Specialized Stumpjumper FSR Comp Carbon 6Fattie review

Plus-tired trail-taming bulldozer of a bike

Our rating 
4.0 out of 5 star rating 4.0
GBP £3,500.00 RRP | AUD $5,999.00 | USD $4,500.00

Our review

An insanely fun bike which, despite some flaws, is far more capable than you might give it credit for. Let the good times roll
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While the paint job is more muted than its 650b cousin, the 6Fattie Stumpjumper is a head-turner in its own right. The big tires are immediately noticeable, yet don’t look ridiculous – make no mistake, this isn’t a fat bike.


While the rubber is big and bulky, the carbon mainframe complements it with smooth lines and an impeccable finish.

Spec substitutions

Costing the same as the 650b Stumpy we rode alongside it in the Alps during testing, the 6Fattie gains a carbon frame to keep its weight in check at 14.02kg. With more money spent here, it’s no surprise to see lower-grade bits hanging off the frame.

Related: Specialized Stumpjumper FSR Elite 650b review

Shimano Deore brakes and a SRAM GX groupset perform virtually as well as their pricier counterparts, but the Performance-level 34 fork and Float shock from Fox lack the subtle control levels of the Pike and factory shock on the 650b. While the Roval rims are shared, the 6Fattie also has slightly cheaper, but Boost-width, Specialized hubs.

Wide tires, narrow rim:

Wide tires, narrow rim

Specialized’s carbon Stumpys now have the SWAT down tube storage port – under the bottle cage is a door in the tube, allowing you to stash items such as tubes, tools and, if you’re Spesh rider Mitch Ropelato at least, hot dogs. Some see it as a gimmick, but for lovers of pack-less riding, it’s a nice feature.

Rough-terrain gobbler

The 6Fattie’s carbon front end is shared with the 29er Stumpy, coming in a touch shorter than the 650b version, with a reach figure of 431mm (L). Despite this, the 6Fattie actually felt a better shape than the 650b version.

This is thanks to the BB drop – the distance below a line between the wheel axles that the BB sits. The 650b has an 18mm drop, whereas the 6Fattie sits 33mm below the axles, leaving you feeling like you’re sat much more ‘in’ the bike, rather than over it, making it confident when leaned over into a corner. At the back, the 148 Boost alloy rear end is a touch longer at 437mm, giving a little extra high-speed stability with the subsequent longer wheelbase.

The 6fattie stumpy’s head angle isn’t particularly slack, but the wide rubber helps it hold lines excellently at speed:

The 6Fattie Stumpy’s head angle isn’t particularly slack, but the wide rubber helps it hold lines at speed

The big story, though, is the chunky 6Fattie Purgatory and Ground Control tires. At three inches wide they offer far more volume than regular tires, and also stand taller over the rim, giving an outside wheel diameter similar to that of a 29er. The result is a bike that gobbles up rough terrain and spits it out the back far more proficiently than you might imagine, holding momentum, but still managing to maintain plenty of agility.

The tires are mounted on 29mm internal width rims – of all the plus bikes we’ve ridden, these are the narrowest-mating we’ve experienced. While we worried about excessive tire roll, the Control casing did a reasonable job, although in big compressions, or where we needed to load the front wheel to hop the rear round a switchback, there was a definite element of roll. On most trails though, our testers rarely noticed any issues.

A bike that rips on most trails

The large volume and low pressures (around 14psi) means the tires conform well to rough surfaces, giving a lot of grip – something that’s especially noticeable on technical climbs. Where grip wasn’t as we expected was on mud: the lack of a particularly aggressive tread meant the tires didn’t dig in as well as we’d have liked.

On heavily front wheel loaded, slow speed technical sections, the large air volume also gives a sense of disconnect between the tire and bike, while hitting roots at speed can result in a slightly pingier rebound than we’re used to – something which we found ourselves adjusting to.

The 6fattie is a point-and-shoot ripper on most trails you put in front of it:

The 6Fattie is a point-and-shoot ripper on most trails you put in front of it

On the majority of trails though, the 6Fattie rips. It’s definitely a point-and-shoot bike, rather than threading like a needle through techier sections, but the big wheels bound over terrain like a collie dog on speed. You’ve just got to let the brakes off, hold on and scrub your speed at the end of the section.

The masses of grip up front means braking points can be later, while the shoulder tread of the Purgatory tire and the low BB means it’ll hang on in fast corners, allowing you to carry heaps of speed. The 67-degree head angle might not be slack, but the big tires mean it holds a line with absolute steadfastness.


While there’s definitely a lag between putting a sprint effort in and the bike accelerating up a hill, if you’re happy to sit and spin the 28t chainring, the 6Fattie doesn’t feel too bad on longer smooth climbs either. The tires are heavier, but the low tread rolls nicely on tarmac.

Also consider:

Rocky Mountain Sherpa

Built for bikepacking deep in the backcountry, the carbon framed Sherpa was one of the first full-suspension plus-size bikes. See our full Rocky Mountain Sherpa review.

Scott Genius LT 710 Plus

Want an agile, enduro-ready beast that makes the most out of the big rubber/long travel equation? See our full Scott Genius LT 710 Plus review.

Product Specifications


Name Stumpjumper FSR Comp Carbon 6Fattie
Brand Specialized

Seatpost Command Post IRcc
Headset Type Hella Flush
Frame Material FACT 9m carbon, Trail 6Fattie Geometry
Front Hub Specialized, Hi Lo disc, sealed cartridge bearings, 15x110mm thru-axle, 24h
Front Tyre Specialized 6Fattie Purgatory Control, 60TPI, 2Bliss Ready, folding bead, 650bx3.0"
Grips/Tape Specialized Sip Grip, light lock-on, half-waffle
Handlebar Specialized, butted 6000 alloy, 10mm rise, 750mm
Head Angle 67
Pedals Nylon, CEN std., w/ toe clips
Cranks Custom SRAM GX-1000, carbon, PF30 spindle, 28T, direct mount
Rear Derailleur SRAM GX X Horizon, 11-speed, alloy cage
Rear Hub Specialized, Hi Lo disc, 4x sealed cartridge bearings, 12x148mm thru-axle, 28h
Rear Shock FOX FLOAT Performance DPS, AUTOSAG
Rear Tyre Specialized 6Fattie Ground Control, 60TPI, 2Bliss Ready, folding bead, 650bx3.0"
Rims Roval Traverse 650b, alloy, disc, 29mm wide, 24/28h
Saddle Body Geometry Henge Comp, hollow Cr-Mo rails, 143mm
Fork FOX 34 Plus Performance
Chain KMC X11L, 11-speed, w/ reusable MissingLink
Shifters SRAM GX, 11-speed, trigger
Chainstays (in) 17.2
Stem Specialized XC, 3D forged alloy
Trail 9.65
Weight (kg) 14.02
Brake Levers Shimano Deore BL-M615, I-spec compatible
Spoke Type DT Swiss Industry, stainless
Bottom Bracket Height (in) 13.03
Seat Tube (in) 18.43
Cassette SRAM XG-1150, 11-speed, 10-42t
Standover Height (in) 30.31
Top Tube (in) 24.25
Wheelbase (in) 46.42
Frame size tested L
Available Sizes S M L XL
Bottom Bracket SRAM, PF30, OS press-in bearings, sealed cartridge
Brakes Shimano Deore, hydraulic disc, Ice-Tech resin pads w/ fins
Seat Angle 74