The frame style was changed just after the 1995 models when Schwinn became part of another company (which is why Huffys look about the same). The 'original' design dates back to the mid-30s, with a number of changes and the new frame only looks similar. SAE/English parts and metric sizes were already mixed by the time the 1995 Centennial line came out. There are even differences in wheels and tires sizes as Schwinn had used it's own rim sizing system. Middle and lightweight rims on older Schwinns were not interchangeable with other brands necessarily, i.e. none of my Rollfasts, Western Flyers or the J. C. Higgins project I used to be working on could use Schwinn wheels and vice versa. The Schwinn S-2? wheelset is too wide an axle.
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I don't know nothing, and I memorized it in school and got this here paper I'm proud of to show it.