Not sure what your Civic comes with stock, but with the stock Accord wheels, you'd have to change the total diameter by 2" to be off 10mph at 100mph.
If you switch the 195/65/15 for 225/40/17 you change your speed by 3mph at 100mph. Not a whole lot of cause to get the wigwags blaring, except for the going 100mph part.
Or maybe I'm just bad at math this late at night.
b