Description of Highway Speed Vibration Diagnosis
Wheel unbalance causes most of the highway speed vibration problems. If a vibration remains after dynamic balancing, its possible causes are as follows.
Tire runout.
Wheel runout.
Tire stiffness variation.
Measuring tire and/or wheel free runout will uncover only part of the problem. All three causes, known as loaded radial runout, must be checked by using a Tire Problem Detector (TPD). If TPD is not available, alternative method of substituting known-good tire and wheel assemblies on the problem vehicle can be used, although it takes a longer time.
[A]: Caused by tire out of round 1. Smooth road
[B]: Caused by tire stiffness variation 2. Suspension movement (loaded runout)
[C]: Caused by rim bent or out of round