[Chrakaknox]

I'm curious as to why the stock 18" setup (225/45/18) is approx. 26" in diameter, and the optional m-sport 19" setup (225/35/19) is approx. 25" in diameter? How much of a difference does that really make? Why wouldn't, on the other hand, the 19" setup match the 26" diameter with say..225/40/19? I'm trying to understand if it matters much. I'm contemplating getting new rims when I get mine in a few weeks, and I've even read that smaller diameter tires change the overall axle ratio to get better acceleration becuase its a smaller diameter to turn? Can anyone help me out with this? thanks in advance, I've learned a lot on this forum already....