ISO 23365:2022

Heavy commercial vehicles and buses — Definitions of properties for the determination of suspension kinematic and compliance characteristics

This document applies to heavy vehicles—that is, to commercial vehicles and buses as defined in ISO 3833—that are covered by the categories M3, N2, N3, O3, and O4 of ECE and EC vehicle regulations. These categories pertain to trucks and trailers with maximum weights above 3,5 tonnes and to buses with maximum weights above 5 tonnes. Vehicle suspension kinematic and compliance (K&C) properties that impact vehicle stability and dynamic behaviour are described in this document and common methods of measurement are outlined. These methods are applicable to heavy vehicles. The measurements are performed on a single unit and typically one or two axles at a time. This document will define or reference the key suspension kinematic and compliance parameters necessary for characterizing and simulating vehicle suspension performance. These parameters also provide system-level descriptions of quasi-static behaviour that can be cascaded into subsystem and component performance targets. The suspension variables required for determining suspension characterization of one vehicle end, i.e. for a single axle or for multiple axles inter-related through suspension configuration (for example, walking-beam), are provided. Metrics pertaining to the chassis connection between the front and rear suspensions are not included. Some typical methods of measurement will be discussed, however detail on how the measurements are executed is not within the scope of this document.

Véhicules utilitaires lourds et autobus — Définitions des propriétés pour la détermination des caractéristiques cinématiques et de conformité des suspensions

General Information

• Status: Published
• Publication Date: 14-Jul-2022
• ICS: 43.080.01 - Commercial vehicles in general
• Technical Committee: ISO/TC 22/SC 33 - Vehicle dynamics and chassis components
• Drafting Committee: ISO/TC 22/SC 33/WG 6 - Vehicle dynamics of heavy commercial vehicles and buses
• Current Stage: 6060 - International Standard published
• Start Date: 15-Jul-2022
• Due Date: 24-Jan-2023
• Completion Date: 15-Jul-2022

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 23365
First edition
2022-07
Heavy commercial vehicles and
buses — Definitions of properties
for the determination of suspension
kinematic and compliance
characteristics
Véhicules utilitaires lourds et autobus — Définitions des propriétés
pour la détermination des caractéristiques cinématiques et de
conformité des suspensions
Reference number
ISO 23365:2022(E)
© ISO 2022

---------------------- Page: 1 ----------------------
ISO 23365:2022(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2022
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
  © ISO 2022 – All rights reserved

---------------------- Page: 2 ----------------------
ISO 23365:2022(E)
Contents  Page
Foreword . vi
Introduction .vii
1  Scope . 1
2  Normative references . 1
3  Terms and definitions . 1
4  Principle . 4
5 Variables . 5
5.1 Reference system . 5
5.2 Variables to be determined . 5
5.2.1 Vehicle geometry . 5
5.2.2 Motion variables . 5
5.2.3 Forces and moments . 5
5.2.4 Steering geometry . 6
5.2.5 Kinematics . 6
5.2.6 Compliances . 7
5.2.7 Ride and roll stiffness . 7
5.2.8 Force reactions . . 8
6  Measuring equipment . 8
6.1 Measurement accuracy . 8
6.2 Derived variable accuracy . 9
7  Suspension parameter measurement guidance . 9
7.1 Steering geometry . 9
7.1.1 Steering ratio . 9
7.1.2 Overall steering ratio (i ) . 10
S
7.1.3 Ackermann error . . . 11
7.1.4 Inclination angle (ε ). 11
W
7.1.5 Camber angle (ε ) . 11
V
7.1.6 Castor angle (τ) . 11
7.1.7 Castor offset at ground (n ) . 11
k
7.1.8 Castor offset at wheel centre (n ) .12
τ
7.1.9 Steering-axis inclination angle (σ).12
7.1.10 Steering-axis offset at ground (r ) .12
k
7.1.11 Steering-axis offset at wheel centre (r ) .12
σ
7.1.12 Normal steering-axis offset at ground (q ) .13
T
7.1.13 Normal steering axis offset at wheel centre (q ) .13
W
7.1.14 Scrub radius (r) . 13
7.2 Kinematics . 14
7.2.1 General . 14
7.2.2 Ride track change (b ) .15
z
7.2.3 Ride track change gradient (b ’) . 15
z
7.2.4 Ride steer (δ ) . 16
z
7.2.5 Ride steer gradient (δ ’) . 16
z
7.2.6 Total ride toe (δ ) . 16
z(R-L)
7.2.7 Total ride toe gradient (δ ’) . 16
z(R-L)
7.2.8 Ride camber (ε ) . 16
Vz
7.2.9 Ride camber gradient (ε ’) . 16
Vz
7.2.10 Ride castor (τ ) . 17
z
7.2.11 Ride castor gradient (τ ’) . 17
z
7.2.12 Roll steer (δδ ) . 17
ϕϕ
V
iii
© ISO 2022 – All rights reserved

