CEMB USA C75 (A) - Manual (Page 24)

I 0202 - 24 GB
5.8 - ECCENTRICITY MEASUREMENT (OPTIONAL)
The much enlarged fi gures show the outer tyre surface and axis of wheel rotation.
Fig. A - shows measurement of the total Peak-to-Peak eccentricity defi ned as maximum radial deviation
of the tyre surface.
Fig. B - shows measurement of the eccentricity of the
1st harmonic, i.e. the eccentricity of that circle which
“recopies” the tyre shape, by averaging the local
deviations of the tyre from the round shape.
Obviously the P.P. measurement is normally greater
than that of the 1st harmonic. Tyre manufacturers
normally supply two different tolerances for the
two eccentricities.
At the end of the balancing spin it is possible to automatically measure the eccentricity of the
tyre through the SONAR sensor installed on the guard. The sensor should be positioned by hand
in front of the tyre tread.
GRAPH 1 : represents the actual Peak-to-Peak eccentricity.
GRAPH 2 : represents the eccentricity of the 1st harmonic. For a wheel in optimum conditions, such
graph should approach a straight line.
While rotating the wheel, the screen cursor indicates the current value, with the stage referred to the
eccentricity measurement sensor. Press pushbutton to access a panel where important information
about eccentricity is displayed, such as the imbalance effect which the fi rst eccentricity harmonic measured
may exert at an average speed of 120 km/h.
GRAPH 1 - (yellow)
GRAPH 2 - (red)
Fig. A Fig. B