With 18's I run 30psi front and 37psi rear. The dealer put a couple extra pounds in each when I was in a couple of weeks ago and it felt really rough... like someone had mounted tractor tires or something. I lowered the pressure back to specs (30/37 is what my door sticker says for 18's)... and now the ride is good again. I didn't realize the PS-2 tires were so apparently sensitive to pressure.