Make sure you take into consideration the tire rating for Speedo % when putting them on the car - as well as the offset. Won't be as much of an issue for you as your a 4 bolt. But take a look at the tire size calculator to compare the tires you have now with the ones on the rims.
I never knew about this until I bought my G5 - I had the wrong size tires on the rims I had on my old car (I had the rims given to me with tires). So when I went into a shop after getting a spike stuck in one, I had to replace all 4. My speedo was WAY off with the other tires. I got a really good deal for 4 Z rated tires and then sold the car 3 wks later :haha