Adjustment Work - Nussbaum WAB 02 CCT Instrucciones De Uso

4.4

Adjustment Work

Initial Remark: The software is set up in a way that normally
pressing ‚Continue'
This goes also for the adjustment screens. In the end, it does not
make too much sense to call the rear adjustment screen if there
is nothing adjustable at the rear axle.
In summary, the goal of the adjustment work is a satisfied
customer. This can be detailed with the following priorities:
- When driving straight, the steering wheel is level
- Car does not pull in one direction
- No abnormal wear & tear.
The prerequisites for successful adjustment are these:
- No more defective parts or parts with too much play in the
chassis anymore.
- Aligner is in optimum condition (levle of the lift, calibration).
If all these points are given, and you carefully avoid the traps
described in 4.2, the system will eliminate most of the problem:
You simply follow the adjustment screen, and adjust the values
into the center of the ‚ok' range, while the steering wheel is
perfectly straight and safely locked in that position.
There are two possible problems remaining:
- The steering wheel is not really level, or shifts during adjustment
work. This is being addressed by using the steering wheel level
(1 987 009 A74N, available as special accessory).
- First, you put the steering wheel in a position that looks straight
to you when sitting in the driver's seat. Ideally, you turn the
engine shortly on for that, and steer to the center with small
sweeps that are getting smaller all the time. Lock the steering
wheel by inserting the steering wheel holder. Only now, you
insert the steering wheel level. You have to adjust the bubble on
the steering wheel level (using the black thumb screw) in such
a way, that the bubble is centered between the two markings.
You do NOT change the position of the steering wheel during
that procedure. The steering wheel level is only your indepen-
dent ‚witness', whether the steering wheel position before /
after adjustment, and finally when doing a straight test drive, are
the same. Hint: The moment you get out of the driver's seat, the
bubble will no longer be centered, but that is fine. It only has to
be while you are back in the driver's seat.
AD G9001 N 29.10.08
will bring you to the next logical step.
- Symmetry of the play in the front axle not correctly identified.
This is about the freedom of movement that the wheels still have
in direction of toe, IN SPITE OF THE BLOCKED STEERING
WHEEL. With a brandnew car, this will not be too much more
than +/- 1', and thus is mostly neglectable. With much more
mileage or especially high wear and tear of bearings and other
parts, this play can be up to +/- 10'.
Example: Assuming a play of +/- 5', and positive total toe:
With correctly adjusted symmety, this can mean that driving
forward, the vehicle will have a front total toes of +12' , while
driving backwards, the toe will be as high as +32'. The difference
is explained with the fact that the front sides of the wheel are being
pressed apart while driving forward, i.e. the play is used to a fully
outward position of the wheel. This makes the toe value as small
as possible. Driving backwards, the wheels will use the play to go
to the fully inward position. With a toe average of +11' each ,i.e.
an average total toe of +24', this means minimum individual toe
of +6', and maximal individual toe values of +16'.
i The alignment robot system will always measure in the drive-
forward situation.
Now, what does this mean for toe adjustment:
Assuming the total toes of the car may be correct, but the steering
wheel is crooked to the left while driving straigt (Situation +7 / +7,
shown right). The measurement with straight steering wheel
could look like shown in the left two images:
It seems to be perfectly clear what has to be done: Both wheels
have to be adjusted about half of a degree to the right, so that they
will be +7/+7 with the steering wheel straight.
And this is where the challenge begins. While the right wheel
stays at the outer end of its play during the whole adjustment of
-24' to +7' (meaning a drive-forward situation), the left wheel will
only use the first 10' of adjustment to move within its play, from the
outside to the inside end of the play. And this equals a drive-
backward position. Although the numbers at the end of that
adjustment exercise look good (left), this will change for the left
wheel as soon as driving the car straight forward. Because in that
situation, the wheel will use its play to return from the inwar to the
outward position (right). Still refering to a level steering wheel.
But, where is the problem? Not in the total toe, that will be 10'
higher than intended. There should be no perceivably higher
wear&tear of the tyres due to that. Let's look instead, what the toe
values will do when driving straight. Remember that by definition
this means that both front toe values will be equal:
To make the toe values, the steering wheel will wander slightly to
the left. By a steering wheel angle that equals a toe change of 5'.
And such a steering wheel angle will be big enough to be
perceived as a crooked steering wheel by a critical customer.
Reason enough for the customer not to accept the result, reason
for starting over.
How can you avoid that?
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