Specialized Fatboy Expert Carbon review

Lean and mean race-ready fat bike

BikeRadar score4/5

Winter fat bike racing has gained a firm foothold in the snowpacked portions of the United States, with many ski resorts and recreation areas developing groomed tracks and allowing fat bikers to intermingle with Nordic skiers on existing cross-country ski trails.

The Specialized Fatboy Expert Carbon leans more toward this track, as opposed to the expedition-ready fat bikes offered by companies such as Surly. The particular Fatboy comes race-ready with a lightweight carbon frame, fork and wheelset. This trifecta of composite parts keep the weight down to just 23.2lb / 10.5kg.

(NB: The Fatboy Carbon Comp is unavailable in the UK at time of writing; however the cheaper Comp Carbon and top-end S-Works models can be purchased.)

Sleek carbon lines

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The Fatboy Expert Carbon sits just below the S-Works model in kit and price

It’s somewhat surprising that Specialized, a company based in sunny and temperate California, decided to dive straight into the deep end of the fat bike pool by offering a wider variety of fat-tyred fun machines than anyone else. The Fatboy comes in versions with 20 and 24in wheels for kids and there’s even a women’s–specific fat bike line called the Helga. There are eight models in the adult/unisex Fatboy line, including three carbon bikes.

The Fatboy Carbon Expert is the mid-priced carbon offering. The carbon frame features sleek internal routing for the rear brake and shift lines. The front brake similarly routed through the left carbon fork leg. The rigid Chisel fork is suspension corrected for a RockShox Bluto and uses the same 150x15mm thru-axle system, making it an easy swap if you need extra cushioning. 

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The Fact carbon frame sports a 197mm thru-axle rear 

The Fatboy uses the wider 197x12mm thru-axle rear end and a 100mm-wide Press-Fit 30 bottom bracket. Long, narrow chainstays allow the Fatboy to accept 5in-wide tyres. A few words on the front and rear axles: Specialized opted to use the Syntace X-12 thru-axle system, which sits flush with the frame, but requires a 5mm hex key to install or remove the wheels. In my experience, this is a good thing, as fat bikes are wide enough without having to take into account Maxles or similar lever systems dangling out in harms way. (And you should always have a multi-tool at the ready anyway, right?)

Lightweight kit with lots to like

Fat bikes don’t have to be overweight lumbering beasts; it just takes a little bit of carbon (and a lot of cash) to get the gram count on par with a standard hardtail.

The Fatboy Expert Carbon comes with a smart selection of components. The drivetrain consists of the stiff and light Race Face Next SL crankset paired with SRAM’s X01 shifter and derailleur with an X1 cassette.

SRAM’s budget-minded Guide R brakes may lack the contact point adjustment of the RSC model, but their performance is equivalent. I’ve ridden the Guide series of brakes on several fat bikes this season and their cold-weather performance continues to impress me.

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SRAM's Guide R bikes may be affordable, but they're far from low-end

The Fatboy’s cockpit is made up of Specialized’s own alloy handlebar and stem along with the comfy Henge saddle, which rests on a Race Face Next SL carbon seatpost. 

The stars of the Fatboy’s component kit are HED’s Big Deal carbon rims. These single-walled carbon rims have an internal width of 80mm and weigh just 445g each. Add in tubeless compatibility and you have a winning recipe for minimising rotating weight. Speaking of tubeless, Specialized's own tubeless-ready 26x4in Ground Control tyres round out the build.

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The Ground Control tires are fast-rolling and easy to set up tubeless

Swift and steady

As mentioned in the introduction, the Fatboy Expert Carbon is race-ready, right out of the box. That is, with the caveat that the stock build is best suited to groomed snowpack. The fast rolling, 4in-wide Ground Control tyres lack the float of 5in treads in unpacked snow, though the supple 120tpi casings do a commendable job of maximising grip.  

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The stock 28t chainring with the 10-42t cassette was a good match for winter riding

After riding and racing the Fatboy, I would describe its demeanor as swift but steady. The 70.5 degree head tube angle and the 750mm wide handlebar make it easy to keep the big wheels in check when up to speed. The long, 17.9in / 455mm chainstays don’t reward subtle course adjustments to the same degree as shorter rears, but they give the rider a bit of fudge-factor when sliding the back end through slick corners.

While the bike’s handling was steady, its acceleration was excellent. The lightweight carbon wheelset helps the Fatboy to feel much like any other cross-country hardtail.

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HED's lightweight carbon hoops are key to the Fatboy Expert Carbon's performance 


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The Fatboy Expert Carbon is race-ready out of the box

The Fatboy’s ride is more stable and a bit less spirited than bikes such as Trek’s agile Farley 9.8. If you’re interested in endurance racing the Fatboy is more forgiving when you’re fatigued, although it does require more input, and thus more energy, to coax though tight turns.

I specifically mention the Farley 9.8 because these two bikes come with comparable build kits and weight nearly the same, however the Farley costs significantly less than the Fatboy, making the latter a tougher sell.

Also consider:

Trek Farley 9.8

When going fast on relatively smooth fat-bike terrain is your focus, the Farley delivers with carbon everything and a smart design to make a silly light and surprisingly fast fat bike. Read our full Trek Farley 9.8 review.

Borealis Crestone

A gorgeous carbon frame and front suspension create a sleek companion for go-anywhere, do-anything jaunts on snowy trails and adventures. Read our full Borealis Crestone review.

Josh Patterson

Tech Editor, US
Josh has been riding and racing mountain bikes since 1998. Being stubborn, endurance racing was a natural fit. Josh bankrolled his two-wheeled addiction by wrenching at various bike shops across the US for 10 years and even tried his hand at frame building. These days Josh spends most of his time riding the trails around his home in Fort Collins, Colorado.
  • Age: 35
  • Height: 170cm / 5'7"
  • Weight: 68kg / 150lb
  • Waist: 72cm / 30in
  • Chest: 91cm / 36in
  • Discipline: Mountain, cyclocross, road
  • Preferred Terrain: Anywhere with rock- and root-infested technical singletrack. He also enjoys unnecessarily long gravel races.
  • Current Bikes: Trek Remedy 29 9.9, Yeti ASRc, Specialized CruX, Spot singlespeed, Trek District 9
  • Dream Bike: Evil The Following, a custom Moots 27.5+ for bikepacking adventures
  • Beer of Choice: PBR
  • Location: Fort Collins, CO, USA

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