pushVTEC said:215/35/18 : Speedometer reading with non-stock tire is 3.1% too slow. When your speedo reads 60 mph you are actually traveling 61.8 mph.
205/40/17: 1.1% to slow. When your speedo reads 60mph you are actually going 60.6 mph
215/30/18: lowest i could get was 30, but the results were it being .6 too fast when your speedo read 60 mph you are actually traveling 59.7mph