IMPACT 4.04.
00 24/04/2025
Chassis ID Path
BB 338966 5109/Diagnostics//Brake adaption
Model Identity
FM (4) 121429513
Publish date ID/Operation
13/05/2009 50021-3
50021-3 Brake adaption
Note: As the illustrations are reused for several different variants, some details may therefore differ from the variant you
are working on. The essential information in the illustrations is, however, always correct.
Special tools: 9998052, 9992976, 9996461, 9996460, 88800263
Contents
Check and adjustment of load-sensing valve (RSS-AIR)
Check and adjustment of load-sensing valve (RSS-LEAF)
Check and adjustment of load-sensing valve (Trailer)
Check and adjustment of control valve (towing vehicle)
Check and adjustment of the control valve (trailer)
Check of brake adaption
Conclude the brake adaption
General
Brake adaption should be done with a fully loaded vehicle so that the valves go to their full load position. Use the actual
weight when printing. To get a load increase for an unloaded vehicle, the axle can be pulled down against the rollers of
the brake tester to simulate load-sensing valves in the full load position. The use of the roller brake tester and its
equipment is not covered here, please refer to the manufacturer's manual.
Brake adaption must be done after the vehicle brakes have been evaluated and any faults remedied and that the
Copyright to this documentation belongs to the Volvo Group. No reproduction, copying, change, amendment or other similar disposal is entitled without prior written consent by
the Volvo Group
The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.
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IMPACT 4.04.00 24/04/2025
brakes have been run in.
Note: Design and function Brake adaptation
Warning
Do not change the brake arrangement for the truck or trailer, the construction is correct from the manufacturer
and is registration inspected. Changing the brake arrangement and/or tyre size will alter the brake curve and a
new registration inspection is required.
Caution
Follow the instructions carefully to avoid personal injury or damage to products or equipment.
Check and adjustment of load-sensing valve (RSS-AIR)
Note: The vehicle must be unloaded when checking and adjusting the load-sensing valve.
Caution
Tighten the test nipple by hand to prevent damage to the test outlet.
Connect the test nipple to outlet (4) unregulated pressure from the foot brake valve.
Copyright to this documentation belongs to the Volvo Group. No reproduction, copying, change, amendment or other similar disposal is entitled without prior written consent by
the Volvo Group
The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.
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IMPACT 4.04.00 24/04/2025
Connect the test nipple to outlet (43). For simulating bellows pressure.
Connect the test nipple to the brake cylinder on the drive axle's service brake part (Px pressure).
Copyright to this documentation belongs to the Volvo Group. No reproduction, copying, change, amendment or other similar disposal is entitled without prior written consent by
the Volvo Group
The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.
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IMPACT 4.04.00 24/04/2025
If the vehicle is equipped with pilot valve (FBREG-LS) test nipple must also be connected to the brake cylinder on the
front axle's service brake part (Px pressure).
Connect hoses (9996461) between (R) on a calibrated pressure gauge (9998052) and the parking tank or the
workshop air supply, load-sensing valve, front brake cylinder (equipped with pilot valve) and the rear brake cylinder test
nipples (9992976).
Special tools: 9998052 9992976 9996461
Copyright to this documentation belongs to the Volvo Group. No reproduction, copying, change, amendment or other similar disposal is entitled without prior written consent by
the Volvo Group
The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.
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Place out chocks and release the parking brake.
Fit the exhaust hose and start the engine or alternatively charge the compressed air system with external compressed
air.
Copyright to this documentation belongs to the Volvo Group. No reproduction, copying, change, amendment or other similar disposal is entitled without prior written consent by
the Volvo Group
The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.
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Set, using reduction valve (R), a simulated bellows pressure of 1 bar on manometer (A). Apply the foot brake (pump
the brakes a little so that the valves regulate in the correct position) until the pressure on manometer ( B) shows 7 bar.
Read off the outgoing pressure to the rear brake cylinder from manometer (C).F If the vehicle is equipped with pilot
valve (FBREG-LS), the pressure to the front brake cylinder is read off from the manometer ( D). Make a note of the
value. Release the foot brake. Repeat the check with a simulated bellows pressure using reduction valve ( R) to 3 bar
and 5 bar on manometer (A). When the bellows pressure is 5 bar, the outgoing pressure should show 7 bar on
manometers (C) and (D). Make a note of the values. If the values do not coincide, adjust the load-sensing valve.
