Initial Inspection and Diagnostic Overview

Special Tools:

Special Tool(s)

Inspection and Verification
1. Inspect for signs of uneven tire wear that may indicate a damaged steering component, a need to balance or rotate the tires, or wheel alignment.
2. Check tires for:
- cuts.
- stone bruises.
- abrasions.
- blisters.
- embedded objects.
3. More frequent inspections are recommended when rapid or extreme temperature changes occur or where road surfaces are rough.
4. Tread wear indicators are moulded across the bottom of the tread grooves. Replace the tires when the tread wear indicators become visible across the tread.

Tire and Wheel Runout

NOTE: Perform runout checks only after the vehicle has been driven far enough to warm the tires and to avoid false readings caused by temporary flat spots on the tires.

To equalize tire wear, the tires should be rotated at recommended intervals.
Excessive radial and lateral runout of a wheel and tire assembly can cause roughness, vibration, wheel tramp, tire wear and steering wheel tremor.





The extent of the runout is measured with Dial Indicator. All measurements are made on the vehicle with the tires inflated to recommended inflation pressures.
Use Dial Indicator to measure the (1) radial and the (2) lateral wheel runout, and the (4) radial and the (3) lateral tire runout at the positions shown in the illustration. Mark the high point of radial runout of the tire on the sidewall, and mark the high point of radial runout of the wheel on the wheel face for future reference.

Match Mounting Tires
Match mounting is a technique used to reduce radial runout. Excessive runout is a source of vibration, shimmy and poor handling concerns. Use the following steps to reduce radial runout:
1. Dismount the tire and remount it with the mark on the tire 180 degrees away from the mark on the wheel.
2. Inflate the tire to specifications.
3. Measure the radial runout of the tire at the center of the tread face. If the radial runout is within specifications, the tire and wheel assembly can be used. If radial runout is not within specifications, replace the component(s) with the individual radial runout above specifications.

Tire Lead Diagnosis
Lead is the deviation of the vehicle from a straight path on a level road with no pressure on the steering wheel. Lead can be caused by:
- incorrect wheel alignment.
- dragging brakes.
- incorrect/uneven tire pressures.
- defective tires.

If defective tires are suspected in a lead condition, use the following steps to determine the defective tire:
1. Rotate the two front tires.
2. Road test the vehicle. If the vehicle leads to the opposite direction, one of the front tires is at fault.
3. Rotate the two front tires back to their original position.
4. Rotate one of the front tires with its corresponding rear tire on the same side of the vehicle.
5. Road test the vehicle. If the lead is corrected, install a new tire in the position that was rotated to the rear. If the lead remains, install a new tire on the opposite side of the vehicle.

Road Test-Vibration
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 ruts or crowning. If vibration occurs, 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 specifications, engine speed and engine torque
- 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.

Torque-Sensitive
The condition can be improved or worsened by accelerating, decelerating, coasting or maintaining a steady vehicle speed and applying engine torque.

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

Engine Speed-Sensitive
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 transaxle in N (neutral) or by stall testing with the transaxle in gear. If the condition is engine speed-sensitive, the condition is not related to the 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. Tire whine can be distinguished from wheel bearing noise because wheel bearing noise is diminished 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 making a noise as they slap the roadway.

CAUTION: Be sure to deflate tires to their proper pressures after this check is completed.

To verify that 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. The pitch or whine will change as the increased pressure changes the tire frequency.