It will be smaller. It will even be smaller than a 26x3. A 650b is just about 1" larger than a 26" wheel (ignore the 27.5 marketing, it’s really 27), hence you only need a 1/2" larger tyre on the 26" to be the same diameter as a 650b.
It will be smaller. It will even be smaller than a 26x3. A 650b is just about 1" larger than a 26" wheel (ignore the 27.5 marketing, it’s really 27), hence you only need a 1/2" larger tyre on the 26" to be the same diameter as a 650b.