My son's '82 Raleigh has Araya alloy rims that say 27 X 1 1/4 on them. I'm changing the rim tape and started wondering whether the rim itself would fit a 27 x 1 1/8" tire. The rough measurements are 2 cm outside to outside on the rim and the inner measurement is roughly 1 cm. On the inner portion of the rim there are two numbers repeated three times 23 and 13 (with something in between but always hidden by a spoke end).
I'd love to get a little more pressure in the tires for him and the slightly narrower 1 X 1 1/8 might work but I don't know if it would seat properly on the rim.