Complete guide to wheelsizes: 26in, 650b, 650b+, 29in, 29in+

Alan Muldoon

There are now a baffling five different wheel sizes being offered across the mountain bike market. So how do they size up?

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Just when you thought the wheelsize debate had settled down, along come two new ‘Plus’ standards. By using wider rims and big, fat 3.0in tyres the mountain bike industry has reinvented the wheel once again. So in addition to 26in, 650b (27.5in) and 29in, we now have 650b Plus and 29in Plus.

Given that 29er Plus bikes are essentially mini fatbikes, they will probably have a niche following. 650b Plus, however, is going to hit harder than a tsunami when brands launch their 2016 bikes.
Genesis are leading the charge, but big brands like Specialized and Trek aren’t far behind.

Another plus is you’ll be able to fit regular 29in wheels on 650b Plus bikes, giving you the choice of extra comfort or increased rolling speed.

While 650b+ and 29in share the same outside diameter – so should keep geometry stable – it’s unlikely many current 29ers will be able to accomodate the extra girth of the 3in tyres.

Here are the vital stats:

26in (26×2.3in tyre)

  • Bead Seat Diameter: 559mm
  • Outside Diameter: 677mm

27.5in (650b) (27.5×2.3in)

  • Bead seat diameter: 584mm
  • Outside diameter: 702mm

27.5in+ (650b+) (27.5x3in)

  • Bead seat diameter: 584mm
  • Outside diameter: 740mm

29in (29×2.3in)

  • Bead seat diameter: 622mm
  • Outside diameter: 740mm

29in+ (29x3in)

  • Bead seat diameter: 622mm
  • Outside diameter: 778mm