I had 18" RFTs on my E92 with Sport suspension Dave, and the ride is better now in my E46. They were rubbish, slippy in the cold and wet when I didn't particularly want them to be (entering roundabouts, went onto a motorway sideways a couple of times). The real kicker though was that they couldn't cope with Irish roads, with large lumps developing in the sidewalls a number of times due to potholes

That was 4 or 5 years ago so RFT tech maybe has moved on, but if I'd kept the car longer as a daily I would have switched to non-RFTs

I know that doesn't really answer your question, but judging from the 18"s I never felt any great desire to have a car with 19" RFTs