[mikesee]

I think the difference is about 1.5", give or take, from 26" to 27.5". And then another 1.5", again give or take, from 27.5" to 29".

Or you could just shortcut it and say the difference is 3" from 26" to 29".

There you have it--'the maths' at work.

 

[mikesee]

Wrong mikesee

559 (26) or 22" rim diameter
584 (650b, 27.5) or 23" rim diameter
622 (700c, 29) or ~24.5" rim diameter

622-584=38mm
584-559=25mm

So the '27.5' wheel size is not halfway between 26 and 29
Read more on Sheldon Browns website

So you're riding around on rims, sans tires then?

Neat. Your LBS must love you.