Mine does it, and both ball joints are relatively new. I replaced the rotors a year or so ago, and the problem went away for a few months, and then came back.
95 Contour Zetec, ATX (wrecked, sitting in the barn)
95 Mystique Zetec, MTX
2000 Taurus SEL 3.0L Duratec
1994 Crown Victoria LX 4.6 V8
1993 Chevy Silverado 4.3 V6
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