Hello, I bought an old bike on the cheap and would like to convert it to a single speed commuter bike. The serial number, N44955, appears to be a mid 50s Schwinn. The front spacing is 100mm and the rear is 135mm. The rear spacing is confusing me because Sheldon Browns website says that is common mountain bike spacing. The tires that came with the bike are steel Araya's, 27 1/4", the rear wheel has a JC Higgins 3 speed hub. I want to change to alloy rims because I live in a wet climate. I'm having trouble finding 27 1/4" wheels with 135mm spacing, most are 126mm. Do I have to stick with 27" wheels? Or could I switch to 26" wheels with 135mm spacing?