Fatback Corvus Review: The Evolution of Fat

Not everyone will be immediately familiar with the Fatback name. In fact, just a few years ago, I would have been included in that crowd. This is likely because the Alaska-based bike manufacturer has been passionately focusing on just one thing since 2007: fat bikes. Although Fatback won’t take responsibility for inventing the fat bike, they’re certainly confident in saying they “reinvented it.” From the introduction of the 170mm symmetrical hub in 2008 to the new industry standard 190 and 197mm rear hubs for 5” tire clearance, Fatback has played a huge role in the progression of comfortable and efficient fat bikes.

• Highlights
• Frame: Carbon
• Seatpost: 31.6mm
• Bottom Bracket: Threaded 100
• Hub specs: 197x12mm (rear); 150x15mm (front)
• Max tire: 26×5″ / 29×3″
• Weight: 28.4lbs/12.9kg (Large with Fyxation pedals)
• Price: $3,499 (GX1 Eagle)

The Fatback Corvus has created quite a name for itself in the world of adventure-ready fat bikes since its initial release four years ago. Back in 2016, Fatback gave the Corvus a face lift by adding Anything Cage mounts on the fork, more tire clearance, a slacker front end, and shorter chainstays. As Fatback puts it, “The Corvus represents 10 years of fat bike development, culminating in the most refined carbon fat bike available anywhere.” It’s a bold claim, so we decided it would be a good idea to ride one for ourselves.

The current Corvus is offered in six different builds: SLX, XT, GX1, XO1, GX1 Eagle, and XO1 Eagle, which should accommodate any rider preferences out there. A carbon frame and fork offer generous clearance for the stock Schwalbe Jumbo Jim 4.8” Lite Skins mounted on Alexrims Blizzerk SL 90s. We got our hands on the GX1 Eagle build, delivered with upgraded Terrene Cake Eater 4.6” Lights for some fun in the snow, dirt, and all those less-than-desirable conditions in between.

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Unlike many other carbon bikes we’ve reviewed, Fatback has obviously been paying close attention to what features are valued in an expedition-friendly bike designed for speed. Their fat bikes are often seen at winter ultras like the Iditarod Trail Invitational in Alaska, and have proven to be quite capable more than a few times. To start, Fatback added rear facing Anything Cage mounts on the fork, two bottle mounts in the main triangle, and an additional mount under the downtube. It’s also great to see a huge front triangle, which swallowed up my large Porcelain Rocket 52hz frame bag in the best possible way, a key ingredient that’s often sacrificed in the name of preserving standover height. And, last but not least, a threaded bottom bracket. Pressfit skeptics, rejoice!

Fat Bike Geometry

Undoubtedly, any bike that was designed for riding on snow is going to feel markedly different than your average trail bike. It’s not just a matter of slapping on some big tires and calling it a day, especially when the goal is to make a fat tire bike fast. One concern is having proper weight distribution in soft terrain. While it’s fun to quickly float over some snow or sand after tossing all of your weight over the back end of the bike, this doesn’t really work if there is no hard packed salvation on the other side. Weighting the front tire, while not losing traction on the rear, is accomplished with shortened (but not overly shortened) chainstays and a steep headtube angle. The result is a fairly aggressive, but stable, position.

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To be honest, the first time I got on the Corvus I was taken off guard by the position it put me in. I was pushed further over the front axle than I imagined I’d be, and the result was slightly twitchy steering that took some getting used to. However, on snow and in unpredictable terrain, the Corvus rode straight, climbed smoothly, and responded much better to a light touch. Riders will often describe fat bike handling as “self-steering” due to the larger width tires and lower tire pressure, which can feeling like tugging or grabbing when moving at slower speeds. This feeling still exists, but significantly less so at higher speeds or while descending with weight over the rear end.

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To offer a comparison, the Fatback Corvus and Salsa Mukluk share more than a few similarities when it comes to geometry, build options, and price point. Both sport an updated, slightly more aggressive geometry, notably a 69° head tube angle and 73° seat tube angle. Both bikes keep the rider’s weight low, centered, and stable, but the Mukluk offers a shorter chainstay length, at 440mm or shorter (depending on the frame size), compared to the Corvus at 455mm. This also relates to the longer wheelbase of the Corvus, which helps create a solid platform when navigating loose and uneven terrain.

Both Salsa and Fatback offer GX1 Eagle builds for $3,499, as well as higher end XO1 Eagle and lower end SLX. It would have been nice to see a cheaper build from Fatback, ideally in the sub $3K category, although their prices are right on par with similar carbon fat bike offerings. Salsa managed this with the Mukluk, rolling out a non-carbon NX1 version that’s still a great bike but is a little easier on the wallet. In the end, you get what you pay for, and Fatback is clearly catering towards the high-end crowd.

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Make Fat Fast Again

Fat and fast aren’t words that are paired very often when it comes to bikes. Fat bikes are satisfyingly stable, making them a fantastic option for bikepacking in remote areas when the terrain is unpredictable, and they handle being loaded with gear well. Besides the aggressive geometry of the Corvus, there are several other features that contribute to its ability to roll quickly and confidently in pretty much any conditions.

A heavy fat bike feels like a heavy fat bike, and there’s just no way of getting around that. Swapping larger wheels onto a carbon frame takes the advantages of the fat bike and opens up the possibilities of riding further, faster, and struggling less when it comes time to lift it over or up something. Even with 26 x 4.6” tires, the lighter and more aggressive design of the Corvus encourages speed, and it’s a weird feeling when considering what’s going on under you.

