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.
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.
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.
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