ISO 7635:2003

INTERNATIONAL ISO
STANDARD 7635
Second edition
2003-11-15
Road vehicles — Air or air-over hydraulic
braking systems for motor vehicles
(including those with electronic control
functions) — Test procedures
Véhicules routiers — Dispositifs de freinage à air comprimé ou
hydropneumatiques pour automobiles (y compris ceux à fonctions de
commande électronique) — Mode opératoire d'essai

Reference number
©
ISO 2003
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©  ISO 2003
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ii © ISO 2003 — All rights reserved

Contents Page
Foreword. v
1 Scope. 1
2 Normative references. 1
3 Terms and definitions. 1
3.3 Antilock braking system (ABS) . 2
3.4 Vehicle loading. 2
3.5 Air system pressures. 3
4 Symbols. 4
5 Test site conditions . 5
5.1 Test site. 5
5.2 Road surface conditions . 6
5.3 Ambient conditions. 6
6 General requirements. 7
7 Recommended test sequence . 8
7.1 Preparation and static checks and tests . 8
7.2 Basic performance tests — Unladen . 8
7.3 Failure tests — Unladen . 9
7.4 ABS tests — Unladen . 9
7.5 ABS tests — Laden . 10
7.6 Failure tests — Laden. 10
7.7 Basic performance tests — Laden . 11
8 Vehicle preparation. 11
8.1 Documents and basic date. 11
8.2 Braking system condition and bedding. 11
8.3 Adjustment of braking equipment. 12
8.4 Tyre conditions. 12
8.5 Apparatus and instrumentation. 12
9 Static tests and checks . 13
9.1 Control force vs. line pressure . 13
9.2 Capacity of energy sources . 13
9.3 Service braking system — Response time measurement. 14
9.4 Automatic braking. 15
9.5 Antilock warning lamp and mode change check. 15
9.6 Tests on vehicles equipped with spring brake actuators. 16
10 Basic performance tests — Unladen . 17
10.1 Type 0 test (service braking system cold brake effectiveness, engine disconnected). 17
10.2 Type 0 test (service braking system cold brake, engine connected) . 17
10.3 Parking braking system — Hill holding test. 18
10.4 Secondary braking system test. 18
11 Failure tests — Unladen . 18
11.1 Service braking system partial failure test (type 0 test, cold brake effectiveness, engine
disconnected). 18
11.2 Failed-load-sensing device test. 19
12 ABS tests — Unladen . 19
12.1 ABS failure. 19
12.2 Determination of peak coefficient of adhesion on high-adhesion surface. 19
12.3 Determination of adhesion utilization on high-adhesion surface .20
12.4 Determination of adhesion utilization on low-adhesion surface.22
12.5 Additional checks.22
13 ABS tests — Laden .24
13.1 General.24
13.2 Additional split adhesion test .24
13.3 Energy consumption on low-adhesion surface .24
14 Failure tests — Laden .26
14.1 Service braking system partial failure test (Type 0 test, cold brake effectiveness, engine
disconnected) .26
14.2 Failed load-sensing device test .26
14.3 Energy source failure test .27
15 Basic performance tests — Laden .27
15.1 Parking braking system — Hill-holding test.27
15.2 Parking braking system — Dynamic test.28
15.3 Type 0 test (service braking system cold brake effectiveness, engine disconnected) .28
15.4 Type 0 test (service braking system cold brake, engine connected) .28
15.5 Warning device test (low stored energy) .28
15.6 Energy storage capacity test .28
15.7 Type II or Type IIA tests (downhill, endurance braking test) .29
15.8 Type I test (fade test) .31
Annex A (normative) Typical braking equipment.33
Bibliography.35

iv © ISO 2003 — All rights reserved

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 7635 was prepared by Technical Committee ISO/TC 22, Road vehicles, Subcommittee SC 2, Braking
systems and equipment.
This second edition cancels and replaces the first edition (ISO 7635:1991), which has been technically revised.

