Generally something which doesn't extend past the rim width, so I'd probably go with 23s, which are going to come up a bit wider than 23mm (assuming they are actually 23mm on the old default 20mm rim) and will roll like 25s.
@gbj_tester started
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Generally something which doesn't extend past the rim width, so I'd probably go with 23s, which are going to come up a bit wider than 23mm (assuming they are actually 23mm on the old default 20mm rim) and will roll like 25s.