Road vehicles -- Compressed air braking systems for towed vehicles including those with electronic braking control functions -- Test procedures

ISO 7634:2007 specifies the test procedures for testing the operational performance requirements of towed vehicles of Category O (full trailers, semi-trailers, and centre-axle trailers) as defined in Annex 7 of the UN-ECE Consolidated Resolution on the Construction of Vehicles (R. E. 3). This includes vehicles fitted with compressed air braking systems (with and without an antilock braking system or an electronically controlled braking system), in accordance with the UN-ECE Regulation 13, 09 series of amendments, supplements 1 to 6. Test methods covering lock actuators are not included.

Véhicules routiers -- Dispositifs de freinage à air comprimé pour véhicules remorqués, y compris ceux avec fonctions de commande de freinage électroniques -- Modes opératoires d'essai

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Published
Publication Date
30-May-2007
Current Stage
9093 - International Standard confirmed
Start Date
17-Jun-2021
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INTERNATIONAL ISO
STANDARD 7634
Third edition
2007-06-01
Road vehicles — Compressed air braking
systems for towed vehicles including
those with electronic braking control
functions — Test procedures
Véhicules routiers — Dispositifs de freinage à air comprimé pour
véhicules remorqués, y compris ceux avec fonctions de commande de
freinage électroniques — Modes opératoires d'essai
Reference number
ISO 7634:2007(E)
ISO 2007
---------------------- Page: 1 ----------------------
ISO 7634:2007(E)
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© ISO 2007

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ii © ISO 2007 – All rights reserved
---------------------- Page: 2 ----------------------
ISO 7634:2007(E)
Contents Page

Foreword............................................................................................................................................................. v

1 Scope ..................................................................................................................................................... 1

2 Normative references ........................................................................................................................... 1

3 Terms and definitions........................................................................................................................... 2

4 Symbols ................................................................................................................................................. 3

5 Test site conditions .............................................................................................................................. 7

5.1 Test site ................................................................................................................................................. 7

5.2 Road surface condition........................................................................................................................ 7

5.3 Ambient conditions .............................................................................................................................. 8

6 General requirements........................................................................................................................... 8

7 Recommended sequence of tests....................................................................................................... 9

7.1 Preparation and static checks and tests............................................................................................ 9

7.2 Basic performance tests – unladen .................................................................................................. 10

7.3 Antilock braking system/electronically controlled braking system (ABS/EBS) tests —

unladen ................................................................................................................................................ 10

7.4 Basic performance tests — Laden.................................................................................................... 10

8 Vehicle preparation............................................................................................................................. 11

8.1 Documents and basic data ................................................................................................................ 11

8.2 Braking system condition and bedding ........................................................................................... 11

8.3 Adjustment of braking equipment .................................................................................................... 11

8.4 Tyre conditions ................................................................................................................................... 12

8.5 Towing vehicles .................................................................................................................................. 12

8.6 Instrumentation — General................................................................................................................ 12

8.7 Provision for failure simulation......................................................................................................... 12

8.8 Loading condition............................................................................................................................... 13

8.9 Additional vehicle to tow the combination of normal towing vehicle and test trailer ................. 13

8.10 Additional instrumentation for ABS equipped trailers ................................................................... 13

8.11 Additional instrumentation for trailer with an electric control line ............................................... 13

9 Energy storage capacity test............................................................................................................. 14

9.1 Test conditions ................................................................................................................................... 14

9.2 Test procedure .................................................................................................................................... 14

9.3 Test requirement................................................................................................................................. 14

9.4 Presentation of results....................................................................................................................... 14

10 Service braking system — Response time measurement.............................................................. 14

10.1 General................................................................................................................................................. 14

10.2 Towing vehicle simulator................................................................................................................... 15

10.3 Test conditions ................................................................................................................................... 15

10.4 Test procedure .................................................................................................................................... 15

10.5 Presentation of results....................................................................................................................... 16

11 Automatic braking .............................................................................................................................. 16

12 Brake defect and failure warning signals......................................................................................... 16