Copyright to this documentation belongs to the Volvo Group. No reproduction, copying, change, amendment or other similar disposal is entitled without prior written consent by
the Volvo Group
The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.
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The diagram sign can differ between different vehicles.
Check that the pressure on manometer (C) coincides with the diagram. Note the bellows pressure value at 1 bar, 3 bar
and 5 bar for a possible adjustment of the load-sensing valve.
10
Note: Before adjusting the load-sensing valve and when a new check is to be done, the foot brake must be released so
that manometer (B) reads 0 bar. Adjustment is done with adjuster screw (1). To increase the pressure, turn outwards
and to reduce the pressure press to the brake cylinders, turn inwards.
Get the values noted earlier and adjust the outgoing pressure to the brake cylinders so that it lays within the approved
area (if the values do not correspond, carry out a new check according to the previous steps).
11
After the adjustment is completed with a simulated bellows pressure ( A) of 1 bar a check and adjustment must be done
in the same way with a bellows pressure of 3 bar and 5 bar. After a completed adjustment of the load-sensing valve, a
final check must be done.
12
Copyright to this documentation belongs to the Volvo Group. No reproduction, copying, change, amendment or other similar disposal is entitled without prior written consent by
the Volvo Group
The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.
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IMPACT 4.04.00 24/04/2025
If the vehicle is equipped with a pilot valve, check the pressure on manometer (D). Note the value with bellows
pressures of 1 bar, 3 bar and 5 bar. After the load-sensing valve has been adjusted, compare with pressure (C). If the
outgoing pressure from the pilot valve (FBREG-LS) does not correspond with the diagram sign, the pilot valve must be
replaced.
13
Copyright to this documentation belongs to the Volvo Group. No reproduction, copying, change, amendment or other similar disposal is entitled without prior written consent by
the Volvo Group
The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.
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Screw out knob (Rand check that manometer (A) shows 0 bar. Disconnect the hose from the test nipple outlet (43) for
simulated bellows pressure measuring, Apply the foot brake until manometer (B) shows 7 bar. Read off manometers (C
and D) that the existing bellows pressure reduces the brake pressure to the brake cylinders. Release the foot brake
and check that the manometers (B, C and D) show 0 bar.
14
After the check and adjustment is completed, disconnect the hoses, test nipples and compressed air instrument.
Check and adjustment of load-sensing valve (RSS-LEAF)
15
Weigh and note the vehicle's actual drive axle pressure and bogie pressure.
Note: The time for weighing is not included in the method.
16
Copyright to this documentation belongs to the Volvo Group. No reproduction, copying, change, amendment or other similar disposal is entitled without prior written consent by
the Volvo Group
The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.
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Load sensing valve with built-in relay valve.
Caution
Tighten the test nipple by hand to prevent damage to the test outlet.
Connect test nipple to the test outlet for ingoing unregulated pressure from the foot brake valve.
17
Load sensing valve without built-in relay valve.
Copyright to this documentation belongs to the Volvo Group. No reproduction, copying, change, amendment or other similar disposal is entitled without prior written consent by
the Volvo Group
The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.
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Connect test nipple to the test outlet for ingoing unregulated pressure from the foot brake valve.
18
Connect test nipple to the brake cylinder's Px pressure for service brakes at the drive axle.
19
If the vehicle is equipped with pilot valve (FBREG-LS) the test nipple is connected to the brake cylinder's Px pressure
at the front axle.
20
Copyright to this documentation belongs to the Volvo Group. No reproduction, copying, change, amendment or other similar disposal is entitled without prior written consent by
the Volvo Group
The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.
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Connect hoses (9996461) between (B) on a calibrated pressure gauge (9998052) and load-sensing valve with relay
function (M) and without relay function (U) and (C) on the pressure gauge to the rear brake cylinder's test nipple
(9992976). If the vehicle has a pilot valve, connect hose (9996461) to (D) on the pressure gauge to the front brake
cylinder's test nipple (9992976).
Special tools: 9998052 9992976 9996461
21
Copyright to this documentation belongs to the Volvo Group. No reproduction, copying, change, amendment or other similar disposal is entitled without prior written consent by
the Volvo Group
The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.
