I'd probably chalk it up to bad tires, some of the high performance types have very soft rubber and wear out really fast. Believe it or not 15-20K is not unheard of. I had the same Michelins on our wagon and they lasted 40K+ so I felt good about them on the E300 this time instead of the pirellis. I also run them slightly over inflated now (35 PSI in back and 32 up front when measured cold) Underinflation can wear them very fast.

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Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz