The main thing to keep in mind when switching from RFT to non RFT... is that the non RFT will have less turn-in feel. Meaning the slip angles feel greater or the steering is ever so slightly LESS responsive when you first turn the wheel. BUT that is the only negative when comparing RFT to Non-RFT's. In every other category - regular tires perform better. Far better if you ask most 1Addicts.
It is also important to pick out a Ultra-High performance tire and not your average performing tire. This is why I choose to go with Michelin PS3's(or PSS's). Tires are the only thing that connects your car with the road. It is best not to skimp on tires.
One thing with "low rolling resistance eco tire's" is that they have LONG braking distances than normal tires. And much less than Ultra-HP tires. Also... they tend not to corner as well as "normal" tires(non eco).
Another important thing to consider is to choose a tire that has an XL rated sidewall... these tires can carry more sidewall load and are built with a stiffer side wall. This will help reduce the difference in turn-in response when switching from RFT to non RFT's.
And one last thing... IF your gonna stick with RFT's... make sure the RFT's have a STAR logo on the sidewall. This means that tire has been made for BMW cars with RFT's. The RFT's that do not have this star tend to ride much harder bc they are not tuned for BMW's. I have this problem with my (17")snow tires - they are RFT's but without the star logo(none were available when I needed snows). They ride rougher than my old RFT 18's summers.
Here is my review when switching from factory RFT's to non RFT's.
My new Michelin PS3’s 225’s & 255’s…
http://www.1addicts.com/forums/showt...chelin+PS3%27s