OK on yours. Ours 2015 M3 Grand Touring 225/45/18 very stock. Not as smooth on our potholes and repair mounds at 70 mph as our old 929 with full tire pressure (or handle as well). BUT remember real drivers LIKE road feel. Low profile tires are more sensitive to suspension design. Good road feel may save you life some day.I agree with everything you said. I could have written it myself. Almost. Except the part about low profile tires riding better. If undamped travel in high profile tire causes ride deterioration, then shouldn't lower inflation pressures in a given tire size also ride worse? That increases undamped travel as well. Isn't this why tires are pneumatic and not solid in the first place? If undamped travel causes a worse ride, wouldn't solid tires with no give provide the best ride.? Don't think so. Are low-profile tires ruining your ride?
, In my Particular case I did not notice any deterioration in handling with slightly lower rear tire pressures. Had I a skid pad handy or even some nice tight curvy roads to push hard on around here to make comparisons , I might have been able to to discern a difference.
Also, using less air at the lightly loaded rear is an old autocrosser's trick to reduce understeer in front heavy cars, though in that case pressure is added at both ends, just a lot more at the front.
That's why I did not reduce air at the front much.
Yes. it will increase wear at the back but likely still nowhere near the wear rate of the heavily loaded front end. Tires need rotated less often?
Fuel economy will be worse. I need to make real world comparisons there, to see if I can live with the difference. I could except 1mpg less but probably not 2.
I should have done a better job of evaluating the car before purchase. Based on reviews and my short test rides on relatively smooth roads, I expected it to ride and handle in a similar manner to my 2016 Golf or 2014 3. I was smitten by its good looks and quiet, attractive cabin.
It rides a little worse than the old 3. A lot worse than the Golf. It handles slower than either.
By the way, stock tire is a 215/45/18, not a 225.