Initial Inspection and Diagnostic Overview
Inspection and Verification1. Inspect for signs of uneven wear that may indicate a need for balancing, rotation, front suspension alignment, damaged tie-rod, or steering idler arm.
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 foreign material.
4. Tread wear indicators are molded into the bottom of the tread grooves. Install a new tire when the indicator bands become visible.
Tire and Wheel Runout
Excessive radial and lateral runout of a wheel and tire assembly can cause roughness, vibration, wheel tramp, tire wear, and steering wheel tremor.
When carrying out any inspection or repair procedures on wheels and tires, follow the preceding safety precautions.
Before checking runout, and to avoid false readings caused by temporary flat spots in the tires, check runout only after the vehicle has been driven far enough to warm the tires.
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 and with the front wheel bearings adjusted to specifications.
Tire Runout
Use Radial Runout Gauge to measure radial runout of the tire at the center and outside ribs of the tread face. Mark the high points of radial runout for future reference. Radial runout should not exceed specifications.
Wheel Runout
Measure radial and lateral wheel runout at the positions shown in the illustration. Runout should not exceed specifications.
Wheel Centering O-Ring Seal
The front hub and rear axle wheel pilots are fitted with rubber O-rings which help center the wheels. Remove the O-ring, clean the machined groove, and clean and lubricate the O-ring if required. Install a new O-ring if damaged. O-rings should be pulled on (not pushed) so that the yellow paint identification stripe is visible after installation.
Road Test
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 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
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 transmission in NEUTRAL, or by stall testing with the transmission 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 the tire has flat or soft spots making a noise as they slap the roadway. Tire whine can be distinguished from axle noise because axle 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 correct pressures after the following 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.