I am going through the pain of finding the right tires for my 18" Sport Stars too. Last week I've fitted PU bushes + OEM rear bushes to my front wishbones. The car was driving like a dream again with the 235/45 17 Conti TS830P wintertires. I absolutely love those tires. However, as winter season has seem to come to an end I switched back to my Sporties yesterday, and got a reminder of an urgent need for new tires.
I have two cars running on these wheels, one on 4x 8J and one on 9J rears. I originally started the 8J set with Michelin Pilot Sport 2 tires, 245/40 93Y on front and 97Y XL on the back. At the first year I liked them, 2nd year came with the tramlining.
Meanwhile the 9J set (from Serek iirc) came from the UK to my driveway and after a refurb Good Year F2 Assy 2 tires were fitted. Didn't like them from day one. The good: fairly quiet, stable while breaking. But less grippy than the PS2's and I was having real issues with the 265's on the rear. Continuous vibrations even after 5x balancing done by multiple tire shops. In the end I had them trimmed and now it's gone by 80%. Overall I am not impressed with them.
As two PS2's from my 8J set were to replace last summer, I followed up the advise of a tire shop with experience with our kind of cars. They told me to look into Falken ZE 914 as that would be a more neutral tire which would fit with the characteristics of my heavy saloon. Or Dunlop RT's if I wanted a silent tire. I gave it a go and ordered 2 from Falken. After driving them for about 5.000km I must say the handling is indeed pretty neutral. The 914's don't shine at any point but they also don't really tramline. However, they also don't provide ANY rim protection. Which makes I want to replace them again with something else.
The good experience with my Conti 830's made me think to check out their summer line, but then I spent some time here reading the experiences you guys have and noticed the SC5 is surely not a good option. The SC3 MO does interest me. Also I was thinking of Michelin Primacy HP's, not in production anymore but still available in some shops. A few years ago I owned those in 235/45 17 and was very happy with them. At one point I was able to drive a set of 17" executive rims with the PS3's fitted (235/45) and they were almost equal to my PS2's regarding the negative aspects. Not an option.