Joined: Jan 2009
Posts: 44,320
Likes: 6,605
From: New York, NY, and High Falls, NY, USA
Bikes: 1962 Rudge Sports, 1971 Raleigh Super Course, 1971 Raleigh Pro Track, 1974 Raleigh International, 1975 Viscount Fixie, 1982 McLean, 1996 Lemond (Ti), 2002 Burley Zydeco tandem
Perhaps the 1-1/8" marking means that's the approximate inflated width on whatever rim they expect you to use. The ETRTO size (23-630) is measured a specific way. They didn't measure the actual inflated width. They measured the linear distance between the beads of the tire (when flattened out) and divided by 2.5.