Bro., if original size is 195/60R15, you can go down to 195/55R15, which is actually smaller already by 3.19% in overall diameter.My original size is 195/60 R15..
I've got friends suggesting to change to 50 series because there's more choices and the ride is better than 55 series..
You cannot use 195/50R15. It is too small and will look funny too. Diameter is smaller by 6.37%.
If 195/50 then must use 16" as in 195/50R16