when a tyre is already worn, it will continue to wear on that area regardless of what side you have put it on or whether your wheels have been aligned.

You need fresh new tyres on whatever axle is wearing and a 4 wheel alignment, and wheels should not be aligned while you have unevenly worn tyres on the car.

I had same issues. Make sure you go to someone who knows what they are doing with a digital alignment machine.

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E53 x5 3.0D Sport. Black.