I have been running 18" summer wheels on the F11 and 17" winters. The 18"s are none run flats and the winters are run flat. Both sets of tyres have more than the legal tread remaining but are coming towards the end of their legal lives. The roads here in East Cheshire are some of the worst in the country and have deteriorated over the last 10 years, so much so I have decided to put new all season tyres on the 17"s (none runflat Michellin Climate +) and sell the 18"s. I know the aesthetics of looking at the car will not be so good but ultimately it is more about comfort for me now I am over the age of 50 and it is an SE rather a M Sport so doesn't look too bad! Another reason for this is that we are in the process of getting planning consent for a new house within our garden which means the demolition of a large annex which currently stores the spare wheels. Won't have anywhere to store them in a couple of years and the E36 lives in the garage. Also I won't have to change them over every autumn/spring....those wheels and tyres are flamin heavy!!