I'm not so sure rear ball joints are absolutely needed, especially for a 2005 model, unless it is high mileage.

My X5 is an '03 with 115k miles. I would say that 75% of that was driving in the city, such as New York city and now Saint Louis. The roads are rough on the suspension. However, when I took it to my last alignment, the tech was able to get the camber back to spec at -1.7 deg. So my suggestion is to pay for that $90 alignment first before you start throwing money at it.

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