Same with mine, 20" Dunlops 17k miles the rears are perfect still 50% good. The left front is bald outside, right front is ok, both have less then 30% left in them. Had to put a new rubber set all 4, did an alignment before putting new ones on, dealer said it was bad. Car drove straight, with a slight hint to the left barely noticeable.
Retired: 2005 N52 E90 330i Sport 6AT
Retired: 2007 N54 E92 335i Sport 6AT
Current: 2012 M57 E70 X5 xDrive35D