12.1 Antilock braking system warning signal..........................................................................................16

12.2 EBS warning signal check ................................................................................................................. 16

13 Tests on trailers equipped with spring brake actuators................................................................. 16

13.1 Initial conditions ................................................................................................................................. 16

13.2 Energy depletion test ......................................................................................................................... 17

© ISO 2007 – All rights reserved iii
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ISO 7634:2007(E)

13.3 Spring brake actuation test................................................................................................................ 17

13.4 Auxiliary release system check......................................................................................................... 17

14 Dynamometer tests (alternative to vehicle tests) ............................................................................ 17

14.1 General ................................................................................................................................................. 17

14.2 Alternative type I tests (fade test for trailers of categories O and O )........................................ 17

2 3

14.3 Alternative type III tests (fade test for category O trailers)........................................................... 19

15 Transfer of results of type I or type III tests to other vehicles ....................................................... 21

15.1 General ................................................................................................................................................. 21

15.2 Presentation of results ....................................................................................................................... 22

16 Control failure of load-sensing device/function — Stationary test................................................ 23

17 Auxiliary equipment failure................................................................................................................ 24

18 Basic performance tests — Unladen ................................................................................................ 24

18.1 Type O test (Service braking system cold brake effectiveness).................................................... 24

19 Antilock braking system/electronically controlled braking system (ABS/EBS) tests —

Unladen ................................................................................................................................................ 26

19.1 Determination of adhesion utilization on high adhesion surface.................................................. 26

19.2 Determination of the peak coefficient of adhesion on the high adhesion surface ...................... 27

19.3 Wheel behaviour ................................................................................................................................. 30

19.4 Split adhesion tests ............................................................................................................................ 30

19.5 Energy consumption of the antilock braking system (on a high adhesion surface)................... 31

19.6 Antilock braking system failure......................................................................................................... 33

19.7 Additional tests on trailers equipped with EBS............................................................................... 33

20 Basic performance tests — Laden .................................................................................................... 34

20.1 Parking braking system tests ............................................................................................................ 34

20.2 Type O test (Service braking system cold brake effectiveness).................................................... 37

20.3 Control failure of load-sensing device/function — Road test ........................................................ 37

20.4 Type I test (fade test for trailers of categories O and O )............................................................. 37

2 3

20.5 Type III test (fade test for vehicles of category O )......................................................................... 40

Annex A (normative) Description of test vehicle, axle or brake .................................................................. 44

Annex B (normative) Test report..................................................................................................................... 47

Annex C (informative) Figures......................................................................................................................... 50

Bibliography ..................................................................................................................................................... 54

iv © ISO 2007 – All rights reserved
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ISO 7634:2007(E)
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 7634 was prepared by Technical Committee ISO/TC 22, Road vehicles, Subcommittee SC 2, Braking

systems and equipment.

This third edition cancels and replaces the second edition (ISO 7634:2003), which has been technically

revised.
© ISO 2007 – All rights reserved v
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INTERNATIONAL STANDARD ISO 7634:2007(E)
Road vehicles — Compressed air braking systems for towed
vehicles including those with electronic braking control
functions — Test procedures
1 Scope

This International Standard specifies the test procedures for testing the operational performance requirements

of towed vehicles of Category O (full trailers, semi-trailers, and centre-axle trailers) as defined in Annex 7 of

the UN-ECE Consolidated Resolution on the Construction of Vehicles (R. E. 3). This includes vehicles fitted

with compressed air braking systems (with and without an antilock braking system or an electronically

controlled braking system), in accordance with UN-ECE Regulation No. 13, 09 series of amendments,

supplements 1 to 6. Test methods covering lock actuators are not included.

