Amid all the excitement about fat bikes–mountain bikes with 4″ or wider tires–a few companies have started to push frames that can accommodate fatter-than-normal but not-quite-fat tires. Some call it mid-fat, others simply add a plus (+); for now, the consensus seems to be that “plus” means a 3″ tire and 50 or 52mm rims*. Here’s a round-up of all the plus size mountain bikes on display at Interbike for those who want a little extra tire width without going fat bike crazy.

Chumba Ursa

2014-09-22 chumba_ursa1

I got a chance to demo this bike, and it was a solid ride (read my full review here). The Ursa rolls on Maxxis Chronicle tires, one of only a couple 29+ tire choices right now (the Surly Dirt Wizard and Knard also come to mind.)

Surly Krampus


The Krampus was the first mass-market 29+ mountain bike and Greg got a chance to test ride one at Interbike two years ago. The company categorizes this as a trail bike, though I wouldn’t go that far. It’s a fun and aggressive bike but I’d personally feel a lot better about going fast if the bike had a suspension fork.

Surly ECR


This year at the Surly booth we spotted yet another Surly 29+ offering: the ECR. Surly describes it as “something of a lovechild borne of our Krampus, Ogre and Long Haul Trucker.” Whereas the Krampus is built for normal trail riding, the vision behind the ECR is touring / bikepacking. Designed to run either a full drivetrain, singlespeed, or internally geared rear hub, the choice of which system is the most reliable is up to you. The ECR features a variety of rack and bottle mounts, with bosses all over the frame and fork to accommodate just about every conceivable combination, along with a Jones loop handlebar for mounting bar bags and other goodies.

I can hear what you’re thinking: “isn’t this just a Krampus with a different build kit?” Actually, it isn’t: while the frame geometry is close to the Krampus’s, it’s been tweaked and optimized for long distance riding, making this a completely unique frame. Check out full geometry details here-Greg Heil

Niner ROS 9 Plus


Niner wasn’t quite ready to demo the ROS 9 Plus at Interbike, but we at least got to see one in person and it looks pretty sweet.

Jones Plus

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While we didn’t get a chance to meet with Jeff Jones at Interbike, he was in attendance with his new 29+ rig, the Jones Plus. The unique Jones Truss Fork can accommodate 29, 29+, and 26×4.8″ tires (although no word on what the possible benefit of running a 5″ front tire with a 3″ rear tire is). For more information, check out the Jones Bikes website-Greg Heil

Other “plus” news

WTB showed off their 27.5+ tire and rim at Interbike, though we still don’t have a bike to put them on unless you count the FS 27.5+ concept bike Rocky Mountain showed at Sea Otter earlier this year. It’s just a matter of time though: Stan’s is offering their 52mm Hugo rims in 26, 27.5, and 29″ diameters.


There’s still no 29+ suspension fork, though we’ve seen examples of folks using both RockShox Bluto and RS-1 forks (even the Pike will reportedly work). But once a true 29+ suspension fork is available, expect to see full suspension “plus” rigs rolling out.

* Surly calls the Instigator a 26+ mountain bike since it uses a 50mm rim, though the tires are not quite 3″ (they’re 2.75″).

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