INTERNATIONAL STANDARD ISO 7635:2003(E)

Road vehicles — Air or air-over hydraulic braking systems for
motor vehicles (including those with electronic control
functions) — Test procedures
1 Scope
This International Standard specifies procedures for testing the air or air-over hydraulic braking systems, with
and without antilock braking system (ABS), of vehicles of categories M and N (excluding M and N ) as
1 1
defined in UNECE R.E.3. The values given in square brackets and the values in the tables are taken from
ECE Regulation No. 13 for information.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO 611, Road vehicles — Braking of automotive vehicles and their trailers — Vocabulary
ISO 1176:1990, Road vehicles — Masses — Vocabulary and codes
ISO 3833, Road vehicles — Types — Terms and definitions
ISO 6786, Road vehicles — Air braking systems — Identification of connections on units
ISO 7634:2003, Road vehicles — Compressed-air braking systems — Test procedures
ECE Regulation N° 10, Uniform Provisions Concerning the Approval of Vehicles of Categories M, N and O
with Regard to Electromagnetic Stability
ECE Regulation N° 13:1996, Uniform Provisions Concerning the Approval of Vehicles of Categories M, N and
O with regard to braking, incorporating the 09 series of amendments without supplements
1)
UNECE R.E.3:1997, Consolidated Resolution on the Construction of Vehicles
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 611, ISO 1176 and ISO 3833 and
the following apply.
3.1
air-over hydraulic braking system
braking system having stored pneumatic energy, hydraulically actuated brakes and transmission means
incorporating a pneumatic-to-hydraulic converter

1) United Nations Economic Commission for Europe
See Figure A.1.
[ISO 611:2003, definition 4.2.2]
3.2
pneumatic braking system
full-air braking system
braking system in which the control and energy are transmitted from the point of application to the brakes by
pneumatic transmission devices
[ISO 611:2003, definition 4.2.3]
See Figure A.2.
3.3 Antilock braking system (ABS)
3.3.1 Categories of ABS
3.3.1.1
Category 1
ABS which meets all the requirements of ECE Regulation No. 13:1996, Annex 13
3.3.1.2
Category 2
ABS which meets the requirements of ECE Regulation No. 13:1996, Annex 13, excepting paragraph 5.3.5 (no
braking rate on split-adhesion surfaces is prescribed)
3.3.1.3
Category 3
ABS which meets the requirements of ECE Regulation No. 13:1996, Annex 13, excepting paragraphs 5.3.4
and 5.3.5 (all split-adhesion tests are omitted)
3.3.2 Wheel control
3.3.2.1
directly controlled wheel
wheel whose braking force is modulated according to data provided at least by its own sensor
3.3.2.2
indirectly controlled wheel
wheel whose braking force is modulated according to data provided by sensor(s) of other wheel(s)
NOTE ABS with select-high control are deemed to include both directly and indirectly controlled wheels. In systems
with select-low control, all sensed wheels are deemed to be directly controlled wheels.
3.4 Vehicle loading
3.4.1
laden vehicle
vehicle laden so as to reach its maximum design total mass (Code: ISO-M07)
NOTE See ISO 1176:1990, 4.7.
3.4.1.1
laden motor vehicle other than semi-trailer tractor
motor vehicle laden to the maximum design total mass (Code: ISO-M07) specified by the vehicle
manufacturer and acknowledged by the technical services
2 © ISO 2003 — All rights reserved