The values 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, Road vehicles — Masses — Vocabulary and codes

ISO 3583, Road vehicles — Pressure test connection for compressed-air pneumatic braking equipment

ISO 3833, Road vehicles — Types — Terms and definitions

ISO 7638-1, Road vehicles — Connectors for the electrical connection of towing and towed vehicles — Part 1:

Connectors for braking systems and running gear of vehicles with 24 V nominal supply voltage

ISO 7638-2, Road vehicles — Connectors for the electrical connection of towing and towed vehicles — Part 2:

Connectors for braking systems and running gear of vehicles with 12 V nominal supply voltage

ISO 11992 (all parts), Road vehicles — Interchange of digital information on electrical connections between

towing and towed vehicles
ISO/PAS 12158, Road vehicles — Braking systems — Temperature measuring methods

UN-ECE Regulation No. 13, Uniform provisions concerning the approval of vehicles with regard to braking.

NOTE Regulation 13 is periodically updated through amendments and supplements, with this standard having been

prepared in accordance with the 09 series of amendments including supplements 1 to 6. When using this standard care

should be taken to ensure that changes have not subsequently occurred that effect the test methods or values given.

© ISO 2007 – All rights reserved 1
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ISO 7634:2007(E)
3 Terms and definitions

For the purposes of this International Standard, the terms and definitions given in ISO 611, ISO 1176 and

ISO 3833 and the following apply.
3.1
pneumatic (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

NOTE Figures C.1 and C.2 show examples of typical full trailer and semi-trailer air braking systems.

3.2
electronic braking system
EBS

braking system in which the control is generated and processed as an electrical signal in the control

transmission

NOTE Electrical output signals control devices which produce actuation forces from stored pneumatic energy.

3.3
categories of ABS
3.3.1
Category A:

ABS system which meets all the requirements of UN-ECE Regulation No. 13, Annex 13

3.3.2
Category B:

ABS system which meets all the requirements of UN-ECE Regulation No. 13, Annex 13, except paragraph

6.3.2 (no braking rate on split-adhesion surface is prescribed)
3.4
wheel control
3.4.1
directly controlled wheel

wheel whose braking force is modulated according to data provided by at least its own sensor

3.4.2
indirectly controlled wheel

wheel whose braking force is modulated according to data provided by the sensor(s) of other wheel(s)

NOTE ABS systems 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.

3.5
ABS – full cycling

state of the antilock system in which the brake force is repeatedly modulated to prevent the directly controlled

wheels from locking

NOTE Brake applications where modulation only occurs during the stop are not considered to meet this definition.

3.6
laden trailer

trailer laden so as to reach its total maximum design mass (ISO 1176 code: ISO-M07)

2 © ISO 2007 – All rights reserved
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ISO 7634:2007(E)

NOTE In the case of semi-trailers and centre-axle trailers being road tested, the loading may be such that the

maximum design load per axle (ISO 1176 code: ISO-M11) is reached without loading the fifth wheel for semi-trailers or the

mechanical coupling for centre-axle trailers. However, for the testing of the parking braking system (see 20.1) the loading

on the fifth wheel or mechanical coupling in the case of semi-trailer and centre-axle trailers is included.

3.7
unladen trailer

trailer at its shipping mass (ISO 1176 code: ISO-M05) minus spare wheel(s) and spare wheel carrier(s) and

other optional items, plus the mass of the required instrumentation (see 8.6, 8.10 and 8.11)

3.8
electric control line

electrical connection between an electronic braking system equipped power-driven vehicle and an electronic

braking system equipped trailer which provides the braking control function to the trailer

NOTE It comprises the electrical wiring and connector and includes the parts for data communication and the

electrical energy supply for the trailer control transmission.
4 Symbols

For the purposes of this International Standard, the symbols given in Table 1 apply.

