For me, the solution is:
- 225/40/18 Front and 255/35/18 rear (Bridgestone RE11);
- Camber plates Vorshlag setting -2° front;
- Camber -2° rear;
- Sway bars H&R front and rear;
- Bilstein PSS10 (setting in 7 for street; 8-10 on the track).
With that, understeering almost nothing. Front feeling is very very good!
I do street and track days. I'm satisfacted with my 135i now!