NOTE 1 See ISO 1176:1990, 4.7.
NOTE 2 This mass may exceed the maximum authorized total mass (Code: ISO-M08) permitted by national
regulations. See ISO 1176:1990, 4.8.
NOTE 3 Mass distribution on the axles is to be stated by the vehicle manufacturer. In the event of several load
distribution patterns being planned, the distribution of the maximum design total mass among the axles is such that the
load on each axle is proportional to the maximum load for each axle defined by the manufacturer.
3.4.1.2
laden semi-trailer tractor
semi-trailor tractor laden to the maximum design total mass (Code: ISO-M07) that is technically feasible, as
specified by the vehicle manufacturer and acknowledged by the technical services, except that the load
defined by the manufacturer may be repositioned halfway between the kingpin position and the centre-line of
the rear axle(s), so as to compensate for the dynamic load transfer from the semi-trailer
NOTE See ISO 1176:1990, 4.7.
3.4.2
unladen vehicle
vehicle at its complete vehicle kerb mass (Code: ISO-M06) plus the mass of the required instrumentation
NOTE See ISO 1176:1990, 4.6.
3.4.2.1
unladen motor vehicle other than semi-trailer tractor
motor vehicle laden to complete vehicle kerb mass (Code: ISO-M06)
NOTE 1 See ISO 1176:1990, 4.6.
NOTE 2 During the tests, the fuel quantity in the fuel tank is to be maintained at least to 50 % of its capacity.
NOTE 3 An increase up to 200 kg mass over this mass is allowed. This corresponds, for instance, to the driver, one
observer and instrumentation. If necessary, the appropriate vehicle mass may be removed.
NOTE 4 For a vehicle without body, the manufacturer is to declare the minimum axle loads for a bodied vehicle.
3.4.2.2
unladen semi-trailer tractor
vehicle laden to complete vehicle kerb mass (Code: ISO-M06) and including the fifth wheel or a load
equivalent in value and position
NOTE See ISO 1176:1990, 4.6.
3.5 Air system pressures
3.5.1
pressure indicated by the manufacturer (of the vehicle)
reservoir pressure specified by the manufacturer from which it is possible to achieve the required efficiency for
service braking
NOTE It is the basis for the energy storage capacity test (see 15.6).
3.5.2
maximum pressure
pressure available for normal operation, i.e.
 the cut-out pressure, in the case of an installation with a pressure regulating device
 [90] % of the asymptotic pressure, in the case of an installation with a pressure-limited compressor
3.5.3
minimum pressure
pressure available for normal operation, i.e.
 the cut-in pressure, in the case of an installation with a pressure regulating device
 [90] % of the pressure indicated by the manufacturer, in the case of an installation with a pressure-limited
compressor
4 Symbols
Table 1 — Symbols used in this International Standard
Symbol Description Unit
a Mean deceleration m/s
m
d Mean fully developed deceleration m/s
m
E Wheelbase m
The adhesion utilized by the vehicle: quotient of the maximum braking rate with the ABS
ε
operative (z ) and the coefficient of adhesion (k)
AL
ε The ε value measured on axle i (in case of a power-driven vehicle with a Category 3 ABS)
i
ε The ε value on the high-adhesion surface
H
ε The ε value on the low-adhesion surface
L
F Actuating force daN
F Normal reaction of road surface under dynamic conditions with the ABS operative N
dyn
F F on axle i N
idyn dyn
F Normal reaction of road surface on axle i under static conditions N
i
F Total normal static reaction of road surface on all wheels of power-driven (towing) vehicles N
M
Total normal static reaction of road surface on the unbraked and non-driven axles of the
a
F N
Mnd
power-driven vehicle
Total normal static reaction of road surface on the unbraked and driven axles of the power-
a
F N
Md
driven vehicle
F 0,01 F + 0,015 F (rolling resistance) N
Wm Mnd Md
2 2
g Acceleration due to gravity (9,81 m/s) m/s
Height of centre of gravity specified by the manufacturer and agreed by the Technical
h m
Service conducting the approval test
h Height of fifth wheel coupling (kingpin) m
k
k Coefficient of adhesion between tyre and road
k k-factor of one front axle
f
k k-value determined on the high adhesion surface
H
k k-value determined on axle i for a vehicle with a Category 3 ABS
i
k k-value determined on the low adhesion surface
L
k value of adhesion for 100 % slip
lock
k k-factor of the power driven vehicle
M
k Maximum value of the curve “adhesion versus slip”
peak
4 © ISO 2003 — All rights reserved

