Originally Posted by
Graham Wallace
The availability of wide 28" tires depended on where in the world you lived and how wide a tire you wanted. In Finnland they used heavily treaded 700x47C (28x1.75" or 47-622 ISO) and 700x44B (44-635 ISO) snow tires on roadster bicycles. In Europe there where also some 700C x 52mm balloon tires. Though these were lightly treaded road tires.
You also can buy fat tires (26x4 or even 4.8) with smooth profile. Not sure why, but they exist. Any tread can be on any tire width, it is just limited by demand to make it profitable since tires need to be produced in an expensive factory with very expensive molds.