I agree with Wildwood. Just get the fattest tires that will go on the bike. Unless you weigh less than 100 lbs, 23mm tires are ridiculous and 25mm will still be a hard ride. I weigh 185 and have either 32 or 28 mm tires on my road bike. Wider = more comfortable, lower rolling resistance, better grip in the corners, fewer pinch flats. Win, win, win, win. The only advantage to skinny tires is weight and in some cases aero (which is irrelevant at speeds under 20 mph).