Staggered setups aren't really ideal. I suggest buying a wheel/tire set. Plus, the narrower/smaller, the better.

Thanks for all the info guys. I just moved to denver and this is my first experience w/ snow in the winter time.

I would stay away from this particular setup as your rear tires will have a larger overall diameter from the fronts. Hit up a discount tire, they have been very good to me in colorado and will beat any ebay or online price.

i've found them to be great. no problems driving cross-country last winter, or handling the northeastern ice and snow in the city and in the "mountains" heading to snowboarding in vermont and new hampshire.

they are rated highly at the tire rack, second only to another dunlop snow tire. the pirelli's are 5th in that survey...

The 235/55-18 will fit without any problem, but to match the front tire diameter you would need at the rear something like 255/50-18. You cannot put different diameter tires on a 4x4. Front and rear tires must have similar rotation, or you will mess up with the differencial pretty quickly. This is how a 235/55-18 (all around) will look on a 1,5" lowered X3:

http://photos1.hi5.com/0012/635/800/u3CHjo635800-02.jpg

I recommend Nokian Hakkapelitta.

New Hakkapelitta 5 SUV for my X5 this season. Can't advise on feedback just yet...

My OEM Scorpions work fine in Colorado Mountain country.

Cheers

I just got my wife some Goodyear Ultra Grip 235/55/17 from tirerack. They are excellent in the snow and great in the dry. I have had Dunlops, Pirellis and Michelin snow tires on different vehicles and these are right up there with the best of them in every aspect at a lower cost.

I finally received from BMW my new set of rims and tires for winter.

18" Dunlop Wintersport 3D

For the summer I have PZero Rosso (M Pack - Asymmetric 19"), but under +5 degres Celsius, Pirelli is like plastic :(