Some people may want to build a new bike and take advantage of existing wheelset on hand. That will bring a question: In case we have a 26" wheelset and 28" (700c) designed frameset, how will it work?
First let's take a look at the comparision of wheelset. From left to right：
28" (700c) Schwalbe Supreme 700-32c
27.5" Schwalbe Mondial 650b-2.0 / 584-50
26" Schwalbe Mondial 26" 2.0
We mesure the outer diameter：
26" / 27.5" / 28": 695mm / 690mm / 660mm
Obviously there's no much difference between 28" (700c) & 27.5" wheelsets. But 26" ones are quite different.
As a result, the distance from pedal to the ground will be decreased if wheelset change from 28" to 26". It will bring some risks when the pedals is at the lowest point. It will hit the ground under certain circumstances.
On the other hand, if we change 26" to 28" wheelset on a 26" designed frame, gravity will be higher than before, which will affect the steering and stand over height.
Moreover, 26" & 27.5" tires are wider than 28" ones. That is why more and more new 700c framesets accept 27.5 wheelsets also, just because the manufactory expand the tire clearence. Blacksnow is also following this new trend.
Thanks for reading. See you next time.