First Look: WTB and Rocky Mountain Team Up For 27.5″ + Adventure Bike Prototype

Rocky Mountain Sherpa Prototype Adventure Bike

With the popularity of fat bikes at an all time high, the plethora of new tire/rim/suspension/frame options has allowed to designers and engineers to explore their wildest fantasies.

For Rocky Mountain, inspiration came from a set of over-sized prototype tires and rims from WTB, and the end result looks like the comically shreddable bastard child of a fat bike and adventure touring bike.

Jokes aside, this concept bike blends two incredibly different riding styles to create a seriously capable fat tire trail bike. Head past the break to learn more….

Rocky Sherpa and Prototype WTB 2.8 Trail boss tires

To create the new Sherpa, Rocky took a stock Element front triangle and stretched the rear triangle to fit the fatties.

WTB Trail boss Prototype

The prototype 2.8″ 650B WTB tires utilize the same tread pattern as the new Trail Boss, but add an extra bit of girth. They’re not quite as voluminous as proper fat bike rubber, but when paired with the extremely wide 45mm proto rim, they’re roughly the same outside (read: rolling) diameter as a 29″ tire.

Rocky Mountain SHerpa Loaded

Like a 29 + fat bike, the 27.5+ concept gives you the opportunity to use the bike in one configuration for traversing accross snow, sand, or the bike path. Swapping out the tires would give you the ability to setup your bike more aggressively come summer.

Rocky Mountain Sherpa Clearance

So there it is. The first 27.5+ full suspension trail fat bike I genuinely think looks rad (which is no small part due to Stacy Glasser’s incredible paint job!) and would love to rally. Want to see these products make it to the market eventually? Let WTB and Rocky know in the comments.


Kevin - 04/12/14 - 2:40pm

How is that a fat bike? It’s just a normal full sus with slightly wider tyres and a couple of revelate bags strapped on. That would last 4 days in the sticks before something broke. Nice tyres, but that most certainly ain’t a bikepacking or expedition bike.

Eric - 04/12/14 - 3:17pm

What part of this bike looks like it would last 4 days? looks high end and tough to me… I do agree its on the minimal side of a fatbike but they’re toting it as an all around shred machine not simply a snow bike. I say they give me one to test out on the colorado trail race this year to prove its durability? sweet thanks!

James S - 04/12/14 - 3:24pm

It’s interesting, but the proliferation of standards lately is mind boggling. Surly already started the 26+ (Instigator) and 29+ (Krampus, ECR) but before we even have more than a couple of tire choices in those sizes, here comes 27.5+. I kind of wish that WTB would have started with supporting one of those sizes instead of dropping another midfat wheel size into the mix.

So if WTB is really listening, I think if they are going to do a midfat tire, just go ahead and make it in all three wheel sizes please.

PS – I’m still mad at WTB for dropping the Dissent and Kodiak 29er tires so quickly. (My AM 29er rocks Maxxis Minions, thank Jeebus they finally made them in 29er size).

Vincent - 04/12/14 - 3:32pm

I love to ride my pair of WTB dissent too !
Please release them again with a folding bead for us alpine riders.

zemil - 04/12/14 - 3:50pm

love this idea. Have a pair of lightweight “skinny” 29er wheels for racing or general riding and 650b+ fat wheels for the snow or whatever. 2 for 1.

skipdapbaddamarangdoo - 04/12/14 - 3:57pm

This thing looks like a game changer for bikepacking to me. For Kevin I propose the question, where in your experience do you think you’d break something within 4 days on this? I toured around the Salt Lake(5 days/4 nights) last spring on a way lesser bike than this and it held up just fine. I also set up my Intense Tracer 2 with a similar component build to the Rocky and toured across the Unitas(3 days) on a mixed bag of gnarly single track, two track, and dirt roads with no issues. There’s a lot of terrain out there that could be tapped into with more ease and comfort with a war pig like this. Nice work Rocky!

