Specialized Fuse Pro 6Fattie

It was so odd to actually find green grass this time of the year in So Cal, due to some crazy rainstorms that moved through the area.

This is going to be a long term testing period, so we will do the Full Monty and break this review process out a bit.  I think this new tire size deserves a bit of careful scrutiny, don’t you?  So here are my initial impressions.


Now, remember we got this LG sized Specialized Fuse Pro 6Fattie Out Of the Box here.  Originally I was concerned because the XL I was expecting to arrive turned out to be a size Large, and looking at the geometry specs on the bikes, you can see that the XL has a HUUUUge top tube length paired with a quite short stem. But that fretting was for naught, for at 6’2″ and with long arms and only a 34″ inseam, the LG is a quite good fit for me for the type of bike it is.

After a preliminary fork set-up and such what, I set out with 15psi F/R in the tires and a smile on my face, pedaling off to the trail head.  Immediately I was taken by how surprisingly quick it feels when you go to accelerate.  It spins up pretty nicely on pavement and I already was thinking that riding this for a good ways on tarmac would not be a terrible burden, unlike my time on a Fat Bike. On the way to the dirt, there is a section of sand that washes into the nearby park from a drainage ditch.  It gets deep enough to where no ‘normal’ MTB, 29er, etc, can ride though it.  You will grind to a stop.  The Specialized Fuse Pro 6Fattie with those 3.0 Ground Controls just cruised though with only a bit of a wiggle off my intended line.  Cool!  I can tell that it is NOT quite a Fat Bike in this sense, and deeper sand would stop it eventually, but it is way more capable in this regard than a normal 29er.

Backcountry singletrack, So Cal style.

Backcountry singletrack, So Cal style.

On the way to the singletracks, the open gravel road once again showed that the 27+ tires feel anything but slow and kludgy.  I don’t think it has quite the rolling juggernaught feel of the 29+ Stache 9 we reviewed, but it floats over the loose gravel and sandy sections like they were not there.  Getting out of the saddle, I clicked down a gear or two on the SRAM 1×11 and took a quick right onto a singletrack.  Riding uphill against a gentle grade, the trail winds and snakes it’s way along, offering a surface that is akin to hardened concrete that was walked on before it set up.  Bumps combine with the slight grade to suck away momentum and if the bike is going to feel a bit plodding due to heavy wheels or what have you, I notice it here.

The Specialized Fuse Pro 6Fattie is anything but plodding and the big tires were doing something to lessen the bumpy trail.  Quick right-left turns and accelerations were easy to manage.  This is fun.  You can jive with the bike easily enough. Traction, as you can imagine, is pretty impressive, and cornering with those wide tires on our sun ravaged soil is almost casual.  Steering is not slow, exactly, but let’s say ‘damped’.  Inputs into the bar take a bit more ‘more’ to get the bike to respond and when it is there, on the line you chose, it tends to stay there without being ‘pinged’ away.  ‘Calm’ is the word as well, but not to the point of being boring or turning into a wrestling match.

Some other things I have noticed so far.

The Good:

  • Specialized Fuse Pro 6Fattie

    Although hardly death defying, rocky, rutted chutes like this are no match for a 3.0 tire at 15psi.

    It feels pretty ‘normal’.  And I say that, not just in comparison to a Fat Bike, but also compared to a typical 29er.  With an overall tire diameter (un-sagged) of 28.5″ or so, it does not have that huge wheel feel that the 29+ did for me.

  • It is very agile too.  That somewhat smaller yet still pretty big tire diameter lets you move the bike around and get a bit ‘aggro’ if you will.  Playful, is the word, as overused as that is. Although I am not a trail Ninja, I like to move the bike around and jazz dance a bit.
  • The tire and wheel combo is about a 1/4 pound heavier than the combo of a Roval Fatty alu wheel/180mm rotor/2.3 Ground Control (and allowing for sealant weight), so that is not bad at all.  I am always caught by surprise at how well it responds when you rise up to sprint a section of trail.  It’s pretty quick for a fatty-ish thing.
  • The handling feels very dialed. From slow speed trails in rock gardens all the way to 25mph rutted doubletracks filled with small rocks, I have yet to be surprised by a poor performance, although I did get some front end wander when climbing tight, slow singletrack.  Manageable though.
  • The Specialized Command Post (dropper post) now allows for more than two positions of ‘down’, so that is nice.  So far it has been excellent.
  • 1x on this bike really seems appropriate for general trail riding and kicking around, despite the inherent limitations of a single chainring.
  • Traction is pretty darn high, so cornering takes on new attitudes.
  • Line choice opens up to where you can almost ignore smaller ruts, loose rocks, and generally rubbly stuff as the Specialized Fuse Pro 6Fattie does not really care.  That is very cool.
  • I get very little self steer with it, especially if I stay around 15psi.
  • Stable.  Stable.  Stable.
  • Very comfy in and out of the saddle, impact wise.  Pretty cushy.  Baby head rocks just disappear under the tires like they were never there.

