some lowering springs would be good to get

Didn't want to start a newbie thread for this, but why do people go with 35 sidewall on the rear tires on 17inch rims? Wouldn't you want 315/45/17 to keep your speedometer accurate? I see 255/45/17 on the front and 315/35/17 on the rear in peoples modlist all the time, this just seems odd to me, smaller diameter wheels on the back...
The middle number is a percentage of the width. So the side wall is 35% of the width of the tire on a 315/35/17. A 245/45/17 is the same height as 315/15/17.

Wow did not know that. I always thought the middle number was the sidewall measurement
Sweet, so the 103.25mm sidewall vs. stock 110.25mm isn't that big of a difference at all then?
If so I'm going with 255/40/18 up front and 295/35/18. After much number crunching this should give me a perfect tire size for 18x9 up front and 18x10.5 in the rear. About a half inch overhang on each side of each tire.