Road Test

A tire vibration diagnostic procedure always begins with a road test. The road test and customer interview (if available) will provide much of the information needed to find the source of a vibration.

During the road test, drive the vehicle on a road that is smooth and free of undulations. If vibration is apparent, note and record the following:
^ the speed at which the vibration occurs.
^ what type of vibration occurs in each speed range-mechanical or audible.
^ how the vibration is affected by changes in engine torque, vehicle speed and engine speed.
^ type of vibration sensitivity-torque sensitive vehicle speed sensitive or engine speed sensitive.

Use the following explanation of terms to help isolate the source of the vibration:
If the road test indicates that there is tire whine, but no shake or vibration, the noise originates with the contact between the tire and the road surface.

Torque Sensitive

This means the condition can be improved or worsened by accelerating, decelerating, coasting or maintaining a steady vehicle speed and application of engine torque.

Vehicle Speed Sensitive

This means the vibration always occurs at the same vehicle speed and is not affected by engine torque, engine speed or transaxle range.

Engine Speed Sensitive

This means the vibration occurs at varying vehicle speeds when a different transaxle range is selected. It can sometimes be isolated by increasing or decreasing engine speed with the transaxle in NEUTRAL or by stall testing with the transaxle in gear. If the condition is engine-speed sensitive, the condition is not related to tires.