Table 1 (continued)
Symbol Meaning Unit
k
k-factor of one rear axle
r
p Maximum pressure supplied by the towing vehicle in the supply circuit for the trailer kPa (bar)
max
p 65 % of p kPa (bar)
1 2
p Pressure level specified by the manufacturer enabling the prescribed performance of the kPa (bar)
service braking system to be achieved
P Mass of motor vehicle kg
M
P Maximum permissible mass of the trailer allowed to be towed by the power-driven vehicle t
T
R Ratio of k to k
peak lock
s Stopping distance m
t, t , ∆t Time interval s
i
t , t , t Pump-up times (ref. 9.2.1) min
1 2 3
t Mean value of t s
m
t Minimum value of t s
min
v Vehicle speed km/h
v Maximum speed of the vehicle km/h
max
v Lower speed limit for the antilock energy consumption test km/h
u
V Reservoir volume l
z Braking rate
z Braking rate of the vehicle with the ABS operative
AL
z Mean braking rate
m
z Maximum value of z
max
z Mean braking rate of front axle
mf
z Mean braking rate of rear axle
mr
z z of the power-driven vehicle on a “split-surface”
MALS AL
a
F and F : in case of two-axle power-driven vehicles these symbols may be simplified to corresponding F symbol.
Mnd Md i
5 Test site conditions
5.1 Test site
The test site shall be of sufficient size, without obstacles, to provide a safe testing environment.
The test site shall have a road of sufficient length prior to the test area to enable the test speeds to be attained.
The test area should be
a) of sufficient length to allow for poor braking performance, and
b) of sufficient width to allow for poor directional stability under braking.
5.2 Road surface conditions
5.2.1 Surface
5.2.1.1 The test area shall be a dry, smooth, hard surface, free of loose material and providing a peak
coefficient of adhesion of about [0,8].
5.2.1.2 Additionally, for the testing of vehicles equipped with ABS, a surface providing a peak coefficient
of adhesion k of [0,3] or less is required. It shall be preceded and followed by a surface in accordance with
peak
5.2.1.1 of sufficient length on the approach side to enable the test speeds to be attained.
Until such test surfaces become generally available, tyres at the limit of wear, and higher values of k up to
peak
[0,4] may be used. The actual value obtained and the type of tyres and surface shall be recorded.
For testing of vehicles fitted with ABS of Category 1 or 2, it is also necessary for a low-adhesion surface (k ) to
L
have a high-adhesion surface (k ) on at least one side so that the split-adhesion tests can be performed. Both
H
surfaces shall be sufficiently wide to allow, using the vehicle under test, the peak coefficients of adhesion to
be determined separately.
The above-described surfaces shall be such that k is W [0,5] and k /k is W [2]. If any doubt arises as to
H H L
whether this requirement has been met, it is necessary to ascertain the peak coefficients of adhesion using
the procedure detailed in 12.2 and 12.4. It is always necessary to measure the peak coefficients of adhesion
when testing a vehicle fitted with antilock brakes of Category 1.
5.2.2 Gradient
5.2.2.1 The road surface shall be substantially level; a tolerance of ± 1 % average gradient, measured
over a minimum distance of 50 m, is allowed.
5.2.2.2 Type II and Type IIA test site conditions
See Table 2.
Table 2 — Type II and Type IIA test site conditions
Gradient Length of
gradient
% km
Type II 6 6
Type IIA 7 6
5.2.2.3 The parking braking system hill-holding test may be conducted on either an appropriate gradient
or on a level road as specified in 10.3.
5.2.3 Camber
The camber or transverse gradient across the road surface shall not exceed 2 %.
5.3 Ambient conditions
5.3.1 Wind speed
The tests shall be performed when there is no wind liable to affect the results. The wind speed shall not
exceed an average of 5 m/s.
6 © ISO 2003 — All rights reserved

