Functional bikes. Not Porn not Anti

Anyone know if going 650b on a Kaffenback is doable?

Going 65ob is doable on any road bicycles with disc brakes (moreso than rims brakes), however your main concern is merely the chainstay clearance and sometime the fork, for example, if your chainstay simple spread out evenly like this, then you can fit bigger tyres, says 32mm, 38mm or even 42mm;

If your chainstay is more like this where it get narrower halfway before spreading out (for "comfort" and "compliance" apparently), then you may not be able to go as big as you can, and need to be measured carefully;

After I have ridden the Cannondale Slate with 650b 40mm Schwable G-One tyres, I'm now convicted that I should convert my Saracen Avro, a disc thru-axles road race bike whose chainstay traditionally curve out, currently it got clearance for 32mm tyres, so 42mm Grand Bois Hetres with lightweight MTB 650b wheels (1300-1400g maybe) is 100% possible;