Originally Posted by
Tin_Man
According to that page 622 could still be 3 different sizes depending on where the tire is from!
I suggest looking at it from the other direction. A 622mm bead seat diameter is
always a 622mm bead seat diameter. There may be other notional/regional/fractional sizes in use by some parties, but going by the international standard (ISO) nomenclature will always get you to the correct place. A 55-622 will always be a ~55mm wide tire with a 622mm bead seat diameter.
I do think a 55mm tire on a 19mm internal width rim will work out fine -- especially a sturdy tire like a Schwalbe. I'd recommend keeping plenty of air in it...the wider you go without also widening the rim means the tire will want to "roll over" in corners. You want enough air pressure to support those forces as you lean into a corner.