Initial Inspection and Diagnostic Overview
Special Tool(s)
Inspection and Verification
1. Inspect for signs of uneven tire wear which may indicate a damaged steering component, a need to balance and/or rotate 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 or occasionally littered with debris.
4. Tread wear indicators are molded across the bottom of the tread grooves. Replace the tires when the tread wear indicators become visible.
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.
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 Radial Runout Gauge. All measurements are made on the vehicle with the tires inflated to recommended inflation pressures.
Measure the (1) radial and the (2) lateral wheel runout at the positions shown in the illustration.
Use Radial Runout Gauge to measure the (4) radial runout of the tire at the center and outside ribs of the tread face and the (3) lateral runout on the tire sidewall as shown in the illustration. Mark the high points of radial runout 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. Mark the wheel at the same point as the mark previously made when measuring the tire runout.
2. Dismount the tire and remount it 180° on the wheel so the original mark on the tire is opposite the mark on the wheel.
3. Inflate the tire to specification.
4. Measure the radial runout with Radial Runout Gauge at the center of the tread face. If the radial runout is reduced to acceptable guidelines, the tire can be used. If the radial runout remains excessive, check the wheel runout.
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 pressure.
- 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, replace the tire that was rotated to the rear. If the lead remains, replace the front tire on the opposite side of the vehicle.
Road Test-Vibration
NOTE: For complete road test procedure.
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 speed, 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, 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 NEUTRAL or by stall testing with the transaxle in gear. If the condition is engine speed sensitive, the condition is 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 has flat or soft spots making a noise as they slap the roadway. 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.
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.