Road Test

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

During the road test, drive the vehicle on a smooth road. If vibration is apparent, note and record the following:

l The speed(s) at which the vibration occurs

l The type of vibration (mechanical and/or audible) occurring in each speed range

l How changes in vehicle speed, engine speed, and engine torque affect the vibration

l The type of vibration sensitivity (torque sensitive, engine speed sensitive, or vehicle speed sensitive)


Torque Sensitive

When the vibration is torque sensitive, the condition can be improved or worsened by accelerating, decelerating, coasting, maintaining a constant vehicle speed or applying engine torque.

Vehicle Speed Sensitive

When the vibration is linked to vehicle speed, the vibration always occurs at the same vehicle speed and is not affected by engine torque, engine speed, or transaxle gear selected.


Engine Speed Sensitive

When the vibration is linked to engine speed, the vibration occurs at varying vehicle speeds when a different transaxle gear is selected. It can sometimes be isolated by increasing or decreasing engine rpm with the transaxle in Neutral (N), or by stall testing with the transaxle in gear. If the vibration is linked to engine speed, the problem is probably not a wheel or tire condition.

If the road test indicates that the vibration is related to the tires or wheels, refer to the Symptom Chart in this section. If the vehicle leads to one side during the road test, refer to the Tire Lead Troubleshooting Chart in this section.

If the road test reveals tire whine, but no shaking or vibration, the noise is caused by contact between the tires and the road surface. Tire whine can be distinguished from axle whine because axle noise diminishes or changes according to load or speed. Tire noise remains the same over a range of speeds. A thumping noise usually means that the tire has flat or soft spots that make noise as they slap the road surface.


Symptom chart