I'd listen to Tone. Stock 18" tires are supposed to be set at 29 p.s.i. (see back of owner's manual), but I was running them at 35 p.s.i. (not max, but close) and the ride was greatly improved. I am running my new 31" tires at their max rating (50 p.s.i.), so if I were you I'd look on the sidewall of your tires and go with whatever it says.