Table 1 — Symbols
Symbol used
Symbols Description in ECE Reg.
Unit
No. 13
C Nm Brake camshaft input torque C
C ′ Nm Converted camshaft input torque (reference paragraph 15.2.3.4)
C Nm Threshold camshaft input torque (i.e. minimum camshaft torque C
o o
necessary to produce a measurable braking torque)
Nm Technically admissible camshaft input torque at a pressure in the
adm
brake actuator lower than the maximum pressure (reference
paragraph 15.2.3.3 )
C Nm Maximum technically admissible camshaft input torque C
max max
E E
m Wheelbase
E m Distance between kingpin and centre of axle or axles of semi-trailer E
R R
(or distance between drawbar coupling and centre of axle or axles of
centre-axle trailer)
e Index to indicate the reference axle e
Adhesion utilization of the trailer
ε ε
ε ε value on the high adhesion surface ε
H H
ε ε value on the low adhesion surface ε
L L
F Average output thrust of one brake actuator at a pressure p
A A
corresponding to p = 0,65 MPa (= 6,5 bar)
N Converted brake actuator output thrust (to allow for difference
between p and p ) (reference paragraph 15.2.3.4)
Ae A
F N Threshold brake actuator output thrust (i.e. minimum output thrust
necessary to produce a measurable braking torque)
© ISO 2007 – All rights reserved 3
---------------------- Page: 8 ----------------------
ISO 7634:2007(E)
Table 1 (continued)
Symbol used
Symbols Unit Description in ECE Reg.
No. 13
N Maximum technically admissible brake actuator output thrust at a
Aadm
pressure in the brake actuator lower than the maximum pressure
(reference paragraph 15.2.3.3)
N Maximum technically admissible brake actuator output thrust
Amax
F N Braking force at the periphery of the wheel(s) (if no other indication is T
given)
F N Braking force resulting at the periphery of the wheel(s) for hot braking T
F N Sum of braking forces resulting at the periphery of all wheels of the T
BaR R
trailer for hot braking
F N Braking force at the periphery of the wheel(s) for heating the brake(s)
F N Sum of braking forces at the periphery of all wheels of the trailer T
BR R
F F
N Braking force of the trailer with the antilock system inoperative
bR bR
F N Braking force of the trailer with the antilock system operative F
bRAL bRAL
F N F on split adhesion surface
bRALS bRAL
F Maximum value of F F
bRmax bR bRmax
F N Total normal reaction of road surface on those axles of the motor F
Cd Cd
vehicle and trailer combination which are both unbraked and driven
F N Total normal static reaction of road surface on those axles of the F
Cnd Cnd
motor vehicle and trailer combination which are unbraked yet non-
driven
F N Normal dynamic reaction of road surface on the trailer axles, with the F
dyn dyn
antilock system operative
F N F on front axle of a full trailer F
fdyn dyn fdyn
F P F
N Normal static reaction of road surface on axle i
i i, i
F F on axle i of a full trailer F
idyn dyn idyn
F N Normal static reaction at a tractor fifth wheel on semi-trailer kingpin, or
at mechanical coupling of a towing vehicle on the drawbar of a centre-
axle trailer
F D
N Longitudinal force on a mechanical coupling
F N Total normal reaction of road surface on all wheels of the motor P F
M M, M
(towing) vehicle
F N Total normal static reaction of road surface on the unbraked, driven F
Md Md
axles of the motor (towing) vehicle
F F
N Total normal static reaction of road surface on the unbraked, non-
Mnd Mnd
driven axles of the motor (towing) vehicle

F N Total normal static reaction of road surface on all wheels of the trailer P F

