DAF CF65, CF75, CF85 Series . Manual — part 910

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200423

2-25

Inspection and adjustment

BRAKE SYSTEM AND COMPONENTS

ΧΦ65/75/85 series

6

5

2.17 INSPECTION, BRAKE DRUMS

For reasons of preservation, brake drums of new
vehicles must be cleaned with a cleaning agent.

The brake drums must be lifted using a hoist.
This is because there is a risk of limbs getting
trapped.

Always be careful when braking with new brake
drums and brake linings.

A brake drum which is thermally overloaded will
show heat cracks. These heat cracks will become
larger and deeper the longer the drum is used.
Thermal stress will thus increase the formation of
cracks.

Thermal stress may be caused by:
-

poor braking force distribution

-

seized brakes

-

jammed brake shafts or brake cylinders

-

insufficient clearance between brake lining
and brake drum with new brake linings

-

continuous application of the service brake
whilst driving.

Cracks that are permissible must be capable of
being removed when the drum is reconditioned.
See "Technical data".
If the cracks cannot be completely removed
during reconditioning of the brake drums,
accelerated brake lining wear can be expected.
If the brakes are once again thermally
overloaded, the edges of the cracks will rise
again, which will result in premature wear of the
lining, due to abrasion.

A brake drum may also show burns and local
hardened spots, also caused by high
temperatures.
Where the structure of the brake drum material
has changed, these burns must be removed by
reconditioning and grinding.
If the spots cannot be removed, braking will
always be accompanied by vibrations.
The brake linings will always first show rough
wear grooves at the respective spots.

A brake drum may be used until the internal
diameter has reached the maximum value.
See "Technical data".

As soon as this diameter is exceeded, the brake
drum must be replaced.

R 6 00 128

50

0.7

BRAKE SYSTEM AND COMPONENTS

2-26

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200423

Inspection and adjustment

5

ΧΦ65/75/85 series

6

Reconditioning of brake drums
If the lathe tool comes into contact with large or
deep hardened spots, listen for grating noises.

If a grating noise is heard, the brake drum must
be ground in order to obtain a perfectly round
wearing surface.

If the brake drum has been reconditioned, fit an
oversize brake lining, and turn it on the lathe.

2.18 INSPECTION, DRUM LININGS

In the case of separated brake linings, the words
"remnokzijde" and "draaipuntzijde" are marked
on the side of the lining. (This does not apply to
the 09N044 leading rear axle.) The brake lining
marked "remnokzijde" should be attached to the
brake cam. The brake lining marked
"draaipuntzijde" should be attached to the
pivoting point.

For the types of brake linings,
see "Technical data".

Always fit the same type of brake
linings to a vehicle.

-

When the brakes are applied, kinetic energy
is converted into heat.

-

Brake linings may be subjected to very high
temperatures.

-

A brake lining must work effectively in a very
wide temperature range. This means that the
coefficient of friction should as far as
possible be independent of temperature.

-

The brake lining must also have a long
service life.

-

The brake lining must be unaffected by
weather conditions, and should produce as
little noise as possible.

-

Excessive heat may cause changes to the
wearing surface of the brake drum.

}

©

200423

2-27

Inspection and adjustment

BRAKE SYSTEM AND COMPONENTS

ΧΦ65/75/85 series

6

5

Brake lining (including brake shoes)
inspection points:
-

braking performance after running in

-

glazing

-

moisture absorption (oil absorption)

-

lining wear

-

heat cracks

-

corrosion

-

swelling

Brake linings should be renewed when they have
been contaminated by oil or grease, or when the
lining is worn down to approx. 1 mm above the
rivet head, or to the wear indicator. The thickness
can be measured via the inspection holes in the
back plates.

Corrosion
Brake shoes may exhibit considerable corrosion,
as a result of excessive ageing and the action of
moisture on the assembly face.

Incorrect bearing surface
The surface is no longer smooth. The lining no
longer has a sufficient mounting surface at the
edges of the rivet recess and ruptures during
riveting. The lining could be released from the
shoe and lifted. As a result, the clearance
between lining and drum decreases or
disappears completely.
Even when the brakes are not applied,
the temperature of the brake increases and,
as a result, heat cracks may occur in the bearing
surface of the brake drum.

Bearing pattern
When turning the brake lining, the lining will bear
on the radius of the drum with the entire brake
surface. Such a bearing pattern guarantees the
best possible breaking performance from the
beginning. The turning of the brake lining may be
carried out on a brake lining lathe, or with a
special dummy back plate on a special lathe.
The bearing pattern of the brake lining can be
improved by turning the brake lining to a diameter
which is max. 1.0 mm smaller than the drum
diameter. So, in the case of a brake drum
diameter of 420 mm the brake lining should be
turned to a max. diameter of 419 mm.

M6002

R600129

BRAKE SYSTEM AND COMPONENTS

2-28

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200423

Inspection and adjustment

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ΧΦ65/75/85 series

6

Wheel brake with modified lining diameter
(see drawing)
The lining will bear on the centre of the lining
length first, after which the bearing pattern is
extended from the centre towards the ends.
This will prevent an (unduly) heavy self-servo
action during the running-in period.

The brake lining must be turned gradually; i.e. not
too much lining material should be removed in
one operation.
If this instruction is not followed, the lathe tool will
bend and be inclined to lift the leading brake shoe
of the brake cam. The initial bearing pattern will
then not be at its best.
It is not necessary to turn "clean" the entire
surface. It is sufficient to touch 75% of the surface
with the lathe tool.

A wheel brake lining with insufficient bearing
surface
The ends of the brake lining are still free. As a
result, the load on the smaller brake lining surface
will be considerably heavier at the same press-on
force. As a result, the lining will be squeezed;
the temperature will increase and there will be
accelerated lining wear, until the braking surface
is eventually correct.
In the case of reconditioned brake drums, it is
recommended that a new lining should be turned
to the radius of the brake drum after it has been
fitted.

R600130

R600131