[Bob Bidonde]

Here is another look at the phase shift that nkaminar discusses in Post #12. When an out-of-balance wheel bounces, there is a bulge in the tire at the heavy spot that causes the wheel to bounce. When the bouncing of the wheel becomes severe, a resonance occurs that significantly increases the bouncing. The phase shift occurs at resonance, when the heavy spot and the bulge have a separation between them as the wheel goes into severe bouncing (resonance).