assume 2000 g of tread mass per tire (~20%)
assume 4 tires
6.1mg / 4 tires = 1.525 mg tire wear "emissions" per vehicle km per tire
assume total tire wear is 10x higher than "emissions": 15.25 mg total tire tread wear per vehicle km per tire
allows for ~131,000 km of tire life.
I am not so sure about the rational of classifying "re-suspension" as an "emission" however.