Heather Clark / The Bulletin

In the lexicon of mountain bikers, terms like singlespeed, dual suspension, hardtail, fully rigid and travel (as in, “I have five inches of rear-suspension travel”) are common these days.

Into that jargon has crept a relatively new term, one that may have some riders new to the mountain bike scene scratching their heads.

A twenty-what? Niner? What in the name of knobby tires is that?

A 29er (which often appears as simply “niner”) refers to a mountain bike with wider-diameter rims. Standard mountain bike rims are approximately 26 inches in diameter. Twenty-niner mountain bikes have — you guessed it — 29-inch rims.

So how much difference do those 3 inches make?

“It’s like cheating,” says Bend’s Lawrence Fisher, 36, quoting the comment his wife Melanie said after her first ride on a 29er. “She went and rode on the trails, and she’s like, ‘Holy crap. I rode down a trail I have never been able to do and it’s so easy.’ ”

The “cheating,” so to speak, is a product of the surface area — or footprint — of the 29er tires. More rubber means the tires can adhere to more of the trail or obstacle.

“The benefits of the 29ers are that they roll over things such as roots and rocks better than smaller wheels,” says Kevin Gorman, co-owner of WebCyclery, a Bend shop that specializes in sales of 29er mountain bikes. “Think of a monster truck driving over cars. (Twenty-niners) make for a smoother ride and more comfort, and they have a bigger contact patch with the ground and therefore offer better traction.”

Twenty-niners appeared on the national mountain bike scene in the early 2000s.

The wheels were first embraced by small custom-bike builders. But as more and more consumers began seeking them out, the major mountain bike manufacturers also got on board. Today, nearly every major mountain bike manufacturer produces a 29er.

One California company, Niner, manufacturers the big-wheeled bikes exclusively. According to a San Fernando Business Journal story, Niner’s sales revenue catapulted from $658,356 in 2007 to nearly $6 million in 2010. And Niner founder Chris Sugai told me last week that industry statistics show that 29ers are now the majority of mountain bikes sold in the U.S.

Gorman says his Bend shop began selling 29er tires and wheels in 2004. By 2005, the majority of WebCyclery’s tire sales were 29ers.

Today, sales of 29er bikes, parts and accessories far outnumber those of 26-inch stuff, he says.

In search of a bike that would fit his tall frame, Bend’s Jason Meyer bought his first 29er in 2005. The 6-foot-6 inch rider had difficulty fitting on a standard 26-inch mountain bike.

“It was a little clownish because the frame was so big and the wheels were so small,” Meyer recalls. “(The 29er) was more proportionate for me.”

The 35-year-old athletic trainer and part-time guide for Bend’s Cog Wild Mountain Bike Tours is now on his third 29er.

In addition to rolling through tricky rock outcroppings with ease, the tires on a 29er maintain speed with less effort than their smaller counterpart. This, however, is both a plus and a minus.

“It takes more effort to get the wheels moving, but once they’re moving they stay moving longer,” says Meyer.

But 29ers do have their drawbacks — and their critics.

“Everybody has their own style and that’s what it comes down to,” says Meyer. “There’s a learning curve when it comes to transitioning from a 26- to a 29-inch-wheel bike. The biggest part is accepting the fact that you have to get a bigger wheel rolling. When I slow down, I’ve got to get these wheels rolling again and some people don’t like that.

“It took me probably a good year to figure it out that you have to read terrain a little more and keep your legs spinning and the momentum going so you don’t have to start the wheels from a stop.”

Fisher, a longtime mountain biker whose quiver of dirt rides includes both a full-suspension 29er and a 6-inch travel bike with standard wheels, opts for his traditional mountain bike on tight, narrow trails, which require a snappy performance from his bike.

“(On a 29er), when you’re going up technical terrain it’s easier to roll over stuff,” Fisher says. “When you’re going downhill — because of the bigger wheels — it’s harder to ‘endo’ the bike. There’s less of a chance of feeling like you’re going to go over the handlebars with the bigger wheels.

He adds: “A 29er isn’t going to maneuver as quickly in tight turns. The bigger wheel is harder to make it through that stuff.”

Ina McLean, a 5-foot-5 inch mountain biker, says 29ers aren’t just for the vertically endowed, though it took the 52-year-old Bend resident time to adjust to the change.

“It was a little hard to get used to at first — it’s bulky insofar as you’ve got these big tires all around you,” she says. “At first I thought, ‘Oh my gosh, I’m riding a tank.’ ”

McLean opts for her standard mountain bike when she’s planning to ride twisty, handle-bar-wide singletrack, such as Sector 16 or the curvaceous, jump-riddled Whoops Trail in the Phil’s Trail network.

“Most everywhere else it’s really fun,” McLean says. “It just goes over everything.”

A series of tire-jilting rock gardens on the COD Trail in the Phil’s system have made pinballs out of many a mountain biker, including McLean, until she tackled it with her 29er.

“I’ve always bobbled at least one part of it,” McLean says. “But the first time I went on my niner I thought, ‘Wow, that was easy.’ ”

Meyer says riding a 29er gave him more confidence.

“People think that 29ers are slower in tight terrain, and that’s an arguable point for sure,” Meyer says. “But if you’re riding down Phil’s Canyon or the south side of Storm King, you can just rip.

Adds Meyer: “It’s all about keeping that momentum.”