5.3.2 Air temperature
The air temperature shall be recorded in the test report.
6 General requirements
6.1 General test conditions to be followed during determination of braking performance:
a) vehicle speed (see 6.11);
b) without exceeding the maximum permissible control force;
c) engine disconnected or connected (as prescribed);
d) without wheel-locking, except immediately before stopping, unless specifically allowed;
e) without deviation of the vehicle from its course (steering corrections of less than 90° allowed, if not
otherwise specified);
f) loading condition — unless otherwise specified, all tests shall be carried out with the vehicle laden and
unladen.
6.2 During all phases of the following test procedures, any unusual braking performance characteristics or
vehicle behaviour on both (e.g. course deviation or abnormal vibration) shall be observed and reported.
6.3 During the tests with the engine connected on vehicles with a manual gearbox, the clutch may be
disengaged just before the vehicle stops, to avoid the engine stalling.
6.4 Deceleration measurements used in the following test procedures, unless otherwise stated, refer to the
“mean fully developed deceleration” as defined in ECE Regulation 13:1996, Annex 4, paragraph 1.1.2.
6.5 Tests may be carried out under adverse conditions to avoid delays, but with due consideration for
safety. Such adverse conditions shall be reported. Any failed tests under such conditions shall be repeated
under the correct conditions, but not all tests need necessarily be repeated.
6.6 The recommended sequence of the tests is in accordance with Clause 7.
6.7 Full or partial re-tests, after a failed test or to test alternative braking system components, shall again
follow the recommended sequence (see Clause 7), with particular emphasis on the vehicle preparation and
bedding-in procedures.
6.8 Control forces shall be applied rapidly, but without significant overshoot, and shall then be maintained
constant during the stop (if not otherwise specified). An adjustable pressure regulating device should be used.
6.9 Skilled test drivers shall determine the optimum vehicle braking performance without wheel-locking
except immediately before stopping and without course deviation [see 6.1 e) for allowable steering correction]
after appropriately familiarizing themselves with the vehicle braking, steering and suspension systems.
6.10 The brakes are deemed to be cold when the initial temperature of the hottest brake measured on the
disc, on the outside of the drum or on the brake linings is lower than [100] °C before each test stop.
6.11 The speed of the vehicle before actuating the braking system control shall be stabilized at a level not
less than [98] % of the prescribed speed for the test in question unless there is any other overriding
requirement.
6.12 Where a vehicle is so constructed that its maximum speed is lower than that prescribed for any test, the
test shall be performed at the maximum speed of the vehicle.
6.13 Tests with the engine connected shall be carried out in the appropriate gear, defined as the highest
gear normally used at the specified speed without exceeding the manufacturer's recommended maximum
engine speed.
7 Recommended test sequence
7.1 Preparation and static checks and tests
See Table 3.
Table 3 — Preparation and static checks and tests
Relevant Relevant annex
Clause/Subclause and/or paragraph of
No. Test Engine status
of this International ECE Regulation
Standard 13:1996
Preparation (documents, instrumentation,
1 8 § 1 to 2
bedding etc.)
2 Control force vs line pressure 9.1 A4 § 2.1.1
3 Capacity of energy sources Running 9.2 A7 § 2
4 Response time 9.3 A4 § 4
5 Automatic braking 9.4 5.2.1.18.4
6 ABS warning lamp and mode change check 9.5 A13 § 4.1, 4.1.1, 4.1.2
7 Spring braking system 9.6 A8
7.2 Basic performance tests — Unladen
See Table 4.
Table 4 — Basic performance tests — Unladen
Relevant Relevant annex
Clause/Subclause and/or paragraph of
No. Test Engine status
of this International ECE Regulation
Standard 13:1996
1 Type 0 test Disconnected 10.1 A4 § 1.4.2, 2.1.1
2 Type 0 test Connected 10.2 A4 § 1.4.3
Dynamic test of the parking braking system
3 Disconnected 10.4 A4 § 2.2
(if applicable)
4 Parking braking system (hill-holding) Disconnected 10.3 Not prescribed
8 © ISO 2003 — All rights reserved

