Often the source of vibration is a bent axle or axle flange, or improper mounting of the wheel to the flange.
To check the run out of the flange, position a dial indicator against the outer flange surface of the axle. Apply slight
pressure to the center of the axle to remove the end play in the axle, and then zero the indicator. Slowly rotate the
axle one complete revolution and observe the readings on the indicator. The total amount of indicator movement is
the total amount of axle flange lateral run out. Compare the measured run out with specifications.