I have a 2012 X5d w/ staggered 20" wheels. 315 on back, 275 on front. I'm looking at replacing my run-flats for conventional, either Michelin or Conti DWS 06. It appears that Michelins run about 25% pricier than the Contis (on TireRack). Any preferences to either of these tires??

As well, I will go to a space-saver spare (I have no 3rd row seating). Are these space-savers (wheel & tire) available aftermarket??. As well I'd like to have it securely mounted in the trunk cutout. Does any after market company make these?? Is there a secondary market, i.e. "used" for these spares???

Thanks