650B Wheels?

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The 650B wheel is a revolutionary innovation sweeping through mountain biking. Here are some key facts concerning 650B wheels:

  • They are round
  • You put rubber tires on them, and pump them up with air
  • If you’ve had better things to do than read bike magazines lately, 650B is a wheel size that’s 25mm larger in diameter than a 26” wheel and 38mm smaller than a 700c or 29” wheel

650B has gotten a lot of hype lately and we’ve had a lot of people asking about it in the shop.  There’s nothing terribly right or wrong with any mountain bike wheel size, provided the application is correct. The truth is things like tires, suspension setup, and chassis geometry have a much larger role in how a bike rides and handles than wheel size does. A larger wheel does have a small advantage in traction and rolling resistance, especially over rough trails, but a smaller-wheeled bike could still be better if it had better suspension. So which wheel size should you choose? In a perfect world, a bike would be designed around the best geometry and suspension for a particular rider. Suspension travel, axle path, head tube angle, trail, chainstay length, seat tube angle, etc would all be chosen based on that rider and the trails they ride. With that settled, the bike’s designer would use the largest wheel that would fit into those parameters (taking front end trail and BB height into account of course). In this dream world, stock bikes of different sizes would come with different wheel diameters and corresponding chainstay lengths. Currently, most mountain bikes use the same chainstay length for all sizes, even though the difference in effective top tubes from XS to XL can be as much as 10cm. Think every size has the same handling characteristics? Not a chance! In our ideal bicycle world, hardtails and shorter-travel dual-suspension bikes would trend toward larger wheels, since their frame designs allow bigger wheels to fit, while longer-travel bikes would trend toward smaller wheels to accommodate their suspension designs without stretching their back ends out too far. Will this dream world where everything makes sense ever materialize? I doubt it. But when I’m out in the woods riding my mountain bike, I can always dream…