7.3 Failure tests — Unladen
See Table 5.
Table 5 — Failure tests — Unladen
Relevant Relevant annex
Clause/Subclause and/or paragraph of
No. Test Engine status
of this International ECE Regulation
Standard 13:1996
1 Service braking system failure, type 0 test Disconnected 11.1 A4 § 2.2 or 2.4
2 Failed load-sensing device Disconnected 11.2 A10 § 6
7.4 ABS tests — Unladen
See Table 6.
Table 6 — ABS tests — Unladen
Relevant Relevant annex
Clause/Subclause and/or paragraph of
No. Test Engine status
of this International ECE Regulation
Standard 13:1996
A13 § 4.5,
1 ABS failure Disconnected 12.1
A4 § 2.4.1
2 Determination of k Disconnected 12.2 A13 § app. 2
Hpeak
3 Adhesion utilization on high adhesion Disconnected 12.3 A13 § 5.2
4 Determination of k Disconnected 12.4 A13 § app. 2
Lpeak
5 Adhesion utilization on low adhesion Disconnected 12.4 A13 § 5.2
6 Wheel behaviour tests Disconnected 12.5.2.1 A13 § 5.3.1
7 Transition from high to low adhesion Disconnected 12.5.2.2 A13 § 5.3.2
8 Transition from low to high adhesion Disconnected 12.5.2.3 A13 § 5.3.3
a
9 Split-adhesion test Disconnected 12.5.3 A13 § 5.3.4
a
ABS Category 1 or 2.
7.5 ABS tests — Laden
See Table 7.
Table 7 — ABS tests — Laden
Relevant Relevant annex
Clause/Subclause and/or paragraph of
No. Test Engine status
of this International ECE Regulation
Standard 13:1996
A13 § 4.5,
1 ABS failure Disconnected 13
A4 § 2.4.1
Determination of k
2 Disconnected 13 A13 § app. 2
Hpeak
3 Adhesion utilization on high adhesion Disconnected 13 A13 § 5.2
Determination of k
4 Disconnected 13 A13 § app. 2
Lpeak
5 Adhesion utilization on low adhesion Disconnected 13 A13 § 5.2
6 Wheel behaviour tests Disconnected 13 A13 § 5.3.1
7 Transition from high to low adhesion Disconnected 13 A13 § 5.3.2
8 Transition from low to high adhesion Disconnected 13 A13 § 5.3.3
a
A13 § 5.3.4
9 Split-adhesion test Disconnected 13, 13.1
b
A13 § 5.3.5
10 Energy consumption Disconnected 13.2 A13 § 5.1
a
ABS Category 1 or 2.
b
ABS Category 1.
7.6 Failure tests — Laden
See Table 8.
Table 8 — Failure tests — Laden
Relevant Relevant annex
Clause/Subclause and/or paragraph of
No. Test Engine status
of this International ECE Regulation
Standard 13:1996
1 Service braking system failure, type 0 test Disconnected 14.1 A4 § 2.2 or 2.4
2 Failed load-sensing device Disconnected 14.2 A10 § 6
3 Energy source failure Disconnected 14.3 5.2.1.14
10 © ISO 2003 — All rights reserved

