Originally Posted by systemBuilder

Until the latter half of the 1970's (1976-onwards, roughly), you could NOT get 27 1 1/8 tires. They had not been invented yet! The new narrow tires were a 2nd-half-of-1970's thing, perhaps an attempt to respond to 700c rims which offered the tubular tire experience and swap-ability with tubular rims for race day. In 1977 I was in high school and bought a SEKAI 2500 with 27x1 1/8 tires, and the narrow wired-on tires were a big selling point, only 290 grams, and the 27x1 tires which sekai/(probably panaracer or national) offered on the SEKAI 2700 were even lighter, at 270 grams: https://people.ece.ubc.ca/~gillies/s..._gt_deluxe.jpg

Up until 1977 I rode a Raleigh Gran Prix with 27x1 1/4 tires, the only thing you could get in terms of tires.