Looking to put all seasons on my 991...have a jeep for bad weather but want something for the sub 40 degree weather and if I ever get caught out if we get a dusting or light snowfall. Am looking at Continental Extreme Contact DWS. They have exact size match to stock for my front 20" wheels but they don't have same size rears (295/30/20).....they do have 285/30/20 but on the Continental website they say this is only for up to a 10.5 inch rim. Then a few lines down they have a 275/35/20 that they say works with an 11" rim. So my question is ... How does a tire that is 10mm less wide work on a wider rim than a tire 10mm larger? I just don't get it but I want to order the right tires. Any clarity would be appreciated.