Initial Inspection and Diagnostic Overview

INSPECTION AND VERIFICATION
^ To maximize tire performance, inspect tires for signs of improper inflation and uneven wear which may indicate a need for balancing, rotation or front suspension alignment.
^ Tires should also be checked frequently for cuts, stone bruises, abrasions, blisters and for objects that may have become imbedded in the tread. More frequent inspections are recommended when rapid or extreme temperature changes occur or where road surfaces are rough or occasionally littered with debris.
^ As a further visible check of tire condition, tread wear indicators are moulded into the bottom of the tread grooves. The tire should be replaced when these indicator bands become visible.

WHEEL AND TIRE CHECKING PROCEDURE
Tire Wear Diagnosis
Inspect tires for wear. Abnormal or excessive wear may be caused by incorrect wheel alignment, wheel/tire imbalance or improper tire pressure.

Road Test
A tire vibration diagnostic procedure always begins with a road test. The 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 vehicle speed, engine speed, and engine torque
^ Type of vibration sensitivity: torque sensitive, vehicle speed sensitive, or engine speed sensitive

Sensitivity Descriptions
The following explanations help isolate the source of the vibration.
Torque Sensitive
This means 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 the vibration always occurs at the same vehicle speed and is not affected by engine torque, engine rpm, or the transmission gear selected.
Engine Speed Sensitive
This means the vibration occurs at varying vehicle speeds when a different transmission 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 the tires.

Tire Noise/Whine
If the road test indicates 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 the tire is flat or has soft spots making a noise as they slap the roadway.
Tire whine can be distinguished from axle noise. Axle noise diminishes or changes according to load or speed. Tire whine remains the same over a range of speeds.
To verify the tire noise is not associated with shake or vibration, inflate the tires one at a time to 345 kPa (50 psi) and check for a change in the sound.

CAUTION: Be sure to deflate tires to their proper pressures after this check is completed. Overinflated tires will adversely affect vehicle handling.