First Look: Specialized Stumpjumper and Rhyme FSR 6Fattie

Stumpjumper and Rhyme FSR gain a version with 3.0 wide tires

27.5 All Mountain Trail Plus
Specialized FSR 6Fattie maximizes control.

Specialized FSR 6Fattie Rhyme maximizes control (click to enlarge).

What is it?

The FSR 6Fattie is a version of the Specialized Stumpjumper and Rhyme full suspension bikes that features 27.5+ tires sized at 3.0 inches. This gives the tires an outer diameter that is very close to the 29er at only a few millimeters smaller. To fit these in, the rear axle used is the Boost 148mm and the front is 110mm.

But why?

The customer will either exclaim ‘Hallelujah’ or ‘Why?’ The reason for all this commotion is traction, comfort and control. These attributes are critical to a mountain biker’s enjoyment of the sport. It’s safer too. And when all these elements conspire together, the rider usually has more fun.

Some riders caught a glimpse of these attributes with fat bikes. Riders were able to have fun and go on many mountain adventures in all sorts of terrain and weather conditions. But when the weather was not particularly harsh, 4.5 inch tires were sometimes overkill and carried the burden of slower speeds and less agility.

But 3.0 tires with wide rims seem to achieve a happy medium of flotation, traction and fun.

Specialized FSR 6Fattie  features no seatstay bridge to maximize tire clearance and minimize chainstay length

Specialized FSR 6Fattie features no seatstay bridge to maximize tire clearance and minimize chainstay length (click to enlarge).

Test ride

We got to ride some Stumpjumper 6Fattie prototypes and we even got to do back to back loops with a 29er spec’d with identical components.

The first impression is uphill speed is about the same. It’s really hardly noticeable as lab measurements at peak climbing power (250-300 watts) identify the power loss with the big tires to about 7 watts. Climbing very smooth terrain, the power loss might be more significant. But when climbing very rocky/rooty terrain, the 6Fattie will climb more efficiently since it will have more traction and bump absorbing characteristics.

Descending, there is more traction. Even with these puny knobbed Ground Control tires, traction was available in spades and it was hard to explore the limits and break the tires free. The dilemma here is it is more difficult to receive feedback from this tire with vibrations muted by low tire pressures. So the rider has to retrain and relearn a bit to actually find the limits of these 3.0 tires. But the upside seems much higher and better downhill speeds can be achieved by these setups.

Our other observation riding these bikes is there is much less vibration and chatter on the hands and arms. There is much less hand fatigue and arm pump. On longer descents like the Downieville Shuttle Run or the Top of The World Trail in Whistler, BC, this can be a distinct advantage.

Specialized FSR 6Fattie tire is 3.0 in size and is typically run at 14 psi.

Specialized FSR 6Fattie tire is 3.0 in size and is typically run at 14 psi (click to enlarge).

Price (Model – MSRP)

The FSR 6Fattie efforts are legitimate. Specialized is going ‘all in’ on this wheelsize and is coming in hot with two models and seven distinct specs.

SJ FSR SW 6Fattie – $8,600
SJ FSR Expert 6Fattie – $6,300
SJ FSR Comp Carbon 6Fattie – $4,300
SJ FSR Comp 6Fattie – $3,400

Rhyme Expert 6Fattie – $6,300
Rhyme Comp Carbon 6Fattie – $4,300
Rhyme Comp 6Fattie – $3,400

Continue to page 2 for more on the 6Fattie FSR and a full photo gallery »

About the author: Francis Cebedo

The founder of mtbr and roadbikereview, Francis Cebedo believes that every cyclist has a lot to teach and a lot to learn. "Our websites are communal hubs for sharing cycling experiences, trading adventure stories, and passing along product information and opinions." Francis' favorite bike is the last bike he rode, whether it's a dirt jumper, singlespeed, trail bike, lugged commuter or ultralight carbon road steed. Indeed, Francis loves cycling in all its forms and is happiest when infecting others with that same passion. Francis also believes that IPA will save America.


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  • Peper says:

    I’m another rider wondering why we aren’t seeing 2.6, 2.7 or 2.8 tires on regular rims in regular forks and drop outs.

  • Pete Schwind says:

    I ordered my Trek Stache 7 last week. And for a guy like me who buys a new bike every 8 years or so, I could care less that some are pissed about new standards like the hub sizing. Good job Specialized, I welcome evolution.

  • Gambit21 says:

    Brian Woodward
    “I’m sure they grip, but they won’t rail turns”

    Umm…incorrectamundo

    • Ian says:

      I can verify. I own a carbon Salsa Beargrease, and that thing handles loose turns better than any other bike I’ve owned.

  • Sun says:

    On the rocky slippery constantly shifting AM terrain that I ride on, I feel this 27+ size could be a real advantage and result in a faster more compliant ride.

    In the meantime I have a lot of money in my current bike and I’d like to see some 2.4-2.75 options to go on my current frame.

  • Izzy says:

    So, 29er sub-frame up front with a dedicated 27.5+ rear sub-frame?

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