Specialized Fatboy Comp Carbon review

One of the fastest fatties out there

Our rating 
4.0 out of 5 star rating 4.0
GBP £2,500.00 RRP | AUD $3,299.00 | USD $3,200.00

Our review

Despite a couple of component niggles, the Fatboy has huge potential to dominate any fat bike race
Buy if, You want a fast, capable and well-appointed fatty to race with
Pros: Light, speedy, well finished and perfect for mile-munching
Cons: You'll want to switch the stock tyres for snow, 203mm rotors are overkill, gearing is a little narrow
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The Comp Carbon Fatboy is Specialized’s second raciest fat bike offering, after its flagship S-Works version (in the UK at least – elsewhere the Expert Carbon strikes a midpoint between the two). The Comp Fatboy boasts the same lightweight FACT carbon frame as its pricier siblings.


It’s nicely finished with internally routed everything, even the front brake. In the name of weight reduction the Comp Carbon is only available with a matching carbon rigid fork, which weighs in at an impressive 637g of the overall 12.92kg. The tapered head tube and 150mm front hub spacing does mean this is RockShox Bluto suspension-compatible should you feel the need for it.

All cables, including the front brake, are internally routed:
Matt Orton / Immediate Media

All cables, including the front brake, are internally routed

The drivetrain is a mashup of parts with a 10-speed XO rear derailleur, wide range 11-40 Sunrace cassette, Race Face Turbine Cinch Cranks with 28t chainring and an X9 trigger. Rolling stock is Specialized’s own with 90mm Stout XC Rims laced to Stout XC Hubs and clad in 4in Ground Control tyres. The stopping duties are performed by Shimano Deore brakes leaving the remaining finishing kit to various Specialized XC alloy offerings.

Rigid for racing

Full fat and rigid is the best way to ride on snow. We found that suspension is unnecessary and not worth the additional weight penalty.

The 90mm wide Stout XC rims are wider than we’d want for regular trail riding, but help spread the tyre for maximum traction on the white stuff. That said the stock 4in Ground Control tyres are pushed to their limit and their profile becomes squarer and cornering suffers as the shoulder tread is pushed inwards. So we swapped out the tyres for the 5in versions, which we found to be a huge improvement both on and off the snow.

We swapped out the stock 4in Ground Control rubber so as to get a more rounded profile:
Matt Orton / Immediate Media

We swapped out the stock 4in Ground Control rubber so as to get a more rounded profile

The conservative angles of the Fatboy put it firmly in the ‘long day in the saddle’ XC bracket. The steep 70.5 degree head angle puts you in a good position for attacking twisty climbs and cranking through the flat sections. The rigid fork kept the head angle from steepening any further when descending, though, which meant it didn’t feel too steep when tackling sweeping trails and fast switchbacks.

With that 11-40t range, the drivetrain was enough for most climbs, save the second day’s brutal climb to Egli Station, when a lower gear would have come in handy. Similarly, the 28t chainring didn’t provide a high enough gear for flat-out racing at the other end of the cassette.

Views like this are worth a little effort:

Views like this are worth a little effort

Despite the lack of range, shifting was clean and precise, and not having to shift between front chainrings kept the momentum up when racing, as well saving a load of weight.

Too much braking

Shimano’s Deore brakes performed consistently well in the cold. With temperatures dropping below -10ºC, the hydraulics weren’t affected noticeably. Specialized’s choice of 203mm rotor at the front feels odd, though. The large rotor seems hugely overpowered for a fat bike, especially one that’s likely to see action in the snow.

Braking in snow is a fine art where anything more than feathering the front brake could easily wash out your front end, and the larger rotor needs additional calliper mounting brackets and bolts, which adds weight unnecessarily. The Deore brakes are powerful enough with 160mm rotors, and we’d sooner see a pair of those on the Spesh.

The lightweight FACT carbon frame is nicely finished – or was until one of our testers slapped a ‘Matt the Beard’ sticker on there:
Matt Orton / Immediate Media

The lightweight FACT carbon frame is nicely finished


The finishing kit is functional and comfortable, with the choice of Specialized’s Body Geometry Henge Comp saddle being particularly welcome. Although a wide carbon bar and a carbon seatpost would complement the frame and fork for the ultimate race-ready package, a dropper post would’ve been the most useful upgrade for this event. Overall, on snow the Specialized felt fast and comfortable too.

Product Specifications


Name Fatboy Comp Carbon
Brand Specialized

Description Geometry based on size 'Large'
Rear Tyre Specialized Ground Control, 120TPI, 2Bliss Ready, folding bead, 26x4.0"
Top Tube (in) 24.65
Standover Height (in) 30.64
Seat Tube (in) 18.5
Chainstays (in) 17.91
Bottom Bracket Height (in) 12.09
Spoke Type Stainless, butted, 2.0/1.8/2.0mm, black
Brake Levers Shimano Deore BR-615, hydraulic, reach adjust
Trail 8
Stem Specialized XC, 3D forged alloy, 4-bolt, 6-degree rise
Shifters SRAM X9, 10-speed, trigger
Seatpost Alloy, 2-bolt, 12.5mm offset, 30.9mm, anti-corrosion hardware
Seat Angle 73
Saddle Body Geometry Henge Comp, hollow Cr-Mo rails, 143mm
Rims Specialized Stout XC 90, disc, alloy, single wall, 90mm wide, sleeve joint, hookless design
Rear Hub Specialized Stout XC 197, Hi Lo disc, alloy, sealed cartridge bearings
Available Sizes S M L XL
Rear Derailleur SRAM X0 Type 2.1, 10-speed, long cage
Pedals Alloy, 1 pc. body, 9/16", w/ reflectors
Head Angle 70.5
Handlebar Specialized XC, butted 6061 alloy
Grips/Tape Specialized Sip Grip, light lock-on, half-waffle
Front Tyre Specialized Ground Control, 120TPI, 2Bliss Ready, folding bead, 26x4.0"
Front Hub Specialized Stout XC 150, Hi Lo disc, double-sealed cartridge bearings
Frame Material Specialized FACT 10m carbon, tapered head tube
Fork FACT carbon, tapered steerer, 150mm dropouts, internal brake cable routing
Cranks Race Face Turbine Cinch, PF30 BB, 100mm spindle, 28T direct mount ring
Chain KMC X10L, 10-speed, w/ reusable MissingLink
Cassette Custom Sunrace, wide range, 10-speed, 11-40t
Brakes Shimano Deore, hydraulic disc, resin pads, Ice-Tech rotor
Bottom Bracket Carbon PF30
Wheelbase (in) 44.69