Run a few options through the calculator on
this page (look for "A tyre size calculator" a bit more than half way down the page). If I were you I'd punch in the original 195-55-16 size on the current side. Looks like going to 195-45 will have quite an effect on your speedo and odometer readings. On the other hand, the smaller overall diameter and circumference will improve the gearing for acceleration (and reduce your top speed). I know people who have gone with even smaller diameters for just that reason but remember the look and wheel gap will change as you go smaller. For example, the difference in
radius from 195-55 to 205-50 is a reduction of about one centimeter while 195-55 to 195-45 is a reduction of almost twice that.
If it was me, I think I would consider some spacers and another set of 205-50...or maybe 205-45 if they make them...maybe.
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FYI. I've posted links to the Tyre Bible site before. To anyone who had followed those links: the guy rearranged his site and moved things around so those old links (if you saved them) may not work anymore.