I have this wide touring rim and wonder if a 25C tire would fit. I don't want to damage the rim. It appears on the Sheldon site that it would work but would be the bare minimum. From what I understand the continental runs a bit larger.
I'm running Pana Racer 35C tires and they feel lumpy.
Don't think there's any such thing as a "25C" tire (I presume you mean 25 mm), but I currently have a 23 mm wide tire on the front of my touring bike which has an 18 mm internal width rim (Sun CR-18). Seems to be working fine.
I have some 622x17 rims and I once tried to put some 700x25C tires on them. The tires actually measured closer to 23mm width and they would not stay on. The tire/rim combo was a very loose fit to begin with and the tire kept popping off the rim when I would get the pressure up to about 80psi.