7.7 Basic performance tests — Laden
See Table 9.
Table 9 — Basic performance tests — Laden
Reference to this Reference to ECE R
No. Test Engine status
standard 13:1996
1 Parking braking system (hill-holding) Disconnected 15.1 A4 § 2.3.1-5
2 Dynamic test of the parking braking system Disconnected 15.2 A4 § 2.3.6 or 2.2
3 Type 0 test (plot deceleration vs pressure) Disconnected 15.3 A4 § 1.4.2, 2.1.1
4 Type 0 test Connected 15.4 A4 § 1.4.3
5 Warning device (low pressure warning) Disconnected 15.5 5.2.1.13, 5.2.1.29
6 Capacity of energy storage devices Disconnected 15.6 A7
7 Type II or IIA test Connected 15.7 A4 § 1.6, 1.8 or A5
Type 0 hot performance test (if the service
8 Disconnected 15.7.2.2.3 A4 § 1.6.3
braking system was used for type II test)
9 Type I test Connected 15.8 A4 § 1.5.1
10 Type 0 hot performance (fade) test Disconnected 15.8.4 A4 § 1.5.3.1
8 Vehicle preparation
8.1 Documents and basic date
NOTE The control of the data related to pneumatic braking systems and to ABS (3.2 and 3.3) is also an integral part
of the vehicle preparation.
The vehicle shall be verified based upon the documentation as follows:
a) main technical data according to Annex 2 of ECE Regulation No. 13:1996;
b) piping diagram, layout and list of the elements of the braking system;
c) braking system performance calculation;
d) report/approval of EMC (if vehicle is equipped with an ABS) in accordance with ECE Regulation No. 10 or
Annex B of this International Standard.
8.2 Braking system condition and bedding
8.2.1 The braking system components shall be new, or capable of functioning as new, and within the
vehicle manufacturer's specifications. Individual brake forces should be measured on a roller test bench prior
to the braking performance tests.
8.2.2 The brake linings shall be bedded. Until a uniform procedure is established, the bedding of the service
and parking brake linings should be carried out according to the manufacturer's recommendations.
The brake linings may be regarded as bedded if at least 80 % of their surface is in contact with the brake
drums or discs. Glazed, burned or damaged surfaces are not acceptable.
8.3 Adjustment of braking equipment
Adjustable brake components shall be set according to the vehicle manufacturer's recommendations. Re-
adjustment of the brakes, including automatically adjusted brakes according to the vehicle manufacturer's
recommendations, may be made prior to each specific test.
8.4 Tyre conditions
8.4.1 The tyres shall be inflated to the vehicle manufacturer's recommended pressure levels.
8.4.2 Tyre tread wear should not exceed 50 % of the new condition; totally new tyres should not be used.
8.5 Apparatus and instrumentation
Care should be taken to ensure that instruments and devices needed for testing added to the vehicle braking
equipment do not significantly affect braking system performance.
8.5.1 Additional devices for carrying out the testing of the braking systems
8.5.1.1 Pressure regulating/shut off devices
8.5.1.2 Air reservoir of 0,5 l for trailer control line
8.5.1.3 Air reservoir for simulation of trailer pipe capacity (see 9.2.2)
8.5.1.4 Signalling device (e.g. control lamp) to show functioning of the retarder and, in the case of
integrated retarder control, means of disabling the retarder
8.5.1.5 Towing vehicle for optional drag test(s)
8.5.2 Instrumentation
The test vehicle (and the towing vehicle if appropriate) shall be prepared for testing by the installation of
additional instruments or calibration of the existing standard vehicle instruments, or both, as required.
All the instruments shall be checked to ensure correct functioning, and, with the vehicle stationary on the test
surface, all shall be set.
The instrumentation may include the following.
8.5.2.1 Control force gauge for the service braking system, parking braking system and secondary
braking system (if this system is not combined with either the service or the parking braking system)
8.5.2.2 Decelerometer
8.5.2.3 Speed measuring system or calibrated speedometer
8.5.2.4 Stopping distance measuring means
8.5.2.5 Time measuring means
8.5.2.6 Brake temperature indicating system
8.5.2.7 Application and response time measuring equipment
8.5.2.8 Line pressure gauges/transducers
8.5.2.9 Towing force measuring system
12 © ISO 2003 — All rights reserved

8.5.2.10 Optional instruments, which may include
a) control travel gauges
b) wheel lock indicators
c) steering wheel angle indicator
d) low- to high-adhesion surface transition indicator
8.5.3 Provision for failure simulation
The vehicle shall be equipped with the necessary added devices and piping as agreed with the vehicle
manufacturer, to provide the required failure simulations.
 In the pneumatic part of the braking system, a failure shall correspond to an uncoupled pipe.
 In the hydraulic part of the braking system, a leakage shall be simulated with the brake fluid being
returned to its reservoir.
9 Static tests and checks
9.1 Control force vs line pressure
Produce a graph of increasing line pressure against control force for the service, secondary and parking
braking functions. The graphs should be produced with the vehicle stationary and the system pressure
between the zero and the maximum specified pressure. If the graphs are to be constructed from a series of
individual readings, then at least five readings should be taken, including the threshold value. Care should
also be taken to accurately depict any changes in the force–pressure relationship, taking additional readings if
necessary.
9.2 Capacity of energy sources
9.2.1 Pump-up times
Measure t , the time required for the relative pressure to rise from zero to p , in the least favourably positioned
1 1
braking energy reservoir.
Measure t , the time required for the pressure to rise from zero to p , in the least favourably positioned braking
2 2
energy reservoir, where the vehicle is equipped with no pneumatic reservoir for auxiliary equipment or with
one or more pneumatic reservoirs for the same purpose with a total capacity not exceeding [20] % of the total
capacity of the braking system pneumatic reservoirs.
Measure t , the time required for the relative pressure to rise from zero to p , in the least favourably positioned
3 2
braking energy reservoir, where the vehicle is equipped with one or more pneumatic reservoirs for auxiliary
equipment with a total capacity exceeding [20] % of the total reservoir capacity of the braking system.
9.2.2 Measurement conditions
The speed of the compressor shall be that corresponding to the maximum power of the engine or to that
allowed by the engine governor. The auxiliary equipment reservoirs shall be isolated during the tests for
determination of t and t .
1 2
On motor vehicles capable of towing air-braked trailers, the trailer shall be simulated by a reservoir, attached
to the supply line whose volume V, expressed in litres, is given from the formula:
p ×=VP20
T

