Originally Posted by Vic311
Wider tire equals more grip, but the downside is that the tire/wheel combo will be heavier which means a lazier handling "feel"
Overall the PSS is a better tire than the Hankook
much more important than the minute difference in weight from the tires is having the proper width wheel for a given tire size.
you will notice that BMW likes to use stretched tire / wheel fitments. the stretch allows the wheel to provide some extra sidewall stiffness that helps with steering feel and cornering stability
the right tire size depends on your wheel widths.
on topic, the v12 is a low quality tire that cannot keep up with a high powered car that already has traction issues with higher quality tires like the m3. the soft sidewall will also introduce more roll and slop into your cornering and steering feel.
spend more for better tires is my advice.
EDIT : seeing that you have 9.5/10.5 wheels, 265/35 and 285/35 is proper fitment and will have approximately the same amount of stretch as the OEM wheels did on 245/265.