[LarThaL]

This is the achilles heel of the M3. It needs wider rubber at baseline, even in stock form. However, even there there are compromises.

Wider tires will give better traction but will also increase weight, rolling noise, and diminish steering feel/responsiveness slightly. If you increase width on only the rear, you will have to accept slightly more understeer.

All said, however, I think the M3 should have 245/285 as stock sizes. Too bad that the best street tire out there, the Michelin PSS, doesn't come in the needed 285/30 size.

This is why I have to laugh a little when I think about the M5.... a front engine RWD car putting down over 500lb-ft to just the rear wheel on tires that are puny for the car/power. You can break traction until about 100mph. What is the point of all that power if you just can't get it to the ground? This of course, makes the case for AWD, however, in that configuration, steering feel and responsiveness is definitely reduced. Only cars with rear and mid-engine designs have been able to produce AWD cars while retaining real precision steering feel. The one noted exception is the Porsche Panamera. I would love to know how Porsche manages to design their front engine AWD car to still maintain such good steering feel and precision.