2A
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.
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Tire runout.
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Wheel runout.
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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]:
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Caused by tire out of round
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1.
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Smooth road
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[B]:
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Caused by tire stiffness variation
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2.
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Suspension movement (loaded runout)
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[C]:
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Caused by rim bent or out of round
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