Interestingly RFTs are not mentioned once in this article but "High performance tires" and "wider tires or a "Plus Size" tire and wheel package" seem to help you do some tramlining.

All change to donuts.

ABC

I have an 07' 550i on which I put 19 inch wheels and non-run flat tires. As far as ride quality there is an obvious difference. The runflats are much harsher and stiffer riding, particularly over small imperfections in the road (small potholes and crumbling pavement) and small sharp bumps (expansion joints and the lip on driveway ramps etc..). Obviously there is a safety benefit to runflats that cannot be ignored. My priority is on handling. And the softer rubber of a non-funflat tire along with the flex in the sidewall allows for a significantly greater amount of grip while actually providing a better ride. This combination for me was compelling (and turned out to be 100% true BTW). One HUGE factor for me that I only discovered after riding on the non run flats was that they are much better in wet conditions. Apparently the stiff sidewall and harder rubber of the run flats makes them more like hockeypucks in the rain. Think of this: why would BMW change its very stubborn mind about runflats on the LCI 550i sport? Simple: They offer the highest performance and so they should go on the highest performing non-M 5 series (you'll notice there was never a thought of the current M5 ever having runflats). The 535i I'm sure will be a sensational car, but it is not, and never will be, BMW's flagship 5, and so the runflats remain OEM. {I don't mean to flame the 535 at all. I'm sure dynamically it has some advantages over the 550, but the more expensive car with more cylinders and displacement holds the title of flagship, period - i.e. Audi's A8 W12 is dynamically inferior to the S8, but the 12 is the flagship}.

http://www.tirerack.com/tires/tiretech/tec...e.jsp?techid=47

ABC

I have been very neutral about the entire RFT debate until I had the opportunity to drive RFT in the moring and Non RFT in the afternoon - granted that there are significant chasis differences between a 17" wheel clad 3 series SE and 19" clad 5 series M Sport however the subtlety of feeling the road through the chasis and suspension of the m sport 5 versus the head-but i got from an RFT SE was no illusion!

I am convinced that RFT's are a perfect compromise between safety, ride and performance in a country where they invest in roads - not in a country like the UK where the majority of roads are knitted together with badly filled in water / gas / electrical main trenches........

Sorry for chopping and underlining your writing 550isport, but that's it.

Mine is on comfort and handling!

Since you are also from the "North" and do know what these winters does to the roads,
I have nothing more to add,
except 18"'s the max.


PS. The LCI 550i still comes with 17" wheels as standard from Dingolfing :whistle:

PS2. The M models do not use RF tyres.

True. I never really had harsh criticism for my 18" RFT setup - going to 19" non RFT has brought about little difference in ride comfort (at least on Dutch roads) but a NOTICEABLE improvement in handling. Rear 275 and spacers probably account significantly to this. I'm happy with both the ride comfort and handling with my new setup !

HA, drive in Los Angeles with RFs and you will yearn for your roads.

You choose your wheel size and you take the ride.

ABC

Huh?

What I read on this thread is that even with the extra inch and therefore lower profile/aspect ratio of the 19", the ride will be much better than what I have now.

Run Flats are great in my opinion. Its a hassle getting nails fixed... because the tire company takes roughly 20 minutes plus taking it off, but yeah... its great. The ride of the 18's are a bit rougher than the regular rims i have had, but traction with the 18 550i sports rims have given me better grip and handling. Awesome bridgestone tires. For me, I got used to the ride. But then again i dont have the sport suspension, so it might compensate for it.