My 2007 Z4 3.0si has broken rear springs. Seems sensible to replace the struts while replacing the springs... does anyone know if it's worth finding a kit from, say, Bilstein or another aftermarket group, or am I not going to notice the difference between that and OEM? I don't do track, but drive with some enthusiasm as conditions allow. I will say, when i got the car, used, a few years ago the runflats rode like they were made of rock. I lived with it for a while with some sense of disappointment (I've had many BMWs but this is my only Z4, and I was expecting better). Anyway, I finally wore out the tires and replaced them with new P-Zero runflats, and the difference is like night and day. Any major complaints I'd had, had really been associated with old, worn-out rubber, not with run-flats in general. Any residual complaint is probably related to the broken springs, so want to do right by my ride! Thanks for any advice or experience you've had.
If you've been happy with the performance and ride quality of stock/oem with your other bimmers, I'd say stick with that. I'd think most aftermarket sport shocks are going to have you unhappy with a stiff suspension ride-quality for the vast majority of your driving. Sport shocks/spring kits, yes, substantial difference - performance, but, at the expense of everyday comfort & usability; inevitable trade-off
