Yes - its more the width of the tire...and the lack of a good grip tread on the 20's. Hence, a narrower tire is recommended. I'm opting for 255/50/19....I think...

from 214 with Bridgestone to 212 wearing Dunlop M3s! I had one day with the 214s in the snow and I sh.. my pants. The car was sliding down a 4-5 degree gradient.

Thats why they are called 'summer' tires ;)

Do the Latitude Tour HP's also come in RunFlats? Or will you have a compact spare (no 3rd Row seats)?

i am getting the 20's on my new car and need to choose a set for winter. i will go with 18" wheels and haven't decided on tire yet... but have used Michelin Pilot Alpin in past and they are pretty good. any thoughts?

and roughly... what should i be expecting to pay for all of this? i hope to get the wheels from BMW at cost (wonder what that is or how to verify?) and the tires at tire rack.

Are the problems mentioned above due to the size of the tires or the fact that they are summer tires. If one were to get 275/40-20's and 315/35-20's in an all season tire like the Michelin Latitude Tour HP would the problem be solved for the most part? Just reading the Michelin's specs and description they specifically mention that it has better handling in rain and snow. Here's the quote: "Secure-Lock™ Sipes help deliver better handling in rain and snow by locking together for greater rigidity."

I would assume a tire like this would eliminate most of the problems mentioned above......or...???

I live in the Los Angeles area where we obviously don't get snow, and maybe a couple of weeks of rain a year, so for the most part I would not be concerned. However, we do travel to the local ski areas maybe once or twice a year or so.....and usually the snow has been cleared off the roads, but on occasion we end up going before they have cleared the snow and have to drive up the mountain on snow. I think with our e53 we have driven in/on snow maybe 3 times in the 7 years that we have owned it.

So obviously given my situation I won't be getting "real" winter tires, but would you think that an all season tire like the Michelin Latitude Tour HP, or other similar tire from other manufacturers may be good enough for the occasional trip up the mountain with the possibility of having to drive on snow?

Now if I could only find an all season tire in those sizes that was also an RFT that would be nice, as we will be getting the 3rd row option and no room for a compact spare. The Bridgestone and Dunlop are the only two with the appropriate sizes that are also RFT, but they are summer tires.