The 650B+ would give you something in between a normal 650B and a 29er and you might find that little extra for the climbing you're not getting right now and still gain the little extra room for your bits descending FYI a WTB TB on Flow rim measures 28.5" in diameter and an Ikon 2.35" on an i25 measures 29.25".
A mullet bike is a mountain bike with a 29 inch wheel at the front and a 27.5 inch wheel at the back. You benefit from the stability of the bigger wheel at the front and its ability to roll over roots and rocks. And the smaller 27.5 inch rear wheel brings the nimble and playful party attributes.A 27.5″ wheel can be installed on a 29″ bike. To minimize the negative changes to the geometry, it’s recommended to install two 27.5″ wheels. If you want/have to install only one wheel, it makes more sense to put it at the back while keeping the 29″ at the front. This will prevent an excessively steep head tube angle.
Consider using a fork with 10 mm less travel to reduce the geometry changes a bit. I’m running an NS eccentric 27.5 evo with a 120mm 29er pike , the axle to crown is within 2mm or so of a 140mm
27.5 tires are kind of 27.5", except the 27.5+ tires can be closer to 29". 27.5 are also called 650b because that's what the rim size was called before it became popular in the past few years in the mountain bike industry. It's actually a 584mm bead diameter. 650b used to be popular on small-frame road bikes that didn't fit 700c wheels very well.
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