max
9.2.3 Basic test (all vehicles)
9.2.3.1 The pump-up time t shall not be greater than [3] min.
9.2.3.2 The pump-up time t shall not be greater than [6] min.
9.2.3.3 Test vehicles capable of towing air-braked trailers shall in this case be tested without the trailer
simulation reservoir.
9.2.4 Basic test (vehicles able to tow air-braked trailers)
9.2.4.1 The pump-up time t shall not be greater than [6] min.
9.2.4.2 The pump-up time t shall not be greater than [9] min.
9.2.5 Additional tests
9.2.5.1 Carry out these tests if the auxiliary equipment reservoir capacity is more than [20] % of the total
capacity of the braking system reservoirs. Independently of t , the pressure in the auxiliary equipment
reservoirs shall reach the pressure(s) specified by the vehicle manufacturer.
9.2.5.2 The pump-up time t for all vehicles shall not be greater than [8] min.
9.2.5.3 The pump-up time t for vehicles capable of towing air-braked trailers shall not be greater than
[11] min. Test vehicles capable of towing air-braked trailers shall in this case be tested without the trailer
simulation reservoir.
9.3 Service braking system — Response time measurement
9.3.1 Test conditions
9.3.1.1 The response time of the service braking system shall be measured at the input port to that
pneumatic actuator which is in the least favourable position.
9.3.1.2 In the case of towing vehicles, the response time shall also be measured at the end of a pipe
[2,5] m long with an internal diameter of [13] mm. This pipe shall be connected to the coupling head of the
control line of the service braking system. A volume of [(385 ± 5)] cm shall be connected to the coupling
head of the supply line.
9.3.1.3 At the beginning of each test, the pressure in all reservoirs shall be equal to the minimum
pressure.
9.3.1.4 The load-sensing device, if fitted, shall be set in the position corresponding to the laden vehicle.
9.3.2 Test procedure
9.3.2.1 Determine the response times to reach [10] % and/or [75] % of the asymptotic pressures, by a
succession of full brake actuations, beginning with the fastest possible control application time and slowing to
an application time of about [0,4] s.
9.3.2.2 Plot the measured response times on a graph. If the figure representing the 100th is five or more,
round the value up to the next higher tenth.
14 © ISO 2003 — All rights reserved

9.3.2.3 The response time to be taken into consideration for the purpose of the test is that corresponding
to an application time of [0,2] s. This response time can be obtained from the graph by linear interpolation
rounded to the nearest tenth of a second.
9.3.2.4 In the case of a semi-trailer tractor, record the length and internal diameter of the coiled flexible
pipes prior to the coupling heads.
9.3.2.5 The time elapsing from the initiation of brake pedal actuation to the moment when the pressure
measured at the pneumatic actuator in the least favourable position (Position A), and at the coupling head of
the pneumatic control line where a pneumatic control line is present (Position B), reaches “x” % of its
asymptotic and respectively final value, shall not exceed the times given in Table 10.
Table 10 — Elapsing time versus percentage of asymptotic pressure
Percentage (x) Time
Position
% s
A 75 0,6
B 10 0,2
B 75 0,4
9.4 Automatic braking
Carry out the following test to check the automatic braking function in the case of a trailer control line failure.
Simulate a break in the trailer control line at the coupling head. Apply the service braking system control
device fully and check that the pressure at the end of the [2,5] m
...