FWIW - I have the Bridgestone Dueler H/L Alenza on my 2004 X5 (not run flats) and I love them. Very quiet tire, low noise, great in the rain, I don't even put on my snow tires to go to the ski hill with them (probably should tho).

We replaced our conti runflats on the 2006 325i after 9,000 miles. They were horribly noisy. We bought the BMW mobility kit for the 2006 - it has a air compressor and some liquid to put in a tire in case of a flat. That solved the issue of not having a spare. We did buy a used 325i rim and got a tire for it and take that along on trips out of town. However the downside is there's not much room for luggage left.

The BMW dealer here gives us a case of ass each time we bring in the 2006 with non-runflats and wants us to buy new run flats for over $1,300. We paid about $800 for Yokohama's.

Anyway, on the X5 - you can get the same Bridgestone tire I have on my X5 (in 18 inchers at least) for the E70. $203 a piece from Tirerack.com.

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2007 328i Sport, Monaco Blue
2011 X35D - sold -Space Grey
2004 X5 4.4i - sold - Kalahari Beige
2001 X5 3.0i - sold - Pearl Beige
2006 325i Sport, Sonora Beige
2000 323i - sold - Sienna Red