Hi guys. Interesting thread. I have a 20d and my annual mileage is around 25.000, most of it by myself on business trips and on (European) freeways going 90-95mph.
I have P7s in summer and Dunlop 4 in winter and I must say after the first 30.000 miles I noticed the same problem on the front summer tires on the inside but absolutely nothing on the winter tires, although logic tells me their rubber should be softer.
I just cannot imagine it is the difference between 225s in winter and 245s in summer.