might seem like a lot in running shoe terms, but in terms of hiking boots this is like throwing a 7 oz racing flat on. The Rocfly G 390 is nimble and one of the best moving boots I have ever tested. Between the bouncy graphene midsole and slight rocker, you can really hustle and bustle. There are points on hikes where I was barrelling down trails, almost to the point of running thanks to how effortless the shoe maneuvers. Being one of the lightest hiking boots I have used, I found it to be fantastic on day-long hikes. It's no surprise that Inov-8 athlete James Forrest broke the world record for a self-supported 500 mile hike, completing his journey through Scotland's Ben Nevis, England's Scafell Pike, and Wales Snowdon mountains in 16 days, 15 hours, and 39 minutes with the Rocfly G 390.
The shoe features an "Adapter Flex" groove in the midfoot unique to Inov-8. I was worried that it would cause some instability or awkwardness on the trail, but I honestly never noticed it during my hikes. The shoe features enough rigidity through the midfoot that it wasn't an awkward sensation and I do feel like it allowed me to adapt to awkward terrain. The G 390 also has a surprising amount of flexibility for a hiking boot that makes it almost feel like a trail runner, which I think runners will find very appealing.
While the outsole has fairly good traction for gripping varying terrain on dry days, I did feel on some very wet surfaces it was slick. Chief Editor Matt Klein found this to be also true in the Ultra G 300, and it remains an issue here: the grip doesn't handle overly wet, slick surfaces like rocks and deeply muddy trails well. I would definitely proceed these areas with caution and if you know you're going into a wet all-day hike scenario, look towards a more heavyweight boot to keep you protected.
As far as durability goes the shoe has held up well with no wear seen so far in my two months of testing. We will report back later in 2022 with a bigger durability report, but my initial impression is that this will still be somewhat average in terms of hiking boots - especially when we're talking about heavy duty leather boots that can take a tremendous beating. While durability is average, you get in return here all the nimbleness and breathability which I think is tremendously valuable for my needs living in the humid American South and something I could look past.
STABILITY
Ryan: The Rocfly G 390 offers the stability needed to traverse technical terrain while being nimble enough for a walk down the road. The collar of the boot rises up the sides of the ankle providing structure and support. The mid and forefoot are wide with a full contact outsole adding to the stability of the hiker. The collar and upper are constructed of a thick knit that also adds to the stability of the hiker. The Flex groove in the midsole does mildly affect the stability of the boot however with lower impact exercises such as hiking, it will likely not impact it too much.
Bach: The Rocfly G 390 has average stability for a hiking shoe due to the nature of its weight. Being a lighter shoe, it naturally is less stable when finding footing and grasping complicated terrain than a heavier, more protective boot. The boot is also surprisingly flexible which, while adding comfort, further destabilizes the shoe where typically rigidity can often help with going through rocky terrain or wet/snowy conditions. Between the boot's flexibility and lightness, there is a slightly less confident step in the Rocfly compared to heavier boots. I found myself slightly wanting to roll my foot on one or two occasions as I misstepped on uneven terrain covered by leaves while flying down a trail. Overall I would say the Rocfly, if labelled in running terms, is a fairly neutral hiking boot.
That being said, most day hikers and weekend trippers visiting state parks and clean trails will likely find the Rocfly more than enough for their needs. The stability factor really plays most if you plan on tackling longer hikes where conditions are difficult to expect or very technical climbs. On the vast majority of my time in the boot, I found it to be a comfortable pleasure tackling my state parks and local trails.
THOUGHTS AS A DPT / FOOTWEAR SCIENCE
Inov-8 claims that the Rocfly G 390 delivers 25% greater energy return thanks to its unique Graphene-infused G-FLY foam but what does 25% greater energy return actually mean to you? To answer this question we will do some digging into foam properties and the definition of energy return and how it relates to an improved economy. Mizuno, as well as other companies, lab test their foam using a variety of measures and then scientifically prove certain characteristics of the foam including softness and response. For example, when Mizuno released their new Mizuno Enerzy foam, they claimed it was 15% more responsive than the previous U4ic foam. Despite the increase in 15% responsiveness we can reasonably assume we will not see a 15% improvement in the wearers running economy. Running economy is tested in a lab using a metabolic cart and there are many studies showing improvement in running economy for certain individuals and shoes. Thus far, there has never been a foam or shoe that has improved running economy even close to 15%, with the Vaporfly improving running economy for some runners by around 4%. So getting back to the question “what does 25% greater energy return actually mean?”, probably not as much as you might think. You may notice that the foam is more bouncy and comfortable when hiking up the trail, however, you will likely not notice an improvement in hiking economy. - Contributor Ryan Flugaur
RECOMMENDATIONS
Ryan: One thing I think could be a good addition to the Rocfly G 390 is a gator attachment system. This would become useful when navigating terrain with a lot of rocks and debris where you may need some extra protection and may allow the hiker to be used for longer, more rustic hikes.
