Replaced Run-Flats
Just took off (and stored to put back on at lease end) the RTFs and put on Continental ExtremeContact DWS06 A/S, which are the only tires which would fit (and still had to go up one size front and back). RTFs are in storage for the next two years of lease, when they will go back on for lease return (only have 6k miles on them).
After about a week of driving:
1. More compliant sidewall makes potholes, manhole (is that the wrong term nowadays?) covers, etc., much less jarring; still know I went over it because of the 19" wheels, just not up through the spine giving me a headache. Real bad holes/bumps tend to make you feel like you're being moved a couple of inches at most to one side or the other, but not enough movement to make you feel like you're losing any traction or control. RTF hops have moved me in the past several FEET, even into the other lane on the highway at 60+mph...scary!
2. Very comfortable and quiet highway ride, even with top down, unless road is old with aggregate showing...but that's really to be expected with this car and wheels.
3. Less precise than Max Summer RTFs for turn in on harder cornering and wander a touch when cornering; again to be expected with all the sipping on All Seasons. Actually not as bad as I had expected; feel confident driving on twisty Oregon coastal highway.
4. Good in the rain, even hard rain. Felt a touch light in hard rain with water on roadway, but still turned precisely.
Overall, I'm REALLY pleased with the change over, esp., since I know from experience with RTFs that they just get harder and harder after 5-10k miles and thus more and more uncomfortable and less reliable for harder driving because of their unpredictability over bumps, etc.
One other note: On such a small, light, low to the ground car like the Z4is, 19" wheels are overkill to me. They aren't going to give the car a huge traction boost on the road (at the track that might be a different story) and whatever benefit one gets from the potentially wider tire, is offset by the fact that they have to be very low profile tires and thus are going to be unnecessarily harsh during normal driving due to the extremely small sidewall (I don't know if the very high air pressure in the tire helps the ride or makes it more harsh). I'd say that good 18" wheels would be better for a daily driver like mine is. IMHO
