Not enough clearance for chains on the RS, or so they say. If you -1 size the wheels (to factory L wheels/tires) you can get away with chains. My Grand Cherokee couldn't use chains either. I wasn't really interested in buying a second set of all terrain tires just so I could use chains, so I bought a set knowing that I would never put them on. When the signs say "Chains required" even AWD/4wd vehicles need to have chains in the car. You don't have to put them on, but you're supposed to have them. In my Ru I just dropped the chains from my '91 Civic in the trunk for legality's sake.