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The Corvus I rode came with Terrene Cake Eater Lites, which aren’t the most aggressive fat tire out there, but offer a low and narrow centre tread designed to keep up speed when you want it. It actually felt considerably quicker on hard surfaces than the 27.5+ Surly Dirt Wizards that are on my Karate Monkey right now, which is often how I make my comparisons when it comes to speed. The stock 4.8” Jumbo Jim Lite Skins share the similar lightweight qualities of the Terrenes, but the centre tread won’t be as fast rolling—something to consider when checking out Fatback’s stock builds. On the other hand, the Cake Eater’s lower tread height isn’t as desirable for venturing off hard packed snow as the Jumbo Jim’s larger and more spaced tread. Thankfully, the Cake Eater’s are studdable if some extra traction is needed, while the stock Jumbo Jims are not.

I found the SRAM GX1 Eagle drivetrain to be a great complement to the whole package. Whether I was punching up groomed singletrack or slogging up the steep, rutted, and snow covered forest service roads, I was always able to keep a manageable cadence on the way up, and maintain my speed on the way down and into the flats.

Fatback Corvus GX1 Eagle Build

As mentioned earlier, it’s not often you see so many different stock build options for the same frame. Fatback covers the 11-speed options with Shimano SLX or XT, plus Sram GX1 or XO1, and also offers 12-speed XO1 and GX1 Eagle configurations. Amongst these different builds, you’ll also see changes in cranks, brakes, and the Shimano SLX and SRAM GX1 models sport alloy seatposts and handlebars. There are a few other component changes between the lineup, but each model is worth its value, and they all correlate with their respective price tag.

It’s also worth mentioning that the Blizzerk SL90 rims came taped, ready for tubeless, and although the rear rim tape job seemed to be damaged in shipment, the front setup has held firm and true for over three months now. Depending on the conditions, I ran my pressure around 7-15 PSI, and the huge volume of the tires meant fantastic traction and a noticeable amount of cushion when cruising through chunky sections.

Like most modern fat bikes, the Corvus has the ability to run both 27.5+ and 29+ wheels when the extra flotation and grip of true fat tires aren’t needed. Fatback recommends maintaining a rigid front end when using 29+ wheels, but notes that running front suspension with 27.5+ can work as well. With a 60mm bottom bracket drop, it seems like it would possible with either 27.5+ or 29+, but it may be a bit more fitting for 29 x 3.0″ tires that have a diameter more similar to the Corvus’ intended tire diameter. I think a lightweight 29” wheelset on the Corvus would be a fantastic setup for summertime endurance rides and races, but testing that configuration wasn’t in the cards for me this time. If any Corvus owners out there have run different sized wheels, we would love to hear about it in the comments below.

Frameset

• Frame Corvus Carbon
• Fork Corvus Carbon
• Color Black / Green

Drivetrain

• Front Der n/a
• Rear Der SRAM GX1 Eagle
• Cassette SRAM GX-1275 10-50t
• Chain SRAM GX Eagle
• Crankset SRAM GX Eagle 30t
• Shifter SRAM GX1 Eagle 1x
• Brakes & Rotors SRAM Guide R Hydraulic Disc 180/160

Components

• Headset Fatback
• Stem Fatback TS1
• Handlebar Fatback TG1 Carbon
• Grips Ergon GA30
• Seatpost Fatback Carbon, 31.6 
• Saddle Fatback Saddle CnR-Titanium

Wheels

• Front Wheel Alexrims Blizzerk SL90, Thru-Axle, 15 x 150mm
• Rear Wheel Alexrims Blizzerk SL90, Thru-Axle, 12 x 197mm 
• Tires Terrene Cake Eater Lite 26×4.6”, Folding / Tubeless Ready

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I was most interested in the GX1 Eagle build for a few reasons. First, I’ve wanted to get my hands on the more affordable 1×12 Eagle drivetrain for a while now, as I’ve been running Shimano and SRAM 1×11 for the past few years. Secondly, I think those interested in purchasing a fat bike of this calibre are going to give the option to run 1×12 some good thought, as the increased range definitely makes sense for a bike like this. When it comes down to the ride and feel of the Corvus, even the cheapest GX 1×11 build will perform great, and some may even prefer it. If you’re not interested in a complete build, Fatback also offers the Corvus as a frameset with their rigid carbon fork included for $2,200.

As expected, the GX Eagle drivetrain was snappy, shifted consistently and accurately, and required only minor adjustments to accommodate for cable stretch. I had no issues, and wouldn’t anticipate any arising, considering the pricetag associated with high-end drivetrains like this. I was happy riding in snow, gravel, and dirt singletrack with the 30t chainring and 10-50 GX cassette. When loaded up with gear, it was always a pleasant surprise to shift up into the huge 50t cog, making things a little easier on my young little knees. With a 30t ring up front and the smallest 10t in the back I was able to keep the pedals spinning on most non-technical descents and into the flats as well.

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For once, we can also say that the bottom bracket choice won’t deter those on the hunt for an expedition-ready carbon fat bike. Rarely do we encounter any issues with press-fit bottom brackets, but on longer, international bikepacking expeditions, the simplicity and serviceability of a threaded bottom bracket has its appeal. And, some folks simply don’t like the idea, or the squeaking that sometimes ensues from a press fit.

• Model Tested Fatback Corvus GX1 Eagle
• Weight 28.4LBS/12.9KG (LARGE WITH FYXATION PEDALS)
• Place of Manufacture Taiwan
• Price $3,499
• Manufacturer’s Details FatbackBikes.com

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