If you have 17" rims with 225/50 tires, you can use SCC Super Z-6
sz137
http://www.scc-chain.com/tire-chain-...tirechains/661
For 18" rims with 225/45 tires, SCC Super Z-6
sz139
http://www.scc-chain.com/tire-chain-...tirechains/662
I have used the sz139 on my other vehicle (not on the X1 yet). They're low-profile, leaving a lot of clearance and did not hit any suspension parts. Also, they're relatively easy to install, compared to traditional chains.