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Fit the exhaust hose and start the engine or alternatively charge the compressed air system with external compressed
air.
22
Apply the foot brake using a pedal strut until the ingoing pressure is 7 bar. Unregulated pressure (B) to the
load-sensing valve.
23
The diagram sign can differ between different vehicles.
Read off the outgoing Px-pressure (C) and compare with the diagram.
24
Copyright to this documentation belongs to the Volvo Group. No reproduction, copying, change, amendment or other similar disposal is entitled without prior written consent by
the Volvo Group
The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.
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The diagram sign can differ between different vehicles.
Check the length of the lever at the valve. If necessary, adjust the lever to the correct position ( f) and length to get the
correct pressure according to the diagram.
25
Copyright to this documentation belongs to the Volvo Group. No reproduction, copying, change, amendment or other similar disposal is entitled without prior written consent by
the Volvo Group
The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.
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Load sensing valve without built-in relay valve.
Move the lever to the lug that shows full load position. In this position, full brake pressure of 7 bar must be obtained.
26
If the vehicle is equipped with pilot valve (FBREG-LS) the pressure on manometer (D) must be checked. Read off how
high the pressure should be and compare it with the pressure on manometer (C). If the outgoing pressure from the pilot
valve (FBREG-LS) does not correspond with the diagram sign, the pilot valve must be replaced.
27
Note: Load sensing valve with built-in relay function. The lever automatically goes to full load position 7 bar when the
wired is loosened.
Simulate a wire break by loosening the return spring and let the lever go to the return position. Apply the foot brake
using a pedal strut until the ingoing pressure is 7 bar, the outgoing pressure becomes the same as the ingoing
pressure. Also applies to pilot valve.
28
Copyright to this documentation belongs to the Volvo Group. No reproduction, copying, change, amendment or other similar disposal is entitled without prior written consent by
the Volvo Group
The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.
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Connect the return spring. Remove test nipples, hoses, pedal strut and instrument.
Check and adjustment of load-sensing valve (Trailer)
29
Copyright to this documentation belongs to the Volvo Group. No reproduction, copying, change, amendment or other similar disposal is entitled without prior written consent by
the Volvo Group
The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.
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Example of sign and its location.
Check and adjust the load-sensing valve/valves according to the trailer's sign. If there is no sign, contact the trailer
manufacturer for the specifications and for how the valve is adjusted.
30
Copyright to this documentation belongs to the Volvo Group. No reproduction, copying, change, amendment or other similar disposal is entitled without prior written consent by
the Volvo Group
The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.
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Example of connecting a calibrated pressure gauge (9998052) to the front and rear brake cylinders and the
load-sensing valve.
Load sensing valve with air suspension.
Special tools: 9998052 9992976 9996461
31
Copyright to this documentation belongs to the Volvo Group. No reproduction, copying, change, amendment or other similar disposal is entitled without prior written consent by
the Volvo Group
The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.
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Example of connecting a calibrated pressure gauge (9998052 ) to the front and rear brake cylinders and load-sensing
valve with relay function (M) or without relay function (U).
Load sensing valve with leaf spring suspension.
Special tools: 9998052 9992976 9996461
Check and adjustment of control valve (towing vehicle)
32
Start the PC/roller brake tester Fill out the job card.
33
Copyright to this documentation belongs to the Volvo Group. No reproduction, copying, change, amendment or other similar disposal is entitled without prior written consent by
the Volvo Group
The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.
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Connect pressure gauges to the brake circuits for the front axle (Px) and rear axle (Px) and the trailer's compressed air
connection control line (Pm). Use test nipple (C) for connection to tool 88800263 (B) or 9996460 (A).
Special tools: 9996460 9992976 88800263
34
Carry out brake test on the brake tester for each axle. Refer to the manufacturer's manual for details of how the test is
done.
35
Copyright to this documentation belongs to the Volvo Group. No reproduction, copying, change, amendment or other similar disposal is entitled without prior written consent by
the Volvo Group
The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.
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Example of diagram printout.
Note: There are different legal requirements for the retardation values. The brake test is pre-programmed for the
domestic market's legal requirements. The retardation values can be chosen, however, if a computer is connected. The
slope of the curve is decided by the mechanics of the brakes and cannot be affected when adjusting the control valve.
