Mammut Alyeska Bib

Mammut Aleyaska Bibs

Size: Medium

Color: Dark Space

Shell Material: 3-layers GORE-TEX® Pro with new, optimized ePTFE membrane, durable, light, matte surface, ripstop backing

Reviewer: 6’2”, 175 lbs.

Stated Features:

• Technical freeride pants made from robust 3-layer GORE-TEX® Pro material
• Elastic insert on back of waistband for more freedom of movement when legs are extremely bent
• 2 front pockets: 1 Barryvox-compatible zip pocket with securing feature and loop inside, 1 radio-compatible zipped pocket
• Belt loops on the waistband of the pants to connect them to the jacket
• 1 map-compatible leg pocket with splash-proof YKK Vislon® zipper
• Pre-shaped knees
• Side ventilation with splash-proof zipper, with mesh backing
• Leg height can be adjusted on the inside and held in place using a press button
• Snow skirt with loop to attach ski boots
• Reinforced seam edges and ski edge protection made from Dyneema®
• Loose Fit

MSRP: $600

Days Tested: 25

Test Locations: Alaska, Maine, Vermont, & Switzerland

Mammut has been turning out core products for climbers, mountaineers and adventurers since the mid-19th century, and they’ve recently pushed into the ski and snowboard market.

As a traveling freerider, I always need a pair of lightweight pants that works (a) while splitboarding, (b) in deep pow, and (c) across a full spectrum of temperatures.

The Mammut Alyeska Bib seemed to fit the bill, so we put them to the test.

Sizing / Fit

After my last test pants from Burton [ak] felt a little big at a Large (I’m a size 32 waist), I decided to go with a Medium in the Alyeska Bib, which correlated with Mammut’s chart.

When the bibs arrived, I realized immediately that I had undersized myself according to their site, and would have to try and test these pants acknowledging that I really should be wearing a Large. This is something to consider with Mammut. They come from a technical climbing background, so everything is a tighter fit than your classic freeride outerwear from brands like Burton, North Face, or 686.

So my recommendation is to stick with what you would usually wear, and consider sizing up if you prefer a looser fit.

The Aleyaska bib is supposed to have a more loose fit than other Mammut items, but sizing myself according to their site resulted in the bibs being too tight for my comfort. The cut in the legs could have been a hair longer, however I appreciated not having to deal with my cuffs dragging in the dirt.

I did find that if I rolled the top of the bib down and wore them like a regular pant, it resolved the tightness issue, and they remained comfortable and above my hips without a belt.

The particularly tight locations included the hip width, crotch and chest of the bib. I backed the bibs down to make them as long as possible to allow more space in the hips, but even at maximum length, they still were a bit snug.

If you prefer a pant that is a bit more form fitting, these will suit you well. It is worth noting that these pants may fit two torso layers underneath while skiing. However when winter camping getting a puffy underneath wasn’t possible in my size.

Speaking of sizing, I found the bibs’ adjustment to be super smooth and minimalistic, featuring wide, stretchy straps. The only plastic is the rectangular redirect on the chest for the strap to feed through. This is an improvement over other bibs with plastic that sits on your collarbone with a pack strap on top.

The bibs feature a flexible waterproof soft shell material on the outer hips and back panel near the bib straps which adds breathability and flexibility in these key spots. In addition, the pant features a built in tight weave mesh at the very top of the cuff liner attached to the actual pant located just below the knee. Again, this is a key piece of design that adds flexibility, and like the soft shell material, puts less strain on the outer garment, meaning it fits better, lasts longer and vents better.

Waterproofing & Breathability

The Aleyaska Bib is made with Gore Pro, a fabric Blister has reviewed and discussed in detail already; see our Outerwear 201 article to learn how Gore Pro works.

This material is fully waterproof, but it does come at some cost to breathability. Mammut has down well pairing it with a lighter face fabric, which reduces weight and increases flexibility.

One area where I had some concerns was ventilation, since the Alyeska Bib only has outer leg vents with mesh, and the approximately 18-inch chest-crotch zip on the bib. So dumping heat was more of a challenge. This made these pants feel a lot less breathable. The Burton [ak] pants with Gore Pro I was testing had inner and outer leg vents without mesh which I found really helped the ventilation.

It is worth noting that I tested the Aleyaska Bibs from March – May, so I had many warm spring days at 35+ degrees (Fahrenheit). I always wear the same combo: Mon’s Royale merino boxers and long johns, and lift-accessed riding in these temperatures was fine. It was only when touring / hiking on hot days that I found these issues to surface.

On the other hand, because of their fewer zippers and intelligent material construction, there are fewer locations for water to penetrate and fewer seams to wear down over time. I never felt water soak through any part of the pant—including the cuff, butt and thighs. I fully expect these pants to have a long waterproof performance.

NEXT: Versatility, Durability, Weight, Etc.