Finally got my new 18"x8" Lexus GS430 wheels mounted up this morning with BF-Goodrich g-Force T/A KDWS tires 235/50ZR18. I went with the slightly larger tire size in order to correct for my 5% speedometer error. These tires will correct by 4.2%, so my speedometer should now read correctly. However, my odometer will also go further off from the existing 1.5% (assumed to be same as WVGasGuy findings via GPS) by another 4.2%, so I will not be able to use the TCH display for fuel mileage.
The car looks so much better with these wheels and tires! Definitely does not look like your basic family sedan anymore. Still not as sporty as an SE due to lack of body kit, but that will be my next project. I no longer have a desire to drop the car anymore on TRD springs, because the 50-profile tires filled up some the gap in the wheel well. In fact, 235/50/18 is probably the most you can go, because I only have about 1/4" left before the tire would rub the spring cover (see picture). The wheels and tires also stick out a little more, they still don't protrude past the wheel well.
Here are some Before/After pics, as well as a closeup of how close I am to the spring cover. I'm loving thse wheels, but I'm obviously biased. Let me know what you think!
