2015 Specialized Stumpjumper FSR Comp Carbon 6Fattie

Tire Pressure

Tire pressure always matters, but on bigger tires, small changes are critical and really affect the overall ride quality of the bike.

I found more than 17 psi to be very firm. 13-15 psi was my sweet spot. If I wanted to be safe from flats, I’d run 15-17 psi in the rear. I’d run 13-15 psi in the front all the time. The only exception to this was if I wanted to ride a jump trail. On a jump trail, the tires could get really squirmy, so I’d pump them both up to 17+ psi.


I was a bit surprised by how many issues I had with this bike.

From day two, the headset creaked and made terrible noises. After tightening, then greasing the interfacing surfaces, I finally tracked down the issue to two problems. First, the aluminum star fangle (most are steel), and the aluminum top cap bolt are weaksauce. The fangle slipped under the lightest pressure, and I couldn’t keep the headset tight. Additionally, and possibly caused by the first issue, the seal on the bottom bearing became deformed and slipped out of place. Popping it back into place and swapping the aluminum headset tension assembly for a standard steel bolt and fangle combo resolved both issues, and it has been trouble free since then.

What was Specialized thinking by spec’ing this combo?! It can only save a few grams, and it is non-functional. It is pretty easy to replace, but you shouldn’t have to. Every other bike I’ve ridden has had an adequate star fangle and bolt.

The rear tire started leaking sealant very early on. The sidewall is very thin to keep the weight reasonable. After 15 days of riding or so, it started losing sealant through the sidewall pretty quickly. I swapped from the Specialized sealant to Stan’s, and found that both moved through the sidewall at the same rate. The tire was okay for flat resistance, but too thin for wear. I got one flat on a rock when the pressure had dropped a bit low

Tom Collier reviews the Specialized Stumpjumper FSR Comp Carbon 6Fattie for Blister Gear Review.
Specialized 6Fattie sealant leak

The seal on the dropper post popped out of place. I was able to replace it by pushing on it with a tire lever. The post never stopped working, but it is slightly noisier now.

The rear shock worked okay, but the lockout lever kept switching to the middle setting by accident, and I caught my shorts on the pressure release valve with some frequency.

Notably, I’ve not had any creaking out of the pressfit bottom bracket. That said, it hasn’t seen much wet weather, and it isn’t all that old. So we’ll see.


Vs. Scott Genius Plus

The Scott Genius Plus is very similar in travel and geometry to the Specialized Stumpjumper. So I imagine many potential plus-bike-purchasers will find themselves with both bikes on their short list. The suspension on the Specialized is a bit more active during braking and in the rough due to the horst link design. However, I did find the Scott to have better bottom-out control, permitting more aggressive riding in challenging terrain. The Specialized was a bit more playful and had a bit more pop. If you do want to rail turns, you should either buy the Scott, or upgrade to wider rims on the Stumpjumper.

Vs. Scott Genius LT Plus

The Specialized Stumpjumper 6Fattie is a much more nimble bike than the Genius LT Plus. In large part, this is because the wheelbase is much shorter and the headangle much steeper. Conversely, the Scott has much better control on rough terrain because of those same attributes. With 160 mm travel and big tires, the Genius LT is even a bit closer to a downhill bike than other long-travel trail bikes. But it is not the most fun bike on flatter and / or smoother trails.

As with the Genius Plus, I appreciated the wider rims and slightly smaller tires vs. the Stumpjumper.

Vs. Santa Cruz Nomad 

The Stumpjumper is more playful than the Nomad, and surprisingly capable despite having less travel. The big tires smooth out the ride impressively well through small chunder, but the bike is much more limited in its ability to handle large hits.

When riding a challenging trail on the bleeding edge of control, I’d rather be on the Nomad. The suspension handles big hits better, the geometry is more stable, and normal tires mean that I can cut harder and change direction better in tough situations.

However, especially for beginner or intermediate riders, the Nomad can be a bit hard to handle, while the Stumpjumper inspires confidence.

Vs. Santa Cruz 5010

The Stumpjumper can’t hang with a Nomad or similar bikes in nasty terrain, but neither can the Santa Cruz 5010. The 5010, however, pedals better and is more playful on mild terrain. In many ways, the Stumpjumper is a similar bike. It is more fun on milder terrain than the Nomad, but unlike the 5010, the Stumpjumper doesn’t offer much more efficiency than the Nomad.

The Stumpjumper is more capable on rough terrain than a 5010 both because it has more travel in front (150 mm vs 130 mm), and because it has bigger tires that add traction and cushion. Given the option to ride either one on any given day, I’d choose the 5010 for fast and / or long rides, and the Stumpjumper for shorter, more technical rides.

NEXT: Wheel Size Experiments, Which Model, Etc.

5 comments on “2015 Specialized Stumpjumper FSR Comp Carbon 6Fattie”

  1. Sort of minor question…. the Specialized dropper lever is not compatible with a thomson? I’ve used one with mine for a year. Definitely a bit of a pull but works fine.

    • I know Thomson changed their setup at some point last year and flipped around how the cable is oriented. The post I have requires the swaged cable end to attach at the bottom of the post. The Specialized lever requires that the swaged end terminates at the lever. If you are determined, you could swage a second end onto the cable and make it work, but short of that it isn’t easily compatible.

  2. Great review. Love the depth. Every Specialized I’ve owned has been expensive — from pedal replacement costs due to their ridiculously low bottom brackets. No easy fix for taller guys, either.

    OTOH, it’s much easier to add a volume reducer to a Fox shock to reduce bottoming than it is to remove a non-existent one due to excessive ramp up. I like S’s approach in this regard.

    • Thanks Tom. I agree that it is easier to add a reducer than remove a non-existent one. I hope to add one to this bike to try it out. I’m not sure whether or not I’ll be able to get enough ramp though. It is very deficient and the shock already has a stroke reducer in it so I’m not sure how much I’ll be able to fit in there in terms of spacers.

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