Certain models of tires tend to cause a buildup of static electricity when rolling. Sometimes this is audible from the radio when listening to an AM station with a weak signal. An extreme case would be when you get a little static shock after driving when your feet hit the pavement. Toll booth attendants sometimes get zapped this way also.
When I did the wheel bearings on the 300D, I found one of the springs with it's tab broken off, sitting in the grease. The possibility of loose parts getting ground up and mixed in the grease concerned me enough that I took the spring out of the other side also.
2004 C240 Wagon 203.261 Baby Benz
2008 ML320 CDI Highway Cruiser
2006 Toyota Prius, Saving the Planet @ 48 mpg
2000 F-150, Destroying the Planet @ 20 mpg
And remember folks, Only You Can Prevent Hilliary.