Fun flats as i like to call them dont have as much grip. Thats what i feel. Im no expert but a stiffer sidewall may be the reason.
My car on the track was significantly better with some hankook v12s.
I just switched out the summer funflats on the 135i as well and i like them more already as well. The oems were too hard and even cracked a tpms.
Monkey see monkey do...I drive a poseur modified sedan.