Just sharing what my problem ended up being...

Last week: Replaced the thrust arm/ball joint – vibration was still present.

Today: Just to make sure it wasn't something simple I had my tire shop check/balance all of the wheels (they were all ok, fronts were a tiny bit off but they fixed it). Anyway, while removing the front passenger side wheel when it was on the lift we found the sticking caliper – it was difficult to rotate and that wheel was much hotter than the others. So I'm glad I figured out what the cause was, it was driving me crazy. I'm going to try to rebuild the caliper first, if that doesn't work then I'll just find a used one I guess.

I also replaced (DIY) the wishbone control arms/ball joints today – the suspension feels much better and it helped lessen the vibration (from the brake).

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2003 X5 3.0i Sapphire Black/Black
Sport/Cold Weather/Premium Pkg.