Originally Posted by
Kai Winters
Generally 1.5" maybe a bit more...depends on what will fit in the fork and rear stays...also smoother tires would be better than a knobby tire...the 'knobs' tend to make the tire wider than it really is.
I generally always use a 1.5" up to 1.75" tire in the shop when replacing tires on the size wheel you mention.
27.5 is the newer name for 650B and has the same 584-mm bead seat diameter. 27.5 rims can fit the tires you mentioned. The OP has 27 x 1 1/4" wheels: 630 BSD.