I have an old 60s (I believe) Schwinn Suburban that has no tires. I looked up what size tires to get and found 27x 1 1/4 as the match. I just recently scored a set of 622x14 rims. Could I fit the 27x 1 1/4 tires on these rims?
No, not safely.
Bicycle tyre measurements are somewhat nonsensical, and plain unit conversions will not result in useful numbers - 27 1/4 inches is 692 mm which is larger than any common wheel rim.
27" and a fraction, is probably a ETRTO size of 630.
Aside, 27.anything " in a decimal is a separate system and cannot be rewritten as fractions while remaining the same tyre size. It really is a horrid mess.
The ETRTO number is a good attempt at standardising tyre sizes, and can be directly compared; that is any 622mm rim and tyre should work together, but 622 and 630 is different and won't. Easy.
Since you have bog-standard 622 rim, go with normal 622mm tyres which are available new. Even if your existing tyres fit on, they won't lock into the bead securely.
The other half of the question is whether your bike frame would take the 622mm rims - the front dropouts will likely fit, but the rear is probably a different width. And then there's the issue of making the brake pads reach the rim, and getting the chain to run on the cassette, shifting, etc.
Since you have the bike and wheels, it is probably less work to buy 27 1/4" tyres+tubes, and fit them to the existing wheels. The range will be small but they do exist.
Where I live, 630 tires and rims are extremely hard to get (and they are both expensive and low-quality), so I understand OP's goals here. The brake pads should be able to adjust some 3 mm lower. The frame is likely steel so cold setting it, or just chucking that 130mm axle in shouldn't present a big issue. I don't see a problem with the chainline and shifting, but even so, adjusting the rear mech is relatively trivial as far as bike maintenance goes. Aug 1, 2022 at 9:49
2That aside, they shouldn't have to find a tube specific to 27" rims, as a 622 tube should fit fine onto a 630 rim. Continental's 28" tubes have a print on them that explicitly says 622/630. I've done this with other inexpensive (3€) tubes as well. Aug 1, 2022 at 9:51