Print the retardation diagram for the total value of the towing vehicle. Check and adjust the towing vehicle's retardation
curve correctly in the corridor by adjusting the towing vehicles control valve (trailer brake valve).
36
Copyright to this documentation belongs to the Volvo Group. No reproduction, copying, change, amendment or other similar disposal is entitled without prior written consent by
the Volvo Group
The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.
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Remove the silencer from the control valve (trailer brake valve).
37
Adjust the control valve's control pressure using the adjuster screw. (Philips head). Counter-clockwise increases the
pressure and moves the starting pressure to the right. Clockwise reduces the pressure and moves the starting
pressure to the left.
Caution
Copyright to this documentation belongs to the Volvo Group. No reproduction, copying, change, amendment or other similar disposal is entitled without prior written consent by
the Volvo Group
The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.
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The screw is plastic and if it becomes damaged, the valve must be replaced.
The adjustment range is 5 turns, 1 turn changes the (Pm) pressure approx.: 0.2–0.4 bar. Earlier control valves had a
slotted metal screw and the opposite adjustment direction..
38
Carry out a brake test according to earlier steps. Make sure the retardation curve lays in the centre of the corridor. The
start pressure (Px) must be between 0.5 and 0.8 bar.
Check and adjustment of the control valve (trailer)
39
Copyright to this documentation belongs to the Volvo Group. No reproduction, copying, change, amendment or other similar disposal is entitled without prior written consent by
the Volvo Group
The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.
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IMPACT 4.04.00 24/04/2025
Connect the pressure sensor to the front brake circuit (Px) and rear (Px) and the trailer compressed air control line (Pm
), use test nipple 9992976 (C) and tool 88800263 (B) alternatively 9996460 (A).
Special tools: 9996460 9992976 88800263
40
Perform the brake test. Read the brake tester manual. Use the retardation diagram in the tester for the total value for
the trailer.
41
Copyright to this documentation belongs to the Volvo Group. No reproduction, copying, change, amendment or other similar disposal is entitled without prior written consent by
the Volvo Group
The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.
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Example of a diagram printout.
The curve shows a too high Pm pressure which must be reduced to move the curve to the centre of the corridor by
adjusting the towing vehicle's control valve (brake valve).
Note: The are different legal requirements for the retardation value. The brake test is pre-programmed for the domestic
market's legal requirements. The retardation values can be chosen, however, if a computer is connected. The slope of
the curve is decided by the mechanics of the brakes and cannot be affected when adjusting the control valve.
Print the diagram. Check and adjust the trailer retardation curve correctly in the corridor by adjusting the trailer control
valve (brake valve).
42
Copyright to this documentation belongs to the Volvo Group. No reproduction, copying, change, amendment or other similar disposal is entitled without prior written consent by
the Volvo Group
The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.
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Example of an adjustable control valve (brake valve).
If there are no details of how the control valve is adjusted, contact the manufacturer.
Note: Certain control valves are not adjustable. Check with the manufacturer regarding changing to adjustable valves.
43
Carry out a brake test according to earlier steps. Make sure the retardation curve lays in the centre of the corridor. The
Copyright to this documentation belongs to the Volvo Group. No reproduction, copying, change, amendment or other similar disposal is entitled without prior written consent by
the Volvo Group
The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.
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start pressure (Px) must be between 0.5 and 0.8 bar.
Check of brake adaption
44
Example of a diagram printout that shows a well adapted vehicle.
A. Towing vehicle
B. Trailer
C= Difference in retardation
Print a retardation curve for the towing vehicle and the trailer and check that the curves follow each other and lay in the
centre of the corridor and that the difference in retardation does not exceed 0.1–0.2 m/s². The difference in retardation
can be permitted to increase at higher pressures. The important factor is that the start pressure of the curves is the
same.
Conclude the brake adaption
Copyright to this documentation belongs to the Volvo Group. No reproduction, copying, change, amendment or other similar disposal is entitled without prior written consent by
the Volvo Group
The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.
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45
Disconnect the pressure sensor from the brake system.
46
Switch off the PC/brake tester.
Copyright to this documentation belongs to the Volvo Group. No reproduction, copying, change, amendment or other similar disposal is entitled without prior written consent by
the Volvo Group
The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.
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