Originally Posted by
dabac
If ”need” be, 700C tubulars can fit on 630mm rims.
Rideable, but not overall a great solution.
People make that claim from time to time, but until I see a video of someone actually installing a tubular tire on a 630-mm (27") rim, or at least a photo supporting the claim, I'll remain dubious. Most tubulars require quite a bit of stretching (and sometimes cursing, in my experience) to fit on 700c tubular rims, let alone a 27" rim with raised sidewalls.
That said, some tubulars stretch considerably after being installed on a tubular rim and inflated, so maybe it's possible. If anyone can provide a video or photo demonstrating such a combination, please post it here.