On my rear dimaris 315s, the thick line down the middle of the tire seems really worn, but the outside (both left and right) have lots of tread. On the front the thick line looks normal, so is it time for new tires or are they fine? (BTW '06 w/ 14500 miles)

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2006 BMW X5 4.8is Lemans Blue/Beige/Dark Maple
-Nav, Comfort Seats, Heated Steering Wheel,
Rear Airbags, AUX Input
2009 BMW M3 Space Grey/Black/Carbon
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