Hi Guys, new to the forum. My 2011 X1 M Sport came with 18 inch Pirelli's but 225/45 for front and 255/40 for rear (from memory, but definitely different profile). They grip fine for summer tyres in summer conditions but aree noisy. Mine is a UK 2.0 130 kw disel engine and the engine noise could not drown out the road noise on motorways (your US freeways).
Now I am hunting high and low for run-on-flats winter tyres with 68db or less noise on 225/50 17 inch to experiment. Found only one in UK websites Dumlop Winter SP3 run on flats but dealers seem only to stock this one non-run-flat. Boo. Any UK forum members have ideas ?