Component Tests and General Diagnostics
NOTE:^ Some vehicles are sensitive to tire and wheel assembly runout. Tires that are satisfactory on one vehicle might be unsatisfactory on another. When analyzing vibration problems, it is important to keep this in mind. In addition, different wheel positions on a vehicle may have different sensitivity levels. Check for wheel runout or total wheel and tire runout in the following cases:
a. If the tire and wheel vibration occurs below 40 miles per hour.
b. If all wheels are balanced within one ounce of static balance and five ounces of dynamic balance, and a vibration occurs.
c. If there appears to be a bulge in a tire or an out-of-round condition as a tire rotates on a balancer.
d. If any wheel damage is noticed.
e. If there is a poor wheel fit on the hub and the vehicle exhibits vibration.
^ Wheel runout should be measured with an accurate dial indicator. Measurements may be taken with the wheel installed on or off the vehicle using an accurate mounting surface such as on a wheel balancer. Measurements may also be taken with or without the tire mounted on the wheel.
^ Radial runout and lateral runout should be measured on both the inboard and outboard rim flanges. With the dial indicator firmly in position, slowly rotate the wheel one revolution and record the total indicator reading. If any measurement exceeds specifications, and there is vibration that wheel balancing will not correct, the wheel should be replaced. Disregard any indicator readings due to welds, paint runs, scratches, etc.
^ Radial runout is the egg-shaped difference from a perfect circle. Measure tire radial runout from the center tire tread rib although other tread ribs can be measured as well. The total runout is the reading from the gauge, and the high spot is the location of the maximum runout. On a rim, if either flange is beyond specifications of 1.015 mm (0.040 inch) for steel wheels, replace the rim.
^ Lateral runout is a sideways variation causing a twist or wobble and is measured on a side surface. On the tire and wheel assembly, measure the sidewall of the tire as close to the tread shoulder design edge as-possible. The total runout is the reading from the gauge, and the high spot is the location of the maximum runout. On a rim, if either flange is beyond the guidelines of 1.143 mm (0.045 inch) for steel wheels, replace the rim.
MEASUREMENT PROCEDURES
1. Inflate the tires to specifications.
2. Warm up the tires prior to taking measurements to eliminate flat spotting (newly installed tires usually do not require warming up).
3. Raise the vehicle on a lift and, if measurements will be taken off the vehicle, mount each tire and wheel assembly on a dynamic balance machine.
4. Mark the tire and wheel assemblies for exact replacement.
^ Mark a wheel hub bolt and its exact position on the wheel.
^ Mark each tire and wheel assembly for replacement on the exact hub/rotor assembly.
5. Take either a radial or lateral runout measurement.
a. Place the dial indicator in position.
b. Rotate the tire and wheel assembly (or just the wheel) to find its low spot. Adjust the dial indicator to read zero.
c. Rotate again to verify the low spot location-the dial indicator must-return to zero.
d. Disregard any instantaneous dial jumps due to welds, paint runs, scratches, etc. on the wheel.
e. Rotate the tire and wheel assembly (or just the wheel) and note the amount of variance (runout) from zero. Locate and mark the high spot.
6. If there is a large difference in runout measurements from on vehicle to off vehicle, the runout problem is likely due to excessive runout of the bolt circle or hub.
7. If measured runouts are not within the guidelines, proceed to "Vectoring" to correct the problem.