I put a set of BMW OE P/N Dunlop Wintersport 3D Runflats with BMW OE wheels. Same as what's listed on BMW Canada's website on my 555xi sport. The tires came mounted, with center caps, and TPMS.
For a 550, I would not trust the OE Goodyear LS's for winter (in my climate). Just in the days that temps dropped in the 30's, and in the wet I could tell the car did not have tons of grip. I ordered a set of wheels and tires from the dealer--the nice part is that since it's an OE P/N that's an assembly, it's covered under my tire and wheel package. BMW parts was extremely competitive on price.
So far the temps have dropped into the low 30's at night with some wet roads and some minor ice. I'm glad I got these tires.
The ride is good, and the tires are quiet. They are downsized to 18" but I've seen no deterioration in ride. Turn in is sharper.
I put them on 100 miles ago and examined the wheels and tires. No dents, no bubbles. I think Gen II of the LS' might be improved. I did run my psi at 37 front/38 rear. I'm running 36 all around.
12 550xi Dark Graphite Metallic II. Convenience, Cold, Driver's Assistance, Premium Sound, Sport, BMW Apps