While it is true a vibration is usually the result of a rotating source, it is not always the case. E.g., the rhythmic drumming caused by an open window in some circumstances is caused by air pressure oscillations from linear motion in a non-linear medium. Also, there are rotating sources for vibration other than the tires, and that is where determining the frequency is important. In particuar, there is some minute vibration in our steering wheel at engine rotation frequency, and others might get it at driveshaft speed.

Even if wheels are the source, balance might not be the issue. Uneven rotor wear can cause uneven frictional contact with the pads, causing an oscillation. Although I am not recommending routine driving with the steering damper removed, as a DIY check for the real source of the problem, this can aid diagnosis.

Steve

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'91 MB 190E 2.3
'08 RAV4 Ltd 3.5
'83 Lazy Daze m'home 5.7