A fat bike is about opportunity. An opportunity that opens up the seasons, and opens up the terrain. You can go places where you’d never consider before owning one. Fat bikes’ wider-than-normal wheels provide extra grip, making them ideal for riding in snow or through deep mud, so perfect for riding in winter. The tyres, which are designed to be run at really low pressures, spread the load and add a bit of suspension to what is otherwise a rigid frame too.

People who mock fat bikes for their motocross-style looks are usually people who haven’t tried them. Get one of these on a skiddy, wet trail or a snowy slope or the kind you’d never ride on your regular whip and it’s guaranteed to a put a grin on your face.

The full-carbon Sonder Vir Fortis fat bike, made by Alpkit, is basically the perfect bike for a winter bikepacking trip. Like all the bikes Alpkit sell (which they market under the Sonder brand) these can be built to order with fully customizable kit: different stem length, saddle, wheelset, gear ratio – it’s all up for grabs.

“Fat bikes' wider-than-normal tyres provide extra grip, making them ideal for riding in snow or through deep mud."

alpkit-sonder-vir-fortis-fat-bike-review-2016-2017-best-carbon-frame-fat-bikes-for-winter-mountain-biking-cycling-bikepacking-gear-3

alpkit-sonder-vir-fortis-fat-bike-review-2016-2017-best-carbon-frame-fat-bikes-for-winter-mountain-biking-cycling-bikepacking-gear-3

alpkit-sonder-vir-fortis-fat-bike-review-2016-2017-best-carbon-frame-fat-bikes-for-winter-mountain-biking-cycling-bikepacking-gear-6

alpkit-sonder-vir-fortis-fat-bike-review-2016-2017-best-carbon-frame-fat-bikes-for-winter-mountain-biking-cycling-bikepacking-gear-6

alpkit-sonder-vir-fortis-fat-bike-review-2016-2017-best-carbon-frame-fat-bikes-for-winter-mountain-biking-cycling-bikepacking-gear-8

alpkit-sonder-vir-fortis-fat-bike-review-2016-2017-best-carbon-frame-fat-bikes-for-winter-mountain-biking-cycling-bikepacking-gear-8

alpkit-sonder-vir-fortis-fat-bike-review-2016-2017-best-carbon-frame-fat-bikes-for-winter-mountain-biking-cycling-bikepacking-gear-11

alpkit-sonder-vir-fortis-fat-bike-review-2016-2017-best-carbon-frame-fat-bikes-for-winter-mountain-biking-cycling-bikepacking-gear-11

This head-turning model is made from high grade T700 carbon – including the fork – and is ridiculously light - the frame itself weighs just 1380g. This makes it perfect for the kind of climbing that will inevitably be involved in any winter bikepacking mission.

There are neat little touches to the Vir Fortis frame such as the internally-routed cables which are trickier to snag. This also makes attaching Alpkit’s custom-built frame bags less of a faff. The geometry of the frame isn’t too aggressive, so it’s great for climbing on, but the 68.5 degree head angle is slack enough to handle most descents with ease.

If you opt to buy the standard build kit rather than the frame only, Alpkit ship it with a SRAM GX1 groupset, featuring a 1x11 gear configuration that’s really versatile - the super-wide 10-42t gear range on the cassette means there’s a gear for every gradient.

alpkit-sonder-vir-fortis-fat-bike-review-2016-2017-best-carbon-frame-fat-bikes-for-winter-mountain-biking-cycling-bikepacking-gear

alpkit-sonder-vir-fortis-fat-bike-review-2016-2017-best-carbon-frame-fat-bikes-for-winter-mountain-biking-cycling-bikepacking-gear

alpkit-sonder-vir-fortis-fat-bike-review-2016-2017-best-carbon-frame-fat-bikes-for-winter-mountain-biking-cycling-bikepacking-gear-5

alpkit-sonder-vir-fortis-fat-bike-review-2016-2017-best-carbon-frame-fat-bikes-for-winter-mountain-biking-cycling-bikepacking-gear-5

alpkit-sonder-vir-fortis-fat-bike-review-2016-2017-best-carbon-frame-fat-bikes-for-winter-mountain-biking-cycling-bikepacking-gear-13

alpkit-sonder-vir-fortis-fat-bike-review-2016-2017-best-carbon-frame-fat-bikes-for-winter-mountain-biking-cycling-bikepacking-gear-13

And those tyres – wow. The build kit bike comes with Schwalbe Jumbo Jim 4.0 Liteskin Tyres with an aggressive pattern. These suckers can take anything, but excel in snow, mud and sand. The bike could also take tyres up to a frankly ludicrous 4.80 inches, in case you feel the need to go bigger.

Another advantage to buying a bike directly from Alpkit (as well as the price) is that many of the bikepacking add-ons, such as the Stingray frame pack can be custom made for a bike they know intimately.

If you’re thinking of going bikepacking in winter, this is the whip for you.

Alpkit Sonder Vir Fortis Fat Bike Stats:

The 100 Best Outdoor Products for Winter 2016 View them all

Shot on location in Chamonix.