Why 18's over 19's for better handling?
I don't understand why the 18's would handle better than 19's.
The 19"s have a lower profile sidewall to keep the tire from rolling too much during hard cornering, thereby keeping more tire to the ground. The lower profile makes the car feel more stable and planted with less roll.
I don't get why a 40's series tires is even offered on the M.
Look at all the Ferraris, Porsches, Lambo's, Corvettes, they are using anything from 35 down to 25 series.
They ONLY reason I can see is weight. If you take the weight out of the equation, I would think a 35" 19" would corner better that a 40" 18"
16' M3 Mineral Gray, DCT, Adaptive M sus., 19" wheels
15' Audi S4
13' Audi TTRS (APR stage 1, MSS springs)
09' C6 Z06
08' M3 Interlagos Blue: 6sp, Tech. & Premium Package