Ummm no. To all the previous replies. For 99% of the snow storms on the major highways to and from Lake Tahoe & Yosemite, having 4x4/All Wheel Drive, you will NOT need chains.

I've been up and down every year 4-5 times a year, in the worst storms. I have the 20" wheels, and have Toyo Proxies M&S. Of all the times up and down, the only time I EVER had any trouble, was with some ice on the way home. Was sooo slick, after coming to a stop, the X5 would just start sliding. So that is the ONLY time I've ever had the slightest of issues with big, fat, wide tires on the X5. And I've driven it in snow well past the bumper, say 18-24".

So, you should be just fine. Now, if you live in Lake Tahoe, or Yosemite, or Montana, Colorado whatever, then, yes, get some 18" wheels with some Bridgestone Blizzaks.

I'm personally going to pick up some 19's with Blizzaks just because I want to pull the big Ford's out of the snow :-).

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2007 X5 4.8i, sport, 20" OEMs, loaded
2008 M5 Indianapolis Red, Silverstone II interior