The Not So Good:

  • Plus bikes can get away with very little tread on the tires, at least for the most part, as the big footprint and low pressures put a ton of rubber in contact with the ground.  But the Ground Controls are not quite up for gnarlier trails on hard surfaces. The most annoying trait is a tendency for the rear tire to slide down into a parallel rut, typically when climbing, and stop your upward progress.  I don’t know if it is the tread pattern/sidewall knobs or the relatively narrow rim (as compared to other rim options in the + bike world) allowing the tire to flex around a bit rather than ‘bite’, but I did not notice this on the Stache 29+.  Annoying.  I have a Purgatory tire in the + size that I will toss on there, but I likely will run it front only, putting up with the somewhat loosey-goosey rear tire to keep things rolling faster.
  • There is a bit of moon bounce going on that seems like it will just be part of the deal with + bikes, at least at this point in tire development.  I also don’t think the Reba fork is quite tuned for the tire, but I do need to continue to tweak it a bit.  The PSI rating on the fork leg chart seem awfully high to me and there are times I can feel the front tire bounce right off the ground and move off my line a little bit.  It seems like less compression damping and more rebound might be the ticket to keep the fat tire managed.  These things are still being worked out as we go along.  The moon bounce was worse with 13psi in the tires (as you might expect) so even though 15psi was bit more than I really needed to run, it was a good compromise for all around happiness.  The back end can get a bit bouncy at speed on rougher trails.  It’s a hardtail.
  • It is not quite the rolling momentum wonder machine that the 29+ is, so if you ride where it is chock full of abrupt transitions, ledges, drops, etc, then 29+ still has the edge.
  • It’s not full suspension and you will still be reminded that you are on a hardtail, albeit a forgiving one.
  • 1X is nice and all, but a 30Tx42T combo may not be low enough for all day exploration rides on long, steep trails.


Specialized Fuse Pro 6FattieSo what is the deal…is this a real ‘thing’ or just a pretender?

Oh it’s the real deal IMO, But it is not for all people and for all places, but then what is?  For instance, the worse the soil conditions are, the better it gets, and I do not mean mud, although with the right tire, I bet that would be true as well, but as the surface degrades into rubbly, sandy, chunky crap then the Specialized Fuse Pro 6Fattie really shines.  If you are mostly on harder surfaces and fast, twisty, and buff trails, then the + tires are not doing as much for you.  However, if the cost of having them is low enough, then why not have them?

It is sooooo much fun to ride in the trail conditions I have now, post-So Cal summer.  The way it deals with roached trails; floating along while still allowing for a playful vibe. It lets you still ‘feel’ the trail and toss the bike around if you like.  It climbs well enough to where I would not hesitate to take it on epic rides unless they were just all day fireroad climbing stuff.  It descends well enough to give the guys on FS bikes grief if you have the skills, and the worse the soil conditions are, the better it likes it.

It is, actually, the most fun I have had on a mountain bike in a long time.  It also is likely to make the hardtail, much like 29ers did, even more relevant than ever, as the increased traction, forgiving ride, and stability go a long ways toward making it a viable ‘one bike only’ solution.

And it is just beginning.  I already have a bikepacking trip or two planned on it.  Plus bikes make crazy good adventure bikes, and the Specialized Fuse Pro 6Fattie should be fine for that type of trip.  I am thinking I need to get back to the WRIAD ride on it.  Kokopelli trail, perhaps?  Stagecoach 400?  Why not?  The Specialized Fuse Pro 6Fattie would be up to it, although my legs may not be.

Although I did get out on my FS 29er, just to do a quick comparo, the Specialized Fuse Pro 6Fattie is all I have been taking off of the garage hook for all my MTB rides of late and I do not see anything on the horizon that is likely to change that anytime soon. It will be interesting to see how this plays out on FS bikes.  I know I have seen some longer travel versions of 27+ but I do not think that will be the best app for this tire size.  There is just too much undamped-ness and tire squirm going on there, at least with the tires we are seeing now.  Will sidewalls be different as things get tweaked?  Maybe so.  Would a 27.5×26 tire be the hot ticket for a longer travel FS bike?  But keep in mind that as the tires get smaller, they lose diameter and footprint, so we are working backwards from what makes + bikes so unique.

How about an Epic or the new Camber with + tires? I would not expect an Epic+, but a Camber 6Fattie? I would bet on it.  Or maybe something like a Salsa Spearfish+?  Scott bikes did not (yet, anyway) show a Spark 27+ but they should.  I think 80mm-90mm rear and 100mm-120mm front on a bike like this would be fabulous (ala the Rocky Mountain Sherpa, which needs a bit of tweaking perhaps to be spot on).


Specialized Fuse Pro 6Fattie

JeffJ’s Stache and the Specialized Fuse Pro 6Fattie;  head to head, nose to nose.

Last night I was out for a typical after work cruise with JeffJ on the local stuff.  Trails we know well.  He was on his Stache 9 29+ (he liked it so much that he bought it and is replacing his Stache 8 with it) and I was on the Specialized Fuse Pro 6Fattie.  We were both remarking that going back to ‘normal’ sized tires at this point, at least for the kind of riding we were doing, would be hard to swallow.  JeffJ feels like this is the same type of paradigm shift he felt when he went from 26″ to 29″ wheels.

Interesting times, indeed, and this is just getting started.  For now, I am finding more things I like than things I do not like, both about the Specialized Fuse Pro 6Fattie specifically and for Plus as a genre.

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Note: Specialized provided this review bike at no charge to Twenty Nine Inches for test and review. We are not being paid, nor bribed for these reviews and we will strive to give our honest thoughts and opinions throughout.