The lightweight Salomon Tundra Boot, insulated with Aerogel, is comfort rated to -40 F. Men's boot on left; women's on right.
The Salomon Tundra Mid WP insulated boot probably has the highest warmth to weight ratio to be found anywhere. It's insulated with Aerogel, which was developed by Aspen Aerogels for NASA, and is claimed to have the highest thermal insulation value of any solid material available. Aerogel is a silicon-based solid with a porous, sponge-like structure in which 99.8% of the volume is empty space. It's one thousand times less dense than glass, which is another silicon-based solid. Aerogel is not like conventional foams, but is a special porous material with extreme microporosity on a micron scale. The individual pores are only a few nanometers in size. A nanometer is one billionth of a meter.
A disc of Aerogel (left) feels weightless. Aspen Aerogels incorporates Aerogel into a fabric called "Spaceloft" (center) for use in footwear and garments. In the Tundra, the Spaceloft fabric surrounds the toebox and the sides of the foot; areas that are most vulnerable to getting cold. The chart (right) shows that Aerogel's insulation value/inch (clo) is about three times that of other synthetic insulations.
This boot was initially introduced in fall 2007 as the Aspen, which was significantly taller (11 inches in back, 12 inches at the side). The Aspen was replaced by the Tundra in fall 2008, and the new boot measures 9.5 inches at the back and 10 inches at the side. In short, the Tundra gets it right (read my comments in the following section).
The overly tall Aspen boot (left) was replaced by the Tundra (right) one year later.
The Tundra is nicely designed, and is constructed of very durable materials (see specifications table). The uppers are all synthetic, with a very durable molded rubber/fabric (like Hypalon) lower section cemented to the outsole. Both the toe and heel have rugged bumpers for extra durability, and the heel has a notch for snowshoe and crampon straps. The grippy outsole has Contragrip rubber which remains flexible in extreme cold temperatures.
I tested the Aspen and Tundra on several day trips while snowshoeing and ice fishing, and on four multi-day winter snowshoeing trips where I camped in an igloo (two trips) or a tent (two trips).
My first reaction to the Aspen was that it was way too tall! When I laced the boots all the way up and snowshoed in them, my ankles were very tired at the end of the day. They were like walking in downhill ski boots! The solution I found was to lace them only part-way so my ankles were more free to bend. Salomon apparently recognized the problem early-on, because they replaced the Aspen with the shorter Tundra one year later. By the numbers, the Tundra isn't that much shorter (9.5 inches in back versus 11 inches), but it does, in fact, get it right. I am very satisfied with the height of the Tundra in terms of ankle support and flexibility. Although Salomon calls the Tundra a mid-height boot, it is clearly a full-height boot in my opinion.
Although the Tundra is no featherweight, it is remarkably light for an ultra-warm boot. The measured weight of the Tundra in men's size 12 is 26.8 ounces/boot. To put that into perspective, the popular Keen Growler (insulated with 200 gram KeenDry) weighs 22.5 ounces/boot in size 12, and Baffin Outback (a lightweight pac-type boot with a removable liner) weighs 34 ounces/boot in the same size.
I tested the Tundra while snowshoeing, winter camping, and ice fishing. Note the boot's durable upper, rubber toe and heel bumpers, notch to hold a snowshoe (or crampon) heel strap, and snug fit around my leg.
I found the Tundra's fit to be slightly on the snug side. A size 12 normally gives me ample room for two pairs of socks, but I found room for only one pair of heavy wool socks without being too tight. I suggest sizing up one size above your hiking shoe size. The width is adequate for my wide feet, but they are not super wide.
The Tundra is especially suited for snow travel. The uppers are made of durable materials, with a tough toe bumper and molded rubber/fabric (like Hypalon), with no exposed seams, in the lower section to resist abrasion in crusty snow. I also like the snug closure of the gusseted tongue and furry collar around my leg to seal the top of the boot. They lace up quickly with one yank on the laces. Curiously, the laces are extra long, so rather than contend with loose laces, I wrap them around the top of the boot and knot them, as shown in the photo above.
The Tundra's Contragrip outsole has an aggressive tread and the rubber remains flexible in extreme cold.
For sheer warmth, the Tundra is delightful, especially on day trips in really cold weather. Although it is true that Aerogel provides a lot of warmth with minimal bulk and weight, the -40 F temperature rating of the Tundra an approximate and optimistic claim (as is the case for most insulated boots). Their actual warmth depends on the weather and the user's activity level, fitness, metabolism, foot perspiration, circulation, exposure time, clothing, and sensitivity to cold.
The Tundra is definitely waterproof; I did not have any leakage at all during my testing. However, I did have some moisture buildup inside the boots from sweat, which can compromise their warmth. It was not an issue on day trips in cold temperatures, as long as I kept moving, but it was problematic on multi-day snow camping trips. On one -11 F morning it took several hours for my feet to warm up. I weighed the boots and my socks on several occasions when my feet became chilly, and found that it took only a few tenths of an ounce of moisture to cause cold feet. I found that I could minimize the problem, and keep my feet warm, by changing my socks frequently and drying them in my sleeping bag. But it's very difficult to avoid moisture buildup in a boot with a membrane. Although pac-type boots are heavier, their removable liners are a distinct advantage because you can dry them out in a sleeping bag overnight.
Overall, the Tundra is remarkably rugged, lightweight, comfortable, and warm, and deserves our highest rating for day trips. The moisture buildup issue on multi-day trips depends a lot on the hiker, temperatures, activity level, how much his/her feet sweat, and how much they manage moisture by changing socks.
|Salomon Sports (http:// http://www.salomonsports.com/)|
|2008 Tundra Boot|
|Aerogel incorporated into "Spaceloft" fabric|
|Upper is water-resistant fabric, synthetic leather, and molded rubber/fabric (like Hypalon), midsole is molded EVA, traction rubber outsole|
|Winter Contragrip outsole, proprietary waterproof-breathable membrane, molded EVA midsole, gusseted padded tongue, polyester fleece lining, furry top closure, rubber toe cap, rubber heel cap with molded notch for snowshoe or crampon strap, external heel counter, self-locking eyelets|
|Measured weight men's 12 26.8 oz/boot (760 g), manufacturer specification 24 oz (681 g) for men's 9|