Specialized Stumpjumper Comp Alloy 6Fattie first ride review$2,800.00

Rides like a Specialized and that's a good thing

When you think of a Specialized mountain bike, chances are the Stumpjumper comes to mind. Back in 1981 the original Stumpjumper was the first ever mass production mountain bike. Since then, Specialized has offered countless variations, and for 2018 the Stumpjumper Comp Alloy is offered with 29-inch or 27.5+ wheels and tires.

Specialized Stumpjumper Comp Alloy 6Fattie features

  • Frame: M5 aluminum, 135mm travel
  • Fork: RockShox Reba RL, 150mm travel
  • Drivetrain: SRAM GX 11-speed w/Race Face Aeffect cranks
  • Wheels/tires: Roval Traverse 27.5, Specialized Purgatory 3.0in (front), Slaughter 2.8in (rear)
  • Brakes: SRAM Guide R

The aluminum frame features smooth welds, plus super svelte internal routing holes
The aluminum frame features smooth welds, plus super svelte internal routing holes

Tire traction and weight

There's no shortage of Stumpy options, Specialized lists 18 different bikes and frames for 2018. One of the big selling points, or possibly just a point of difference, of 27.5 plus tires (Specialized calls them '6Fattie' for some weird reason) over 29er or 27.5in tires is the increased traction from the big, wide tires. 

Up front, the 3.0in Purgatory tire rolls with the big S's Gription compound and Grid puncture protection
Up front, the 3.0in Purgatory tire rolls with the big S's Gription compound and Grid puncture protection

But that traction comes with rolling weight. The Stumpjumper Comp Alloy 6Fattie rolls on a 3.0in Purgatory front tire and a 2.8in Slaughter semi-slick rear tire. According to Specialized, the Purgatory weighs 1,100g, while the Slaughter tips in at 1,040g.

First ride impressions: cushy and capable

One thing that Specialized has nailed is how its bikes ride. The California company has loved the short back-end, low bottom bracket style of mountain bikes and honed its fleet to feel a certain way. 

RockShox's Monarch RT controls 135mm of rear end travel
RockShox's Monarch RT controls 135mm of rear end travel

That's a good thing. The big S's ride feel is fun and playful, sometimes at the cost of efficiency. This alloy version certainly is that. 

The big tires rolled well. They're far from fast, but quicker than my eyes lead me to believe. I had the rear at 19psi and the front at 16psi. They did feel bouncy and a bit vague when leaned over.

When landing little jumps or weighting into a corner, I could feel the sidewalls squirm and fold, so some experimentation is needed. The air pressure gauge is going to see lots of use I reckon. 

A 150mm travel RockShox Reba RL 29er fork is fitted
A 150mm travel RockShox Reba RL 29er fork is fitted

On the front, the RockShox Reba RL fork seemed a little overwhelmed with the big 3.0 tire pushing it around. It's a 150mm travel 29er fork, so its length is a bit much for the 32mm stanchions to keep in line. 

Out back, the RockShox Monarch RT employs Specialized's Autosag, which on paper is supposed to dial in the correct rear shock air pressure. I set it up as instructed but like most shocks the average baseline for my weight is way too soft for my riding style. With too little pressure I found the bottom of the stroke numerous times. 

Pointed downhill, the Stumpjumper Comp felt both smooth and a bit vague. The big tires certainly smashed small trail imperfections, but also lacked the precision and predictability of a good, squared-off tire. Again, air pressures will need to be played with.  

Other than the wheels and tires, it was standard Specialized business; easy to steer from the bottom bracket and eager to boost and loft over anything in its path. 

Spin to win

With a 28t chainring, Specialized gives a nod to how this Stumpy should be pedaled. And that's spinning, not smashing. The huge amount of traction as well as the FSR rear end worked better with a consistent, smooth cadence. 

A steel 28t chainring is tied to a Race Face Aeffect crank
A steel 28t chainring is tied to a Race Face Aeffect crank

When pedaling like jackhammer, or in too big of a gear, the rear shock bobbed and the bike squatted a bit before squirting forward.

On the flip side, those tires and rear-end gave the Stumpjumper Comp goat-like climbing ability. Over loose, square rocks, the cushy tires found purchase and the FSR suspension tracked every bump. Keep the pedals moving and there seems little this bike couldn't ascend. 

Specialized Stumpjumper Comp Alloy 6Fattie pricing and availability

This amply named Stumpy retails at £2,500 / $2,800 / AU$TBD and can be found at local bike shops. 

Russell Eich

Tech Writer, US
Russell fell head over heels in love with bikes in the '90s, and has been involved in the bike industry ever since. Between wrenching in bike shops, guiding professionally, and writing about bikes, Russell has honed an appreciation for what works, gained knowledge of what doesn't, and can barely contain his enthusiasm for what comes next. His two-wheeled passion continues in the Rocky Mountains high above Boulder, Colorado.
  • Age: 39
  • Height: 6'3"/190cm
  • Weight: 175lb/79kg
  • Waist: 34in/86cm
  • Chest: 42in / 107cm
  • Discipline: Mountain, road, cyclocross
  • Preferred Terrain: High altitudes, forgotten singletracks, bike parks, roads without cars
  • Current Bikes: Custom Meriwether steel hardtail, Specialized S-Works Enduro 29, Kona Jake the Snake, Trek 69er, and a bunch more
  • Dream Bike: Yeti SB5c, Intense Tracer 275C, Black Cat custom road
  • Beer of Choice: Gin + Tonic
  • Location: Rollinsville, CO, USA

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