The plus-sized Specialized Stumpjumper FSR Expert 6fattie is ready to rumble

Big 3in tyres promise heaps of grip and lots of speed

It was just a few weeks ago that I was smitten by Specialized’s flagship S-Works Stumpjumper FSR 6fattie plus-sized trail bike – the copious grip, the cushy ride, the freakishly composed feel of those 3in-wide tyres… and a price tag well beyond reach of most riders.

The second-tier Stumpjumper FSR Expert 6fattie is still a lot of money but with so few performance compromises made in the process, it’s akin to hitting the trail packing only a teensy bit extra around the middle the day after Thanksgiving – while having a fair bit left over in your wallet.

The Stumpjumper FSR Expert 6fattie boasts the exact same carbon fibre front triangle, welded aluminium rear triangle, and 135mm/150mm front/rear suspension travel (albeit with a slightly downgraded Fox rear shock and fork) as its top-end sibling. Naturally, the build kit is also subtly toned down, most notably with the aluminium (instead of carbon) Roval Traverse wheelset, SRAM X1/XO1 transmission, and Shimano Deore XT disc brakes.

The rear end features 135mm of travel via specialized's long-running fsr four-bar layout: the rear end features 135mm of travel via specialized's long-running fsr four-bar layout
The rear end features 135mm of travel via specialized's long-running fsr four-bar layout: the rear end features 135mm of travel via specialized's long-running fsr four-bar layout

The Specialized Stumpjumper FSR Expert 6fattie continues on with the company's long-running four-bar suspension layout

As a result, you get essentially the same great handling, proven suspension design, and tyre traction features of the top model but with a bit of extra weight. Fully equipped with a bottle cage and Specialized’s neatly hidden SWAT chain tool and mini-tool, actual weight is just 12.92kg (28.48lb) – less than a pound heavier than the S-Works version and still remarkably light all things considered.

I’m just a few days into testing but so far, that initial revelatory experience is carrying over. Simply put, this thing is outrageously fun to ride. There’s incredible traction, it’s ridiculously comfortable, and most surprisingly, it’s proving to be silly fast with very noticeably reduced rolling resistance as compared with even top-end conventional trail wheels and tyres, particularly on bumpier and rockier trails.

Whereas many plus bikes come with low-profile tires to boost their rolling speed, specialized wants to maximize the traction of the stumpjumper fsr expert 6fattie with properly meaty treads: whereas many plus bikes come with low-profile tires to boost their rolling speed, specialized wants to maximize the traction of the stumpjumper fsr expert 6fattie with properly meaty treads
Whereas many plus bikes come with low-profile tires to boost their rolling speed, specialized wants to maximize the traction of the stumpjumper fsr expert 6fattie with properly meaty treads: whereas many plus bikes come with low-profile tires to boost their rolling speed, specialized wants to maximize the traction of the stumpjumper fsr expert 6fattie with properly meaty treads

While many plus bikes come with low-profile tread designs to help with rolling speed, Specialized thankfully specs meatier tyres for better grip

I have also noticed, however, that getting the tyre pressure right on this plus-sized beast is absolutely critical. Too little and you end up with heaps of casing roll and uncomfortably vague handling; too much and you miss out on the traction benefits of ‘plus’ but still have to carry the extra rotating weight. That window is exceptionally small, too – just 1-2psi, and it’s conditions-dependent.

Further complicating that game is Specialized’s decision to spec such comparatively narrow rims on the 6fattie. Whereas other plus-bike makers are going with rims with internal widths of around 45-50mm, these are a scant 29mm and offer minimal support to the balloon-like tyre casings.

One of the neatest features of the specialized stumpjumper fsr expert 6fattie is the so-called swat box, which basically lets you carry whatever you can stuff inside the down tube: one of the neatest features of the specialized stumpjumper fsr expert 6fattie is the so-called swat box, which basically lets you carry whatever you can stuff inside the down tube
One of the neatest features of the specialized stumpjumper fsr expert 6fattie is the so-called swat box, which basically lets you carry whatever you can stuff inside the down tube: one of the neatest features of the specialized stumpjumper fsr expert 6fattie is the so-called swat box, which basically lets you carry whatever you can stuff inside the down tube

So just how much stuff can you put in the SWAT box? 

Ultimately, it’s a bit of a paradox that ‘plus’ is pegged as the ultimate solution for newer riders but that setup is so tricky, at least in this case.

That all said, now that I’ve got the pressure pegged for my local conditions (15-16psi here on the Colorado Front Range), it’s all systems go. Check back soon for a full review but given that I’m not exactly eager to give it back, be warned that this one might take a little longer than usual.

For more information, visit www.specialized.com.

James Huang

Technical Editor, US
James started as a roadie in 1990 with his high school team but switched to dirt in 1994 and has enjoyed both ever since. Anything that comes through his hands is bound to be taken apart, and those hands still sometimes smell like fork oil even though he retired from shop life in 2007. He prefers manual over automatic, fizzy over still, and the right way over the easy way.
  • Discipline: Mountain, road, cyclocross
  • Preferred Terrain: Up in the Colorado high-country where the singletrack is still single, the dirt is still brown, and the aspens are in full bloom. Also, those perfect stretches of pavement where the road snakes across the mountainside like an artist's paintbrush.
  • Beer of Choice: Mexican Coke
  • Location: Boulder, Colorado, USA

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