Tire Vibration Diagnosis

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

Type of vibration sensitivity:
- torque sensitive
- vehicle speed sensitive,
- or engine speed sensitive.

The following explanations will help isolate the source of vibration:

Torque Sensitive
This means that the condition can be improved or made worse by accelerating, decelerating, coasting, maintaining a steady vehicle speed, or applying engine torque.

Vehicle Speed Sensitive
This means that the vibration always occurs at the same vehicle speed and is not affected by engine torque, engine speed or gear selection.

Engine Speed Sensitive
This means that the vibration occurs at varying vehicle speeds when a different gear is selected. It can sometimes be isolated by increasing or decreasing engine speed with the transmission in neutral or by stall testing with the transmission in gear. If the condition is engine speed sensitive, the cause is probably not related to tires.

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.

A thumping noise usually means that the tire is flat or has soft spots making a noise as they slap the roadway. Tire whine can be distinguished from axle noise, as tire whine remains the same over a range of speeds.