S-7 Schwinn rims are a tiny bit larger in diameter, so you must use an S-7 tire. I can't find any wide ones, only 26 x 2 x 1 3/4. That tire will be too big for a standard wheel. A regular tire looks like it will fit, but it won't, it will be a tiny bit too small. The narrow tires are the same way, S-5 or S-6 I forget which. Schwinn S-2 rims will take a standard tire. My Dad used to cuss up a storm when the tires wouldn't fit.