Bach: I think it would be worth considering adding some wider lugs through the mid forefoot on back to help with wet, muddy paths. It does terrific as is in dry terrain helping maneuver you through pretty much anything, but when it comes to slick wet surfaces like rocks or very wet muddy trails, it can get pretty slippery. I think shoring up this area would help buyers distinguish the G 390 over trail running shoes which some may be opting for their day hike.
WHO THIS SHOE IS FOR
Ryan: The Rocfly G 390 is a lightweight, bouncy, and flexible hiker best suited for day hiking but I feel like it can be used on longer overnight hikes. The minimal weight of the boot reminds me of a trail running shoe but with added protection in the midsole and a thicker upper which sets it apart. The hiker performs great over a variety of surfaces but excels on hard rocky trails as well as roads. The G-Fly graphene infused foam seems very durable and should last many miles and hikes.
Bach: Inov-8 designed an incredibly fun, lightweight hiking boot with the Rocfly G 390. For the average hiker who wants a hiking boot for a day hike or weekend hikes, this is absolutely worth a look. It's fast, breathable, and extremely comfortable, which are features that will also appeal to more seasoned hikers too who want something a little different in their collection. The price point of $210 may seem steep, but I think fits when you look at the competition. The mid-$200s is where you begin seeing leather options along with Goretex boots for all-weather hiking. For someone who is wanting to take a next step from average hiking boots, the Rocfly G 390 is both different and exciting enough to make the price difference feel worthwhile. Anyone who wants a hiking boot for both recreational and professional use, they should definitely consider their needs and likely look towards a more traditional boot that's more reinforced and durable. But for anyone looking for an excellent boot to do some nice distanced hikes in thanks to it's high level of comfort and mobility, you'll want to put the Rocfly G 390 on your short list.
GRADING
Ryan
Fit: A- (Appreciate the wider toe box and last which did
allow me to wear a thicker wool sock, upper was a bit restrictive at the
beginning but stretched out after a few hikes)
Performance: B+ (Great traction and ride. Performance in wet conditions lower the grade)
Stability: A- (Very stable boot with wider midfoot and protective knit collar)
DPT/Footwear
Science: B+ (The graphene infused G fly foam is really cool with its
durability properties and improved energy return but I am unsure if this
new technology will improve the hike for the average individual )
Personal: A- (I really like the Rocfly G 390 as a lightweight hiker and will continue use it throughout the winter)
Overall: B+ (Overall a great lightweight hiking boot with added protection over a trail running shoe.)
Bach
Fit: A- (Accommodating fit that's breathable and easy to get a good lockdown)
Performance: A- (Fast, nimble, and fun as promised with a uniquely bouncy midsole)
Stability: B (Lightweight structure and design makes it feel less stable than typical hiking footwear that's heavily reinforced, espcially for wet conditions)
DPT/Footwear Science: A- (Implementation of running footwear design into hiking makes the ride of this shoe unique)
Personal: A- (An absolute blast for me and very suitable for humid American South weather)
Overall: B+/A- (For the recreational hiker, an excellent hiking boot that will likely tick all the boxes)
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FURTHER READING
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On Cloudflow v3 - A new sustainable upper and outsole helps revitalize the lightweight trainer
Mizuno Alpha Eco Apparel - Super light performance clothing with sustainability and the future in mind
Adidas Adistar Review - Former stability star returns with a super stable platform and new foam for Adidas
Find all Shoe Reviews at Doctors of Running here.
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TESTER PROFILES:
Ryan Flugaur, PT, DPT, TPI
Certified Doctor of Physical Therapy
Dr. Flugaur began running four years ago when he was looking for a change to his current exercise program of body building. He continues to do some light strength training but running has become his true form of exercise to stay healthy. He has met some great friends through running and loves the camaraderie that the running community brings. He typically runs 20-40 miles a week depending on his training schedule. Dr. Flugaur lives in Wisconsin with his wife Olivia and 2 kids, Lucy and Jack. When not running he enjoys mountain biking, fat biking in the snow, camping, and cheering on the badgers, brewers, and bucks. PRs Include: 5K:20:05 (2021), 10 K: 43:36 (2021), Half-Marathon 1:42:22 (2021)
Marketing and Social Media Manager
Bach Pham is a 140 lb male with PRs of 23 min 5K, 52 mins 10K. He typically runs between 25-35 miles per week at a variety of paces between 8:30 (tempo) -10:00 (recovery) min/miles. He typically prefers shoes that provide some mild to firm cushioning underfoot that is lightweight and responsive. Currently his goals are to complete the half and marathon distances.
Editor's Note: As always, the views presented on this website belong to myself or the selected few who contribute to these posts. This website should not and does not serve as a replacement for seeking medical care. If you are currently injured or concerned about an injury, please see your local running physical therapist. If you are in the Los Angeles area, I am currently taking clients for running evaluations.
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