During the 28" to 26" wheel transition period starting in 1933 through I believe 37, some motobike frame makers (not all) simply used the old 28" frame dimensions for both wheel sizes and some did not, depending on whether the stay width would take a wider 26" tire. Those that did simply used a fender spacer on the seat and chain stay bridges while using a shorter & wider-crowned fork. Early Snyder-made Hawthorne's I know did this and maybe others . Not sure if Schwinn did so. Colson, in late 33 straight away shortened both the chain-stay AND fork width/length(moto frames) when the 26" size came on the scene. It would be interesting to know when Schwinn made frames and forks specific to 26" with wider fork crowns/shorter lengths and where in the serial number base this ended /began.