Pacenti introducing 650B MTB tires

Mountain bikes were rolling along nicely on 26-inch wheels, then 29. Now Kirk Pacenti wants to introduce the 27.5-inch standard, which some say makes good sense.

Mountain bike wheel and tire standards have centered around the 26-inch (559mm rim diameter) platform, until Wes Willits and Gary Fisher brought 29-inch (622mm) to market nearly 10 years ago. Better rolling, they said, and by the looks of the current 29er movement, they’re onto something. Kirk Pacenti believes in another size, known as 650B (584mm), for many legitimate reasons. Heaven help us!


According to Pacenti, the 650B size for off-road use has plenty to get excited about:

* With 650B wheels (which measure 27.5″ in diameter, half-way between 26- and 29-inch wheels), full-suspension bikes can be produced with four to six inches of travel and throughout a wide range of frame sizes without abandoning proven 26-inch wheel frame geometry.

* 650B wheel bikes can be designed for a wide variety of uses from XC racing to 4X and DH racing.

* 650B wheel bikes can accommodate riders 5′ 3″ to 6′ 4″ tall or more.

* 650B wheels offer great obstacle roll-over capabilities for a smoother ride.

* Consumers are already demanding 650B bikes and bike designers are producing the bikes.

“What I believe 650B wheeled mountain bikes will allow builders to do, is to utilize proven 26-inch wheeled geometries, coupled with the largest wheel possible in a bike with little or no geometry compromises,” Pacenti said. “As 140mm travel bikes become the norm (even for XC bikes) the 650B wheel size is going to make even more sense.”

Hard to argue with Pacenti, but what about the effort it’ll take to get the big tire makers on board? Pacenti has already covered that rocky ground. A Pacenti-designed and branded Panaracer-made 650B tire – the Neo-Moto – is currently in production and will be available by mid-September for $54.95US each. Current handmade samples weigh approximately 740g, according to Pacenti. In addition, White Brothers is producing suspension forks for the new wheel size, and Velocity USA, which has built 650B rims for the bicycle touring market for years, is already in production of their new Blunt, all-mountain MTB rim.

Because the 650B wheel size is compatible with many 26-inch wheel components numerous parts are already available. For instance, Maverick forks can be easily optimized for 650B wheels with a travel reduction kit, and some current 26-inch and all current 29-inch disk specific suspension forks will work with the 650B wheel size.

“The 650B wheel size makes more sense for a company looking to produce big wheeled bikes in the 100 – 150mm travel category”

“Kirk’s forward thinking vision is correct in that 29’er wheels don’t work well for frames with more than 100mm of rear travel,” adds Noel Buckley of Knolly Bikes. “While working on the design of a 29er version of our new Endorphin frame, we started realizing that serious compromises would need to be made to the frame geometry due to undesirable forward wheel paths, chain stay lengths, and BB height all caused by the large 29” wheel diameter.

“Kirk knows what he’s talking about,” Buckley added. “The 650B wheel size makes more sense for a company looking to produce big wheeled bikes in the 100 – 150mm travel category because they get the rolling benefits of the larger tire, but don’t have to modify frame geometries much, or have to contend with the design compromises imposed by 29 inch wheels.”

As many as a dozen manufacturers will have 650B parts and components ready for this year’s Interbike trade show and distribution of the new Pacenti 650B tires will be handled by a number of well-known distributors. (A list of distributors will be available soon.)

“I am fully committed to the 650B wheel mountain bike,” says Pacenti. “I have been receiving daily inquiries from custom builders and even consumers who are very interested in the wheel size. Support for this project has been overwhelming. I truly believe 650B wheel bikes have a bright future in mountain biking.”

Pacenti’s 650B for-the-dirt evangelism is catching on. Numerous independent bike designers are fully embracing the new 650B wheel size and producing 650B frames. There are even some bigger players testing out the concept. The current list includes: