- Weight: 293g (M), 234g (W)
- Stack height: 42mm (heel), 38mm (forefoot)
- Drop: 4mm
Pros
- Plenty of underfoot cushioning
- Grippy Vibram outsole
- Plush padding on heel collar and tongue
- Breathable upper
Cons
- Not for muddy trails
- You want a nimble shoe for technical trails
The shoe
The New Balance Fresh Foam X Hierro first launched in 2015 and has been steadily evolving ever since. Now at version nine, this high-stack cruiser combines New Balance's Fresh Foam X cushioning to support weary legs with a Vibram outsole for underfoot confidence. Notable updates to the latest version include an even higher stack (42mm in the heel) with a dual foam midsole, a roomier toe box and an improved outsole.
Ahead of Race to the King — a 100km ultramarathon across the South Downs — I was torn between two trail shoes: the ever-popular Hoka Speedgoat 6 or these. In the end, I put my faith in New Balance and the promise of cushioned comfort over long miles. Would the Hierro v9 carry me through unscathed, or would they cost me a toenail (or three)?
How does the Hierro v9 fit?
While the toe box on the Hierro v9 has been re-designed to feel less restrictive than the v8, sizing still runs on the small side. I initially opted for a UK 8.5, but having completed some longer training runs in the shoe (including a 40km run...as you do...), I wanted a smidge more space for race day and went up to a UK 9. This proved to be perfect, so I'd recommend going up half a size. It's worth noting, however, that for some reason the shoe maxes out at a UK 8 in the women's version. I had to go for the men's shoe to get a UK 9.
What everyone's reading
When it comes to comfort, there's ample padding around the heel collar, particularly on the very back of your Achilles. The tongue is particularly gusseted, with plenty of padding there, too, ensuring you don't get any pressure on the top of your foot from the lacing system. Overall, the foothold is good, feeling snug through the heel and midfoot, and with a moderate amount of room in the forefoot — not too generous, but not too restrictive. The knit upper looks like it'll run hot, but I found it to be plenty breathable during my ultramarathon (which happened to fall on one of the warmest days of the year). Finally, you've got a heel tab for easy on/off — handy if you're changing your shoes mid-race.
A word on stability: the Hierro v9 has a wide base. This offers great support on uneven ground and helps you to feel planted over long distances, especially when fatigue sets in. However, on tighter, twistier trails, that broader platform (and considerable stack height) can make the shoe feel a touch less nimble — something to consider if you favour technical routes where agility is key.
What’s it like to run in the Hierro v9?
If you’re after a lightweight and nimble shoe for tackling technical mountain terrain, you won’t find it in the Hierro v9. But if you want a cushioned cruiser that combines the underfoot comfort of a road shoe with the reassurance and grip needed for trails, it’s just the ticket. In fact, I think this is one of the only truly hybrid shoes on the market, along with Hoka's Challenger 8: one that feels protective on road, but grippy and connected on the trails.
That is largely thanks to the midsole’s generous portion of Fresh Foam X – 42mm in the heel and 38mm in the forefoot – split into two different densities: you've got a more comfortable and compliant foam directly underfoot and a firmer layer of directly above the outsole. The effect is a springy yet stable ride that keeps the legs ticking over during long days – including my 100km ultra. I expected to pick up the odd blister or two over the course of the day – which saw me running for around 13 hours – but incredibly, I only suffered a very minor hotspot (which didn't actually turn into a full blister) on the bottom of my big left toe. Huge kudos to New Balance: these really are built for the long haul. (And shout out to SUMS running socks, too, which I'm sure played a role).
My only criticism is that my foot didn't feel totally secure around the midfoot – I had to stop to synch the upper in at around 60km (and probably should have stopped sooner). I'd put this down to the fairly roomy fit of the shoe overall which, while great for swelling feet, feels a smidge too wide.
Like the v8, the outsole features gold-standard Vibram Megagrip for unparalleled traction, while the 4.5mm lugs are capable of tackling all but super technical or very muddy terrain. For the latter, you'll want something that can clear mud more easily – the lug pattern on the Hierro v9 definitely isn't designed for sludge.
RW verdict
A plush and protective trail shoe that shines over long distances and mixed terrain, the Hierro v9 is a great choice for ultra-distance events or long training runs where comfort is key. There's ample cushioning to keep the legs ticking over, a breathable upper and a Vibram outsole that grips well on most surfaces.
The roomy fit makes it especially suited to swollen feet on race day, though those with narrower feet may find the midfoot a touch loose. It’s not the most agile on windy, technical trails, but if you're after a durable, road-to-trail cruiser built for the long haul, this is one of the safest options out there.
