When getting 2nd tire set with their own TMPS sensors, make sure you get those (takeoffs) from cars built prior to Oct 2010, as BMW had changed sensors around that time (thus signal receiver on your car will not be able to pick up signal from sensors installed on X5 built after 10/10).

Or you can get sensors separately and create your own combo of rims/sensors/rubber. Just make sure to mention that you have pre-2011 E70 model when purchasing sensors!

Don't even try the Dueler's in the snow. I did this past Feb, right after I picked up the vehicle, and they are downright dangerous in the cold and snow. I bought a set of 19's with Hankook IPikes.
Also, a thinner width tire will yield very little MPG improvement. The 4.8 is a hog on gas. It is what it is.

Or get a tire pressure gauge?

Haha. Ard, should I disengage the rain-sensing wipers too?
But seriously folk, are 18" better in snow than 19" with the same tires?

It is not about measuring the actual pressure (yes, make sure you do have a good gauge)... It is about not having computer throwing error codes that it can't detect presure in the wheels!

I used to have both 19" (on my 2008 X5) as well as 18" (on my current 2011, winter setup)... I say 18" is better as they are "softer" overall for winter driving conditions - better handle potholes.

Status update: I purchased a set of 212 (19") rims off of eBay.
-Does anyone know if I can simply take off the 214's (20") and pop the 212's on?
-Can I use these 212 without TPMS sensors and turn off the error warning?
-If I go with non-RFT's on the 19" and get a spare, will the spare also work with the 20"s?
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-I need to decide if I want to go with dedicated winter tires for the 19's or go All-Season and possibly sell the 20's or go with All-Seasons non-RFTs on the 20's too and sell the 19's. Hence my questions about the spare working for both sets of tires.

I took a roadtrip to PA and am even more in lust with the X5. I got my MPG avg. up to 19mpg! Yeahhhh!!! Who needs a Prius???

The 18s would be better in snow if more narrow. they dig deeper for more grip.

As far as MPG, a harder narrower tire (all season, etc) would get slightly better MPG but not a big difference.

FYI, you need a larger diameter tire to improve MPG, not smaller. The larger tire reduces RPMs for a given speed.

hello folks, i have an 06 4.8 with the staggered 20" diamaris tires. im looking for just winter tires from nov-march. what do you folks suggest? am i better with an all season 18" rim and tire or just go with a winter 20" tire??

The question really shouldn't be about tire diameter, it's tire width. The thinner the tire, the better in the snow - all other things being equal.

That said, I've run 20" Pirelli Scorpion Ice/Snow on my X5M for three winters - they worked great.

I'll be doing the same thing with my new X5.