Wasquatch - 04/12/14 - 4:25pm

Big fan of this bike, and bikes like it. I love gap bikes like this. I own gravel bikes, fat bikes, single speeds, and standard mountain and road bikes. I would be a buyer of this, especially with the paint scheme. Would love to do some bike packing on this versus a true fat bike.

Psi Squared - 04/12/14 - 6:06pm

It looks fun to me.

Willis24 - 04/12/14 - 8:36pm

+1 for zemil, awesome right!

Mindless - 04/13/14 - 2:43am

Nice. Me want.

Bigwheel - 04/13/14 - 2:15pm

Don’t miss the point here. This tire exists to allow those in need of/curious about 29+ to get with it for the price of a set of wheels and tires that they can slap on their existing 29″er, or at least a lot of them. No geo and negligible weight penalties, fits all a available sus fork etc.. Certainly a lot cheaper than springing for a + frame and kit.

Stu - 04/13/14 - 4:35pm

Nice. Almost there on the wheel size. A 29er+ is what I would love to try.

Michael Dachs - 04/13/14 - 5:17pm

This thing shows an almost comical amount of misunderstanding of what an adventure bike should be.

buriedundersnow - 04/13/14 - 8:20pm

Would be interested to see what the heel clearance is on the rear triangle. I have a tendency to clip my heels on some bikes…….Me likey though. The Dissent was a good tire…..

JS - 04/13/14 - 11:46pm

Love it. I hope this actually makes it to production.

puffy - 04/14/14 - 9:21am

Sweet, I’ll start stretching my rear triangle!

Kark - 04/14/14 - 3:24pm

@ Michael Dachs. I think you’re derision is unwarranted.
While it perhaps wouldn’t be the best choice for a trip over the Karakorum pass and thru Mongolia, it seems very well suited to long weekends or even weeks of lite touring along the Colorado Trail or similar adventures.

J - 04/14/14 - 5:46pm

The perfect solution/compromise… if it fits in standard 29″ frames.

Ham-planet - 04/14/14 - 7:53pm

This is the nicest expedition bike I’ve ever seen

@everyone bitching about ‘27.5″+’
They’re just slightly wider tyres on a wide rim in this case, Christ.

john - 04/17/14 - 7:42am

please put into production Rocky Mountain! love the ride!

Kris - 04/21/14 - 8:05pm

Looks great! Put it into production!

Pedro - 04/27/14 - 12:07am

Looks good and would love to have a pair of theese semifat wheels on a carbon xc 29er ht for training on rough tracks (alot of roots on the tracks whera I live) and would also us them during winter! Looks like they can swollow some pretty gnarly ground if run at low pressures and grip slimy roots alot better then 2.25*29 Ikons or RaRa’s that I normally use.
But will they fit in the rear of a “normal” xc 29er ht like a Giant xtc composite 29?

joshua bryant - 06/13/14 - 11:20pm

I’d love to see these hit the market. Well, the tires and the rims certainly. I think its a platform that deserves some resources.

Michael_S - 06/22/14 - 12:48pm

according to those who know the release date for the tires is Sept of this year. Some folks are already buying fat rims.

Blake - 07/22/14 - 5:20am

I’ve drawn up an approximate geometric comparison of 29er, 650B+, and full-fat tire/rim geometry, with the “rims” overlaid based on their relative diameters (622, 584, 559mm). This is based on Velocity Blunt 35 rims for 29er & 650B+ and a 65mm Marge for full-fat.

Looks like 650B+ with the 3.25″ Vee Rubber Trax Fatty should (hopefully) clear a 29er frame/fork, but it would be tight. BTW a couple of online retailers are quoting August 2014 ship dates for this tire.

cotterpin - 10/25/14 - 1:42pm

If it clears my Float fork and my chainstays, I would love to try a ‘plus’ sized tire! Getting a new bike is too much of a commitment for an unknown.

Post a comment:

Comment sections can be a beautiful source of knowledge, conversation and comedy. They can also get pretty ugly, which is why we've updated our Comments Policy. If your comment isn't showing up or suddenly disappears, you might want to check it out.