La Sportiva updated their popular line of Nepal mountaineering boots with the new Cube GTX. The Cube is an incredibly lightweight, single layer, technical winter boot that's ideal for mixed terrain. We put it to the test in the country of its namesake while climbing in the Himalayas.
What Are They Supposed to Do? Previous versions of the Nepal offered amazing warmth and superb technical performance on all types of climbing terrain while remaining lightweight. The 879g Nepal Cube GTX ($US575) is designed to offer similar performance, but is a full113glighter than the EVO GTX. Additionally, the Cube's insole and midsole are a combined 12mm thinner than the EVO's — creating a lower profile for added stability.
Many of the EVO's existing construction materials and features have been carried over to the Cube including the use of a 3.2mm thick silicone-impregnated leather upper, resolabe Vibram soles with an Impact Brake System (which slants the sole lugs in opposing directions to provide traction both forwards and back) and a GoreTex insulated liner. The Cube also uses a hinged ankle to prevent lateral torsion and has a removable, adjustable tongue for a custom fit. These features combined make the Cube GTX one of the most technically-advanced mountaineering boots on the market.
Fittingly, I tested the Nepal Cube GTX in Nepal.
How're They Supposed To Do It? The Cube uses a 4mm thick carbon fibre honeycomb insulated insole. The honeycomb design allows the insole to be incredibly lightweight and thin while providing adequate insulation and rigidity for climbing cold, rough terrain. Additionally, the crampon-ready polyurethane midsole is only 2mm thick. For contrast, both the EVO's insole and midsole are 9mm thick. Thinner soles allow climbers to have more stability by lowering their centre of gravity, putting them more in-touch with the ground, with or without crampons.
The Cube is nearly 15% lighter than the EVO; that weight savings was achieved through the improved insole. Lighter boots improve the climber's performance both during approach (less weight in the pack) and while climbing (lighter feet equals less energy exerted with every step).
The silicone-impregnated leather supplied by Perwanger of Italy. They tan the leather with a special process that makes it extremely water-repellent, while still remaining breathable. It's the most durable leather available; made from the corium, which is the strongest part of the leather.
The ankle utilises a hinge system that allows lateral flexibility while still allowing longitudinal lockout for excellent support and safety.
Air-injected rubber rands protect the Cube's leather from cuts, gashes and abrasion.
How Does It Perform? I put the Nepal Cube GTX to the test all over the world in all kinds of climbing conditions. First, on an end-of-season climb of Mt. Baker in the North Cascades. That climb was cold, wet, and featured mixed terrain. Then I tested them in Iceland, again in cold, wet conditions with fresh snowfall and lots of glacier travel. Finally, I brought them to the country of their namesake for an end-of-season climb of the 6189m Imja Tse — more popularly known as Island Peak. Though that climb was only one day long and dry, it was cold and high.
The first thing worth noting about the Cubes is their low weight for a winter boot. My "approach hike" to Island Peak was more than 160km long. In addition to climbing gear and clothes, I was carrying computer and camera equipment. All of that added up to about 60 pounds and I shaved weight wherever I could. The Cubes are about a pound lighter than my La Sportiva Spantiks and they still did the trick for a short, but high-altitude climb.
The resolable Vibram soles feature the unique Impact Brake System, which is said to increase braking power and reduce impact forces.
Wearing the Cubes is like wearing a pair of very supportive (but very warm) hiking boots. They do not feel heavy or clunky; this is arguably due to their low weight (heavy duty hiking boots can often weigh up to 850g) and thinner soles, which noticeably improve contact with the ground. When we finished glacier travel and started hiking down from Island Peak, everyone switched out of their heavy double boots into hiking boots; I was able to leave the Cubes on without any exertion penalties. While the boots are light — they still provide massive support. When climbing rock, I was able to step up using only my toes without worrying about slippage caused from boot flex. Yet even with their rigidity, the Cubes remained comfortable for hiking.
Mt Baker, the snowiest mountain the world, is known for its cold wet conditions; my experience was no different. Our entire climb was through wet snow; the Cubes did not wet out, yet they vented well — keeping my feet dry the entire day. While climbing down from a volcano in Iceland, we got caught on an outlet glacier during a torrential, all-day-long downpour. The boots eventually did wet out, but mountain boots are not designed to endure the type of rain that we experienced. Though they wet out, my feet stayed warm in the near-freezing temperatures.
Almost every guide to climbing Island Peak that I read suggested that climbers wear plastic double boots. Since it was only a one day climb and there would be no need to dry out my liners overnight, I figured that I could get away with the Nepal Cubes. Once on the glacier, I saw that I wasn't alone: at least half of the other climbers that I saw were wearing some version of the Nepal, whether it was the EVOs, the Extremes, or the Cubes.
The key to warmth with boots (and gloves) is proper circulation. If your boots are too tight, blood circulation throughout your feet and toes will be limited and you will be cold. With that in mind, I wear thin wool socks with my mountain boots (insulation should come from the boots themselves; not necessarily your socks) so that I have plenty of wiggle room for my toes.
I wore the Cubes to the summit of Imja Tse, a 20,305' Himalayan peak. I used them with the CAMP XLC 490 ($US150) aluminium crampons for one of the lightest high-altitude setups you can wear.
I'm not sure what the temperatures were on Island Peak the day that I climbed, but at 20,000' it was cold. The snow we were climbing on was very compacted and more closely resembled ice, so our boots were always on the surface. Despite that and my good circulation, my toes felt frozen. At times, I wasn't entirely sure if they were still there, but fortunately I had adequate room in the toe box so I made a conscious effort to keep wiggling them — even if I couldn't feel them wiggle. Once we got off the ice and made it down to a lower elevation, the feeling eventually came back. Back at base camp, I was relieved to see that I still had all of my toenails. On Mt. Baker, my toes got cold at times, but I never lost feeling. I've heard that the Cubes are warmer than the EVO's, but not as warm as the Extremes.
The Cubes fit really well and were comfortable to wear. I never got hot spots or blisters from wearing them (but to be honest, I never get hot spots or blisters from any shoes or boots). The removable, adjustable tongue does a good job of customising the fit. There's a locking D-ring at the joint, allowing you to lace the lower and upper parts with varying degrees of tightness.
The Cube's heel and toe welts are both very sturdy and accept automatic crampons with ease and security. Strap on crampons also fit very snugly around the boots.
All of these features and performance come at a cost. At $US575, the Nepal Cube GTX is one of the most expensive single layer mountaineering boots on the market. Take it how you will, but when my life is on the line, I want the best.
Adventure Ready? Absolutely. The Nepal Cube GTX improves on an already great design by decreasing weight and utilising a thinner sole for greater stability. If you already own a pair of EVOs, it's probably not worth upgrading. However, if you're on the market for a new pair of single layer mountaineering boots, the Nepal Cube GTXs are definitely worth considering. They are $US65 more expensive than the older EVOs, but the improvements justify that premium.
Pictures: Chris Brinlee Jr