This website will help you with your decision where you can compare tire size.
Note: As a rule of thumb you shouldn't change the OEM circumference by more than 3%. And you will find a wider tire may cause interference/damage to the body or rub on the strut springs in a lot of cars, but our FX design has lots of room. And with a narrower tire you may feel your steering has a "lighter" feel, which you may like.
Note: Your 18" wheels are matched with a tire sidewall that is taller than my FX45 which has 20" wheels and small sidewalls. However, the circumference and diameter is almost identical. That said, a 20" wheel on an FX typically has a stiffer ride, but most people favor the larger wheel "look."
The best tire size calculator. Use our tire size calculator to find tire size specs and suggested tire sizes. Then check prices for all available tire sizes.
tiresize.com