The Sportful Sottozero winter base layer isn’t the warmest option on the market and it won’t be for everyone. If you are someone who needs warmth but also builds up a sweat when climbing, this base layer is worth checking out.
Pros
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Eight per cent wool content
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Special high-wicking panels for breathability
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Great shoulder mobility
Cons
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Very tight neck to get your head through
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Torso is longer than it needs to be
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The base layer is the piece of clothing that sets the stage for your best performance on a bike. Like a true domestique, the best cycling base layers work hard whilst almost never being noticed and rarely discussed but that doesn't mean it's any less important. They are an integral part of getting your clothing just right but despite this, they're rarely given as much thought as the outer garments like jerseys, jackets, tights or gloves.
The Sportful Sottozero is the warmest option Sportful offers if you don't need a wind block layer. This exact option hasn't yet made it to our list of the best cycling base layers, but I've been testing it to see whether it warrants inclusion.
After a few months of use, my opinion is that it represents a unique take on the genre and while it might not be perfect for everyone, there's a group of riders out there who are going to love it. If you are looking for the right winter base layer, keep reading and see if this might be the option for you.
The extra venting in the back sits below the top of the bib tights (Image credit: Josh Ross)
Design and aesthetics
When it comes to winter base layers there are those who love natural fibres and those who don't. For some people, a synthetic option will never feel quite right and it's merino for life, while others prefer the high-tech performance and ease of ownership that synthetics bring to the table. The Sportful Sottozero splits the difference. The design is that of a synthetic material but there's also a bit of wool in the mix and even though it's less than 10 per cent, you can feel its presence.
That little bit of wool is part of a bigger trend in this piece. Every manufacturer will tell you that their base layer will handle temperature regulation. After all, that's one of the more important features of a good base layer. Sportful is tackling the whole challenge a little differently though.
With the Sottozero base layer, the idea is to keep you from soaking yourself with sweat on the climb then freezing on the descent. The wool is one part of that but there are also special panels under each arm and on the lower back. These panels are sheer and you can see through them as long as there is a bit of contrast. Over that sheer backing, there is a regular pattern of small raised squares. The thicker raised sections draw in moisture and the sheer backing allows air movement.
The panels under the arms take on a diamond shape that curves through the armpit. As the diamond shape ends on the tricep it rejoins the seam travelling down the back of each arm. That means the upper part of the ventilated panel wraps onto the back of the arm in an area unlikely to be overly hot. The lower point makes more sense sitting on the side of the body below where your upper arm might cover the torso.
For the panel at the lower back, it’s covering the same area as jersey pockets occupy. On a day that’s a bit warm if you stuff extra layers into the pockets of your jersey, this section of extra ventilation works to keep you from building unwelcome heat under those layers. It’s also an area often already covered with extra insulation in bib tights.
The rest of the Sottozero design is more typical. The sleeves are long enough to cover the hands if you want them to, or pull them up and make sure you've got good mobility in the shoulders. The high (10 per cent) elastane content makes for a compressive fit that never feels loose and the neckline is high. Not high or stretchy enough to pull up over the face but the double-thick turtle neck design comes right up to the top of the neck without feeling bulky.
Venting under the arms and on the low back carries this pattern to help facilitate wicking and air movement. (Image credit: Josh Ross)
Performance
I'm a huge proponent of base layers. I always wear one and I've got a collection of different weights for different situations. The Sottozero is the warmest that Sportful makes but it's not the warmest on the market. I wore this through November and into the beginning of December then switched for most of December. As we now head into January those few degrees of warming are just enough to bring this piece back into rotation.
If you are heading out into 33F/1C weather, the Sottozero would get you through but it's not perfect. Instead, expect to use it when things warm up a little into the 40F/4C temperature range. Once you are out of the range where snow is a possibility, the Sportful Sottozero is comfortable and feels good against the skin.
You would expect that eight-per cent wool content would be imperceptible but that's not totally true. In terms of performance benefits, I do find it imperceptible but the against-the-skin feel is surprisingly close to something with much higher wool content. It feels cosy to slide on.
The neckline contributes to that cosy feeling also. It's genuinely tough to get over your head but things do settle once in place. It's high enough to protect against the zipper on any jacket. It's also warm enough to hold icy winds at bay during a ride. It's not high enough to pull up though, even in a pinch, so expect to bring a second neck warmer if you like to use them on cold rides.
The brushed interior is a low pile fleece that's very smooth (Image credit: Josh Ross)
Verdict
Doing something genuinely different in the base layer space is difficult. Sportful and a few other brands have windstopper options, there are some brands that pin their designs on merino content, and there are options for integrated neck warmers - even those with hoods. With the Sottozero base layer, Sportful looks to stand apart from the crowd by adding wool content and extra ventilation to a predominantly synthetic construction. Mostly those features aren't contributing a great deal to the actual performance (they don't hurt but they aren't adding much).
That doesn't mean the Sottozero base layer isn't worth considering though. Where Sportful succeeds in the design is in nailing a very specific temperature range that is likely to be perfect for a lot of people. It's a solid piece that covers the temperatures most people consider rideable winter weather.
Josh hails from the Pacific Northwest of the United States but would prefer riding through the desert than the rain. He will happily talk for hours about the minutiae of cycling tech but also has an understanding that most people just want things to work. He is a road cyclist at heart and doesn't care much if those roads are paved, dirt, or digital. Although he rarely races, if you ask him to ride from sunrise to sunset the answer will be yes.
Height: 5'9"
Weight: 140 lb.
Rides: Salsa Warbird, Cannondale CAAD9, Enve Melee, Look 795 Blade RS, Priority Continuum Onyx
