I agree with White_Knuckles. Which is why I went back to the 17". Luckily I only spent about $1,300 on the 20" with tires. They were Lexani tires. Inexpensive and good looking tread pattern. Again, not performance size or performance tires. Putting 20"s on a Bimmer is a self inflicted handicap. Shooting yourself in the foot - pin intended!
I've always felt that the 19" rear staggered with 18" on the front looks great - but unsure about what that does for performance.
As with anything on these cars, its a fine line between looks and performance. Im at the point now where I'm all about practicality, performance, and price. Hey, "3Ps"! That's mine everyone! Just made that up!