I'm putting together some ideas for my second build, i have a Schwinn Speedster from approx 1966 with a 3 speed Sturmey. I don't know if these are S5 S7 or S? rims. In fact I just learned about the S rims today. I would like to put some 26x2.125 fat tires with prewar tread on them from fleabay, but now i'm questioning whether they would fit. Any help with that would be greatly appreciated. The forks and frame will be heavily modified, so i'm not worried about it fitting the bike, just the rims. Build #1, still running strong. May need to sell it to fund build #2, we'll see how that goes.