Encountering Forcematching® or QuickMatching® Prediction Errors
Below are some reasons why the GSP9720JLR may not match or quantify the value
of the tire or the assembly.
x Incorrect Mechanical Wheel Mounting on the Shaft:
This can be caused from worn or damaged adaptors, rust, or debris on the
wheel, shaft, hub, adaptors, or a cone contacting a wheel on an irregular surface.
Verify proper mounting by performing a centering check.
x External Rim Measurement vs. Actual Bead Seat Measurement:
There is a high correlation between external and internal measurement, however
the operator must consider each wheel design individually. Some cast or closed-
faced wheels cannot be accurately measured externally. The tire must be
removed for accurate bead seat runout measurements.
x Incorrect Tire Bead Seating Procedures:
Tire technology is always changing. Today’s vehicles require the tire to be
designed to tightly adhere to the wheel, preventing slippage between the two
components. As a result, incorrect tire bead seating procedures are becoming
more of an issue in solving vibration complaints. In many cases, a wheel will
display high non-uniformity values because of increased tire bead interference,
wheel design, or improper bead seating procedures. If the tire is re-loosened
from the wheel and properly lubricated and remounted, the level of non-
uniformity may decrease dramatically. On sensitive vehicles, sometimes there is
benefit to slightly over-inflating the tire, deflating the air, and then re-inflating to
optimize bead seating.
x Insufficient Use of Tire Mounting Lube During Mounting:
“Lube is Good!” Proper lubrication on the tire bead and rim areas including bead
seat, hump, balcony, and drop center are vital in achieving proper seating of the
tire bead to the wheel assembly. Aggressive acceleration or braking should be
avoided for the first 500 miles to prevent tire to wheel slippage.
x Rim Safety Hump Design ‘Hangs Up’ Tire Bead During Bead Seating:
Some types of wheels use a square safety hump that may further inhibit uniform
tire bead seating. This further underscores the importance of proper lubrication
and bead seating procedures.
x Temporary Flat Spotting:
Flat spotting may occur when the tire is in one position for an extended period of
time, such as a parked vehicle, improper storage of the tire, and temperature
extremes. Measurements for force and balance will stabilize as soon as the tire is
driven for a few miles. This important issue can also affect traditional wheel
balancing procedures.
x Excessive Lateral Runout of Tire and/or Rim:
A tire or wheel with high lateral readings may affect the predicted results.
Do’s and Don’ts of Loaded Runout Measurement
x Tires may need to be warmed up to remove temporary flat spots prior to
testing.
x The tire/wheel assembly must be free of debris.
x Tire inflation pressure must meet vehicle manufacturers specifications.
x Verify the wheel is centered.
x Use the approved adaptors for GSP9720JLR. Use approved wing nut provided
and tighten with two hands to ensure full clamping force.
x Bare rim runout measurements are required if the wheel design does not permit
external measurement of the outer bead seat area.
x Use realistic Runout measurement values for the vehicle being tested.
x If chosen values have been exceeded, never use Runout measurement alone to
warranty a tire unless specified by the manufacturer.
GSP9720JLR Wheel Balancer Operation Instructions Road Force® Measurement Procedures
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