Short by modern standards but upsizing is easy.
The Specialized Stumpjumer has been the trail bike of choice for the last 10 years. And like any great prize fighter, it’s held titles in multiple classes; transitioning easily from 26in to 29in, then slimming back down for a less-than-successful debut in 27.5in.
The latest version is the Stumpy 6Fattie. At 31.3lb with a carbon front end, the 135mm travel 6Fattie is the heaviest Stumpy to date. But will it still prove fast enough to out manoeuvre the competition?
At the weigh-in, the 6Fattie was smidge heavier than expected, but the difference was mostly in the tyres — the 3.0in Purgatory and Ground Control having much more rubber on the sidewalls. Not only does this reduce the risk of puncturing, it also gives the tyres more damping, resulting in a less bouncy ride.
It’s in the reach measurement, however, where Specialized really loses ground. At 431mm for a size L, the 6Fattie is short by modern standards. Fortunately, standover clearance on the 6Fattie is excellent, so upsizing is easy. Our sizing recommendation is to put an upper limit on the Large 6Fattie at 5ft 9in.
Specialized Stumpjumper FSR Comp Carbon 6Fattie is probably the longest model name of any mountain bike, but as Plus bikes go it’s got relatively short chainstays. Specialized achieved this by eliminating the seatstay bridge for extra clearance at full travel. To offset any loss in stiffness, the stays and upper suspension link have been beefed up substantially.
Was it worth the trouble? Well, the shorter stays definitely make it easier to loft the front end, with the flipside being that it compounds the sizing issue, by making the bike feel even shorter than it is.
Anything that simplifies getting a ballpark suspension set-up is a bonus, so we’re big fans of Specialized’s Autosag feature. On the 6Fattie however, there’s simply not enough progression in the Fox Float shock to run the correct amount of sag. If you do, the bike rips through its 135mm travel in the blink of an eye, bottoming too easily and too often. Also, you’ll be forever grounding out pedals with the ultra-low 326mm BB.
It’s a similar story with the 150mm travel Fox 34 Float fork. Sure, it’s sensitive and plush off the top, but it dives too readily under braking, something that’s compounded by the extra traction afforded by the beefy 3.0in tyres.
There are no fancy parts adorning the 6Fattie, but everything is functional and perfectly placed. The 750mm bar has a nice profile, and the 60mm stem is short enough.
With its new micro-adjust feature, the action of the 125mm Command Post IRcc now rivals the RockShox Reverb, and we even prefer Specialized’s under bar remote. Reliability is still an issue though; the wiper seal popped out after just three rides.
We couldn’t have been happier with the performance of the 6Fattie on flat, flowing singletrack or constant gradient descents. It felt playful and lively — the Plus size tyres giving some extra pop to the ride while devouring everything in their path.
Take the 6Fattie into more challenging terrain, however, and it wasn’t long before the shock pump was out and we were tweaking pressures. With the Plus tyres and super supple suspension, it certainly wasn’t increased grip or comfort we sought. What we craved was more chassis stability, and a set-up that was less easy to unsettle.
We tried running the rear shock and fork in the mid-compression settings, and while this worked well for the rear suspension — giving the bike a tighter more reactive ride — it just made the fork feel more unpredictable under braking or when bump forces got high enough to overcome the damping threshold.
Once we fitted volume spacers to the shock and fork, balance was restored, and the focus shifted back to the sizing, or rather the lack of it. The size Large being more akin to a size Medium.
With its slack head angle, lower bottom bracket and more active suspension, the Specialized 6Fattie has the edge on most Plus sus bikes, just. It’s been sold short however, as it would be even better if the front end was 20mm longer. Yes, the suspension needs tightening up with the addition of volume reducers, and it’s fair to say, when you’re dropping £3.5k on a bike, someone at Specialized really should have taken the time to ensure that the suspension is totally dialled straight out of the box. Luckily, it’s a super-easy and inexpensive fix that takes the 6Fattie to the next level.