DAF CF65, CF75, CF85 Series . Manual — part 1107

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1-1

General

REAR AXLE ALIGNMENT

ΧΦ65/75/85 series

9

6

1. GENERAL

1.1 DESCRIPTION OF POSSIBLE CAUSES OF REAR AXLE MISALIGNMENT

The drawing above shows several factors which

determine the position of the axle under the

vehicle:

1.

Difference in spring opening between the

spring assemblies on the left and right as a

result of the composition of the spring

assemblies, or of an unbalanced vehicle

load.

2.

Play between the centre bolt and the spring

assembly.

3.

Location of the holes in the chassis for the

attachment of the spring bracket.

4.

Dimensions of the spring bracket.

5.

Dimensions of the spring eye.

6.

Installation of spring assembly to the axle

housing.

?

2

1

3

4

5

6

C900386

REAR AXLE ALIGNMENT

1-2

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General

6

ΧΦ65/75/85 series

9

Points 2 to 6 are factors determined by the

manufacturer. Generally, the manufacturer will

ensure that the axle is (within a narrow margin)

positioned at an angle of 90

 in relation to the

central axis of the chassis.

Point 1, however, cannot always be controlled by

the manufacturer.

The difference in spring opening, which is

minimal for new spring assemblies, may increase

as a result of the "settling" of the spring assembly.

Furthermore, the superstructure and vehicle load

may be the cause of a difference in spring

opening and, consequently, misalignment of the

axle.

During spring movement the axle moves

backwards. If the springs on one side deflect

more than on the other side because of an

unbalanced vehicle or superstructure, this side of

the axle will move further backwards than the

other. As a result, the axle will no longer be at

right angles to the centreline of the vehicle.

The misalignment of the rear axle(s) may result in

increased tyre wear.

In case of a combination (truck and trailer or a

tractor and semi-trailer), a misaligned trailer or

semi-trailer may cause increased tyre wear on

the drawing vehicle.

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Inspection and adjustment

REAR AXLE ALIGNMENT

ΧΦ65/75/85 series

9

6

2. INSPECTION AND ADJUSTMENT

2.1 INSPECTION AND ADJUSTMENT, AXLE ALIGNMENT

General
-

Use only high-quality testing tools for

measurements. They must be calibrated

regularly and preferably be of the type that

can be calibrated before every use.

-

Position the vehicle on a flat and level

surface during the measurement.

-

Work with great accuracy.

-

Check the position of each wheel relative to

the centreline of the vehicle (twin wheels are

regarded as one wheel).

-

The misalignment of a rear axle is equal to

the average of the individual misalignments

of the left and right rear wheels.

-

For a vehicle combination (truck with trailer,

or tractor with semi-trailer), the alignment of

the vehicle combination as a whole must be

checked. A misaligned trailer or semi-trailer

may cause problems for the tractor.

Inspection of axle alignment
1.

Make sure that the load being carried is

representative of normal vehicle operation.

The load must be at least 40% of the

permissible loading weight and be evenly

distributed over the vehicle.

2.

Drive the vehicle straight to the test location

to avoid stresses in the chassis or in the axle

suspension system.

Note:

Avoid braking hard and do not put the vehicle

on the parking brake.

3.

Check the tyre pressure prior to the

measurement. Adjust if necessary.

4.

Check the spring opening of the spring

assembly and check the axle suspension for

play. Any defects should be repaired first.

5.

Consult the measuring tool instructions for

use and adhere to them.

6.

Calibrate the testing tool, if possible.

7.

Use the testing tool to measure the position

of each rear axle wheel in relation to the

vehicle centreline in mm/m.

REAR AXLE ALIGNMENT

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Inspection and adjustment

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ΧΦ65/75/85 series

9

8.

Determine the position of the rear axle

relative to the vehicle centreline, on the basis

of the positions of the two wheels.

9.

Check that the outcome is within the

permitted tolerance limits. If the

misalignment of the axle is beyond this limit,

the axle alignment needs to be adjusted.

10. If two or more rear axles are fitted, check the

position (non-parallelism) of the rear axles to

each other.

11. Check that the outcome is within the

permitted tolerance limits. If the

misalignment (non-parallelism) of the axle is

beyond this limit, the axle alignment needs to

be adjusted.

Determining the axle alignment
A practical aid to visualise the position of the axle

is the test report at the end of this section.

Mark the test readings as shown below.

Example 1
1.

Mark the test readings in the scales at the top

and side of the measured wheel.

In the opposite example (drawing 1) the

misalignment has been determined as a 3

mm/m toe-out in relation to the vehicle

centreline for the left wheel and a 3 mm/m

toe-in in relation to the vehicle centreline for

the right wheel.

2.

From the small circle at the bottom of the

wheel, draw a straight line to the test reading

indicated on the wheel top scale. This should

be done for both wheels (drawing 2).

The (mis)alignment of the wheels relative to

the vehicle centreline is now visible.

Drawing 1

-

+

+

-

-

+

+

-

3

3

3

3

W908002

Drawing 2

-

+

+

-

-

+

+

-

3

3

3

3

W908003