One of the hot new mountain bikes trends is the 650B MTB. Its just another mountain bike wheel size. Bigger than 26" but smaller than a 29er. 650B mountain bike wheels are approx. 27.5" in diameter. It is also commonly referred to as the "tweener" wheel size. A lot of folks jumped on board the 29er wheel size a while back. But some mountain bikers, who may like the idea of a bigger wheel, and understand the clear advantages a bigger wheel brings, may not be totally stoked about the size of the big 29" hoops.
26" MTB is All but Dead
Most everyone is done with 26" wheels for mountain biking, but not all. The exception being just a few types of riders of course, like downhillers, dirtjumpers, and a few hardcore dudes with awesome 26" bikes they won't let go of. And comfort mountain bikes will likely keep rolling on 26ers. A new line of youth bikes from Jamis has adopted the 26" wheel. But, for the most part, the 26" mountain bike has given way to the 29er.
The 29er Reigns Supreme but...
29ers do have some clear advantages of which most mountain bikers are already well aware. 29" wheels have more traction, and once up to speed, its hard to slow them down. Its easier to maintain your momentum once you get going. Roots and rocks just do not slow you down because of that increased obstacle rollover. The 29er also has more bottom bracket drop, which lowers the center of gravity, making the 29er very stable. All of these things make the 29er pretty awesome. But, despite the clear advantages, 29" wheels are unwieldy for some short riders on smaller frames. Most mountain bikers like to be able to move the bike under them easily while carving up some trail, and 29ers are not very flickable. Those 29" monster hoops also do not jump well, they are harder to pump through sections of trail, harder to get around tight switchbacks, and they do not accelerate as quickly as 26" wheels did. So we have a dilemma, one wheel is too small, and the other might be too big.
Flickable is a term used by people to sound overly sophisticated when describing the handling of a mountain bike or motorcycle." For example, "A 26er has more flickability because all 29ers handle like dump trucks!" -Urban Dictionary 
650B is Just Right
So both wheel sizes, 26" and 29", have distinct advantages and disadvantages. What if there was a wheel right in the middle? Can a happy medium exist between too big, and too little? It only seems logical, right? The 650B, or 27.5, wheel size is promising to be the best of both worlds, or wheels, er, ...whatever, you get the point. 650B MTB has all the advantages of the big and little hoops, combined into one lovely wheel size. A wheel size that not only feels right, but also allows for more room in bicycle frames for tire clearances, front derailleurs, and more travel in full-suspension frames. These are great advantages in bicycle design.
So, 650B resides right in the middle of all. Promising good obstacle roll-over, good traction, better handling, more flickability, more forgiveness in frame design, and more choices for mountain bikers. Our opinion on this wheel size debate, is that every rider needs to make up their own mind. Listen to all the hype, and then test ride some bikes. Try the 29er, and then try the 650B, and see what feels better to you. It seems taller riders like the 29ers and shorter riders like the 650B. So, height is a consideration, but not the only one. Your choice should also influenced by the terrain you plan to ride the most. If you're just want to roll gravel roads or ride long XC routes, a twentyniner might be best. If you want to pump through sections of trail, catch air wherever you can, and you value maneuverability above obstacle rollover, then a 650B might be best. Personally, I am 6' tall, and I like both wheel sizes. But, my choice of terrain determines the bike I ride. Rothrock is a great place to ride, but its rocky, and I prefer the 29er hardtail over a 650B hardtail out there. If the 650B is full-suspension with 130mm front and rear, well then that changes my decision significantly. A 650B dualie is a pretty formidable weapon on any trail. Its maneuverable, its plush, it jumps, it carves, it is awesome. On a 650B MTB with full suspension the small decrease in obstacle rollover is alleviated the the rear travel.
Jamis Bikes has a Big Headstart
So, if you are looking to try out a 650B mountain bike, come see us and try out a Jamis! www.jamisbikes.com
And now, a look at the future... the 650 plus adventure mountain bike... the Dragonslayer.
650B wheels with 3" wide tires.
