What A Wheel Aligner Is; Characteristic Angles - Corghi EXACT LINEAR Manuel D'utilisation

WHAT A WHEEL ALIGNER
IS
An aligner or wheel aligner is defined as an
instrument for measuring characteristic align-
ment angles of a vehicle (see the "Characteristic
angles" section).
A wheel aligner consists of a central unit and four
measuring sensors for application to the wheels
of the vehicle.

CHARACTERISTIC ANGLES

1) ROC (Run Out Compensation). Off-centre
and plane error compensation.
ROC renders the angle measurements inde-
pendent of geometrical errors in the rim and/or
wheel mounting.
This procedure should be performed on all
wheels.
2) Toe.
Angle formed by the equatorial plane of the
wheel and the axis of symmetry or thrust axis of
the vehicle (Figs.7 and 8).
The axis of symmetry of the vehicle is the im-
aginary line which divides the vehicle in half
lengthways, while the thrust axis is the travel
direction established by the rear axle.
The units of measurement of toe are the degree
and the millimetre.
3) Camber or Inclination.
The angle formed by the equatorial plane of the
wheel and the vertical plane (Fig. 9): camber is
positive when the top of the wheel tilts outward.
The unit of measurement for camber values is
degrees.
4) Caster.
The angle formed between the vertical and the
projection of the steering axis onto the longitu-
dinal plane of the vehicle (Fig. 10).
Caster is measured with the wheels turned
through 10° or 20°.
The unit of measurement is the degree.
5) King pin angle.
The angle formed between the vertical and the
projection of the steering axis onto the transverse
plane of the vehicle (Fig. 11).
King pin angle is measured by locking the steer-
ing to 10° or 20°.
The unit of measurement is the degree.
6) Steering angle difference.
The difference between the values of the steer-
Operator's manual EXACT LINEAR
ing angles of the front wheels; by convention it
is measured when the wheel on the inside of the
bend is locked to 20° (Fig. 12).
The unit of measurement is the degree.
7) Misalignment of wheels on the same axle
or Set-Back.
The measurement of the difference in position
of one wheel in relation to the other, referred to
the perpendicular of the vehicle's longitudinal
axis (Fig. 13).
There are both front set-back and rear set-back;
the latter is not to be confused with the thrust
angle.
The unit of measurement is the degree.
8) Thrust angle.
The angle formed between the axis of symmetry
of the vehicle and the travel direction of the rear
axle (Fig. 14).
The unit of measurement is the degree.
9) Track difference.
Angle formed by the line joining the ground
contact points of the front and rear wheels on
the left-hand side and the line joining the ground
contact points of the front and rear wheels on the
right-hand side of the vehicle (Fig. 15).
The units of measurement of track difference are
the degree or the millimetre, only if the wheel
base is known.
10) Wheel base difference.
Angle formed by the line joining the ground
contact points of the front wheels and that of
the rear wheels (Fig. 16).
The units of measurement of wheel base differ-
ence are the degree or the millimetre, only if
the track is known.
11) Side offset.
Angle formed by the line joining the ground
contact points of the front and rear wheels on
the left-hand side, or the right-hand side, and
the vehicle's axis of symmetry (Fig. 17).
The units of measurement of side offset are
the degree or the millimetre, only if the wheel
base is known.
12) Axle offset.
Angle formed by the line bisecting the track differ-
ence angle and the vehicle's thrust axis (Fig. 18).
The units of measurement of axle offset are the
degree or the millimetre, only if the wheel base
is known.
EN
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