On-Vehicle Service; Measuring Wheel And Tire Runout - GMC G Service Manual

MEASURING WHEEL AND TIRE
RUNOUT
Runout measurements of the wheel and tire assembly
can be taken both on and off the vehicle. These measure­
ments can be taken radially and laterally. A dial indicator
equipped with a roller contact point, mounted on a heavy,
solid base is the measurement device. J 8001 and J 23672
are available for this procedure.
RADIAL RUNOUT
Radial runout is the egg-shaped difference from a per­
fect 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 gage, and the high
spot is the location of the maximum runout. On a rim, if
either flange is beyond specifications, replace the rim
(figure 3).
LATERAL RUNOUT
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 gage, and the high spot is the
location of the maximum runout. On a rim, if either flange is
beyond specifications, replace the rim (figure 4).
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.

ON-VEHICLE SERVICE

WHEELS AND TIRES 3E-5
1
A. Tire High Spot
B. Wheel High Spot
C. Wheel Low Spot
D. Tire Low Spot
Figure 4 — Measuring Lateral Runout
3. Raise the vehicle on a lift.
• 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 replace­
ment on the exact hub/rotor assembly.
5. Take either a radial or lateral runout measurement.
• Place the dial indicator in position.
• Rotate the tire and wheel assembly (or just the
wheel) to find its low spot. Adjust the dial indica­
tor to read zero.
• Rotate again to verify the low spot location —
the dial indicator must return to zero.
• Disregard any instantaneous dial jumps due to
welds, paint runs, scratches, etc. on the wheel.
• 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.
1. Dial Indicator
B-07451