Getting some new tires...

today i was planning on going on a nice back road drive up from NH to ME with my girlfriend and at the gas station i noticed that i had a nail in the tire. i thought i could ride it out until i got home but no. long story short, i had the car towed on a flat bed to a local tire shop where he gave me a set of dunlop 275/40s for the ride home. satruday im going in and he's changing all 4. my front two were ok, but the rear two were **** so i figure just change all of them at once.


im gettting the michelin ps2 s all around. 225/40- 18 in the front and 265/40-18 in the rear.

i had the p zeros of the same size on the car now. did i make a good choice with the PS2s?

i have a question though, on the passenger side door jam, it said that the original tires were 155/40-17 in the front and 275/40-17, but the wheels on the car are clearly 18s. am i missing something here?