here it is again
Dec 24, 2016
26" Tire sizes by Diameter...
S-2 ........... 559 mm (26 x 2.125 / 1.75) Balloon , mountain and middleweight
S-7 ............ 571 mm (26 x 1 3/4 ) Schwinn Middleweight
S-4 ............ 584 mm (26 x 1 1/2 ) 650b / Schwinn Welterweight AND todays new 27.5 tire designation
EA-3 ......... 590 mm (26 x 1 3/8) Lightweight
S-5 / S-6... 597 mm (26 x 1 1/4 - 1 3/8) Schwinn Lightweight (AKA as EA-1)
S5 was intended for 1 3/8" wide tires ( available in 20" 24" and 26" )
S6 was intended for 1 1/4" wide tires ( available in 20" 24" 26" and 27" )