Likely one of the most important choices a climber makes involves their footwear. Happy feet are so crucial for happy climbing and my feet have been quite happy this season while I’ve been testing the Arc’Teryx Acrux AR Mountaineering Boots. Before I break into the details here is how they have been tested:
Mountaineering: (paired with Petzl Vasak Leverlock crampons)
4 winter ascents of Mount Washington with the lowest ambient air temperature around -20f and wind-chills around -50f.
30+ pitches of waterfall ice climbing including Black Pudding Gully (WI4+), The Black Dike (WI4+) Drool of the Beast (WI5-) and Repentance (WI5).
The author on Drool of the Beast, photo by Brent Doscher Photography
I mention specifically what crampons I tested these with as this is a very important consideration when selecting a climbing boot, especially in this case and I will get into that further in the review. But first lets take a look at some of the details of this design.
I’ll start with some preliminary info from when I first received these boots back in October.
“A pinnacle of design for mountaineering, ice and mixed climbing, the Acrux AR is the lightest, most durable, and lowest profile insulated double boot available.”- Arcteryx.com
That is a strong statement, and it happens to be true. Let’s compare some of the other lightweight double boots on the market:
La Sportiva Spantik (88.96 oz/pair)
La Sportiva Baruntse (82.96 oz/pair)
La Sportiva G2 SM (72.22 oz/pair)
Scarpa Phantom 6000 (70 oz/pair)
Arc’teryx Acrux AR (69.1 oz/pair)
The obvious difference between these and my Batura’s is that these have a removable liner.
These liners “feel high-tech” in hand. I wore them around the house and they feel like a comfy slipper designed for astronauts. From arcteryx.com:
“Arc’teryx Adaptive Fit technology uses a removable bootie that employs stretch textiles and minimal seams to create an instant custom fit with no pressure. With protection extended beyond the cuff of the boot and the highest level of breathability in this category, the bootie’s GORE-TEX® membrane optimizes climate control and waterproof benefit. The perforated PE foam’s quick dry properties improve comfort, and a rubberized sole allows the bootie to be used as a camp shoe.”
Arc’teryx partnered with Vibram® and created the AR outsole using Vibram® Mont rubber which keeps its frictional properties in sub-zero temps.
“The specially developed Vibram® AR outsole is designed for support and sure footedness. The tread and construction feature a semi-blocked toe, with anti-slip grooves, a medial climbing support zone, and heel created to provide braking on steep descents. The Vibram® Mont rubber compound maintains its performance in sub-zero conditions.”
Now that I have had sufficient time in the field to test them let’s get into the question on everyone’s mind. How do these perform?
On the approach
Honestly these have been the most comfortable mountaineering boots I have yet to wear. They feel like they were custom made for my feet. For reference I am a US men’s size 9, EUR 42, medium width forefoot with a slight Morton’s toe. Unlike my previous double boots (Koflach Degre, Vertical, and Arctis Expe) it is easier to put this boot on by first putting the slim fitting liner on then sliding into the outer boot. When the liner is already in the boot it is a little more tricky to slide on but not impossible.
The lacing system is probably the only thing I could imagine being improved upon. There is no traction/tension grabber that is becoming common in a lot of boots in this category. For a boot at the high end of the category I would LOVE to see Arcteryx take it a step further and add a ratcheting lacing system like Boa.
As it stands I’ve adapted my lacing strategy. For general mountaineering and easy ice climbing I lace them at home and leave them all day. For harder ice climbing (WI4 and up) I’ll lace them at home, approach, then take the time at the base of the route to snug them up for better performance on the vertical. It doesn’t take long and leaving them loosely laced on steep ice can lead to some insecurity.
For comfort on the approach and descent these score very high. They are super light and warm enough for my feet in all the conditions I’ve tested them in. I do have “warm” feet though so if you suffer from cold feet I would suggest some solid test runs before going to significant altitude. The long term comfort is so significant that I’ve returned home after 14 hour days and left them on while stocking the wood stove and cooking dinner. No joke I have not felt the need to pull my feet out of these as soon as I get home even after significant slogs.
One of the reasons they might be so comfortable on the approach and descent is the small amount of flexibility within the shank/out-sole, a trait some who have tried them are concerned about, but one that I feel is easily remedied. I will elaborate more on that in the next section.
On the climb
The slim looking low profile Arc’Teryx Acrux AR Mountaineering Boots are the Lamborghini of the climbing boot world. Ok, that might be going a bit overboard but seriously I find these perform extremely well on steep water ice when paired with the right crampon. Why is the crampon pairing so important? Two reasons.
- These are super light boots. For hard ice climbs a heavier crampon might actually reduce your energy expenditure by giving your boot/crampon a better balance for efficient kicks. Before you call me crazy consider this is the same theory that explains the practice of adding pick weights to your ice axes. I find the heavier Black Diamond Cyborgs and CAMP Cassin Blade Runners to add a nice amount of weight allowing me to “kick lighter” and let the boot/crampon do the work. So super light boots are a plus for the approach and descent, but it’s nice to add a little mass for the kicking portion of your climb!
- These boots have some flex. That small amount of forefoot flex feels great on that 8 mile approach, but when you are front-pointing on near vertical ice having a secure platform takes precedence. I noticed the flex first when leading a 3+ route wearing my well worn Petzl Vasak Crampons. It wasn’t a big deal, but it was noticeable. I’ve since lead multiple grade 5 ice routes using the Black Diamond Cyborgs and CAMP Cassin Blade Runners and in all cases the inclusion of the stiff heavier crampon virtually eliminated all noticeable flexibility while front-pointing on both steep rock and ice.
Five months of some of the best Northeastern ice climbing I’ve had in years have left me with a super positive impression of the Arc’Teryx Acrux AR Mountaineering Boots. Slipper like comfort, 3-season like weight (yet still plenty warm for my feet), and high end performance when it matters most all add up to a fantastic new edition to the growing assortment of lightweight double boots. You should try a pair on!
Thanks for reading! Take it one step further and comment below! Have you tried them? What did you think? What’s your current boot crampon/setup?
Disclaimer: Arc’Teyrx provided a pair of these boots for the purposes of review but all opinions expressed above are my own. Affiliate links help support this blog.