R R, R
F N Normal dynamic reaction of road surface on all braked wheels of the P
Rb 2
trailer
F N Normal dynamic reaction of road surface on all wheels of a semi- F F
Rdyn idyn, Rdyn
trailer or a centre-axle trailer
4 © ISO 2007 – All rights reserved
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ISO 7634:2007(E)
Table 1 (continued)
Symbol used
Symbols Unit Description in ECE Reg.
No. 13
F P
N Total normal static reaction of road surface on all unbraked wheels of
Ru 1
the trailer
F N F on rear axle of a full trailer
rdyn dyn
F N Rolling resistance of the motor (towing) vehicle: F
WM WM
0,01 F + 0,015 F
Mnd Md
g m/s² Acceleration due to gravity G, g
h m Height of drawbar (hinge point on trailer) h
D D
h m Height of fifth wheel coupling (kingpin) h h
K K, S
h m Height of centre of gravity of the trailer h
R R
k Coefficient of adhesion between tyre and road k
K K
Correction factor, semi-trailer laden
c c
k k-factor of one front axle k
f f
k k-factor for high adhesion surface k
H H
k k
k-factor for low adhesion surface
L L
k Peak k-factor k
peak peak
k k-factor of one rear axle k
r r
k k-factor of the trailer k
R R
I m Lever length I
P P kg Mass of the individual motor vehicle / trailer P
M, R
p bar Pressure in brake actuator(s)
p bar Pressure in the trailer control line p
m m
p bar Pressure in the energy reservoir(s) of the service braking system of
res
the trailer, when the control device of the service braking system is
fully applied for the first time
p′ bar Pressure in the energy reservoir(s) of the service braking system of
res
the trailer, when the control device of the service braking system has
been fully applied 9 times
p bar Pressure in the trailer supply line
R R
mm Dynamic tyre rolling radius
R mm Static tyre radius
r R
mm Normal effective radius of brake drum or disc
S mm Stroke of brake actuator
S mm Stroke of brake actuator at which output thrust is 0,9 F s
Ap A p
S mm Automatic brake adjustment device re-adjustment stroke (at an s
re-adjust re-adjust
actuator pressure of 1 bar)
© ISO 2007 – All rights reserved 5
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ISO 7634:2007(E)
Table 1 (continued)
Symbol used
Symbols Unit Description in ECE Reg.
No. 13
t t
s Time interval
t Mean value of t t
m m
t s Minimum value of t t
min min
v km/h Vehicle speed v
v km/h Velocity of cooling air flow v
air air
v km/h Final vehicle speed at the end of braking test v
f 2
v km/h Vehicle speed at beginning of braking test v, v
s 1
z Braking rate [total braking force of vehicle divided by the normal static z
reaction of road surface (can be calculated for the whole vehicle, a
single axle or a single wheel)]
z Achieved braking rate
z Achieved braking rate of an axle, evaluated by calculation
z z + M
Achieved braking rate of the vehicle combination
aC R
z Achieved braking rate of trailer, evaluated by calculation
z Calculated braking rate of vehicle with hot brakes
BaR
z z
Braking rate of vehicle combination with the trailer only braked and
C C
the antilock system inoperative (towing vehicle engine disconnected)
z Braking rate of vehicle combination with the trailer only braked and z
CAL CAL
antilock system operative
z z on the split-adhesion surface
CALS CAL
z Maximum value of z z
Cmax C Cmax
z Braking rate resulting from F
hae Bae
z Braking rate resulting from F
he Bhe
Braking rate for one wheel
z Hot braking rate for one wheel
paW
z Braking rate for heating the brakes of the trailer
phR
Trailer service braking rate
z Braking rate of the trailer obtained by calculation from z
RAL CAL
z z on the high friction surface z
RALH RAL RALH
z z on the low friction surface z
RALL RAL RALL
z z on the split-surface z
RALS RAL RALS
z R
Total braking rate as a result of rolling resistance
In accordance with ISO 31-3:1992. Quantities and units-Part Mechanics.
See UN-ECE Regulation No. 13 Annex 10, diagram 4B.
Value is 0,01 (see UN-ECE Regulation No. 13 Annex 4, sub-clause 1.4.4.3).
6 © ISO 2007 – All rights reserved
---------------------- Page: 11 ----------------------
ISO 7634:2007(E)
NOTE For some calculations, additional indices as listed below may be used:
⎯ subscripts etc., indicate axles no. 1, no. 2, no. 3, etc., respectively;
1, 2, 3,
⎯ I or III indicate the fade test type (type I or III test respectively);

⎯ e indicates the reference axle for the calculation of the values for the axle i;

⎯ or indicates a front or rear axle.
f r
5 Test site conditions
5.1 Test site

The test site should 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 of sufficient length to allow for poor braking performance and sufficient width to allow

for poor directional stability under braking.
5.2 Road surface condition
5.2.1 Surface

5.2.1.1 The test area shall be a dry, smooth, hard-surface free of loose material providing a peak

coefficient of adhesion (k ) of about [0,8].
peak

5.2.1.2 Additionally, for the testing of trailer(s) equipped with an antilock braking system of

...

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