---------------------- Page: 3 ----------------------
ISO 23365:2022(E)
′′
7.2.13 Roll steer gradient (δδ ) . 17
ϕϕ
V
7.2.14 Roll camber (εε ) . 17
Vϕϕ
V
′
7.2.15 Roll camber gradient (εε ) . 17
Vϕϕ
V
7.3 Compliances . 18
7.3.1 General . 18

′
7.3.2 Longitudinal force compliance, with suspension torque (x ) . 18
F
X

′
7.3.3 Longitudinal force compliance, without suspension torque (x ) . 19
F
XW

′
7.3.4 Longitudinal force camber compliance, with suspension torque (εε ) . 19
VF
X

′
7.3.5 Longitudinal force camber compliance, without suspension torque (εε ) . 19
VF
XW

′
7.3.6 Longitudinal force steer compliance, with suspension torque (δδ ) .20
F
X

′
7.3.7 Longitudinal force steer compliance, without suspension torque (δδ ) .20
F
XW

′
7.3.8 Longitudinal force windup compliance, with suspension torque (ττ ) .20
F
X

′
7.3.9 Longitudinal force windup compliance, without suspension torque (ττ ) .20
F
XW

′
7.3.10 Lateral force compliance at the wheel centre ( y ) . 21
F
YW

′
7.3.11 Lateral force compliance at the contact centre ( y ) . 21
F
Y

′
7.3.12 Lateral force camber compliance (εε ) . 21
VF
Y

′
7.3.13 Lateral force steer compliance (δδ ) . 21
F
Y

′
7.3.14 Aligning moment camber compliance (εε ) .22
VM
Z

′
7.3.15 Aligning moment steer compliance (δδ ) .22
M
Z
7.4 Ride and roll stiffness .22
7.4.1 General .22
7.4.2 Ride rate (K ) . 22
Z
7.4.3 Suspension ride rate (K ) . 23
ZK
7.4.4 Roll stiffness (K ) .23
ϕϕ
V
7.4.5 Suspension roll stiffness (K ) . . 23
ϕϕ
K
7.4.6 Auxiliary roll stiffness (K ) . 24
ϕϕ ,aux
V
7.4.7 Auxiliary suspension roll stiffness (K ) . 24
ϕϕ ,aux
K
7.4.8 Vertical displacement tandem axle load redistribution stiffness (K ) . 24
tz
7.4.9 Vertical suspension displacement tandem axle load redistribution stiffness
(K ) . 25
tzK
7.4.10 Tandem axle twist stiffness (K ) . 25
φt
7.4.11 Tandem axle suspension twist stiffness (K ) . 25
φtK
7.4.12 Tyre normal stiffness (K ) . 25
ZT
7.5 Force reactions . 25


′
7.5.1 Anti-squat and anti-dive force gradient (F ) . 25
ZF
X
iv
  © ISO 2022 – All rights reserved

---------------------- Page: 4 ----------------------
ISO 23365:2022(E)


′
7.5.2 Jacking force gradient (F ) . 26
ZF
Y

′
7.5.3 Longitudinal force tandem axle load redistribution gradient (W ) .26
DtF
XT
8  Data presentation .26
8.1 Steering ratio . 26
8.2 Kinematic properties .30
8.3 Compliance properties . 31
8.4 Ride and roll stiffness properties . 32
8.5 Force reaction properties . 32
Annex A (informative) Mathematic fit of steering ratio as a function of steering wheel angle .34
Bibliography .35
v
© ISO 2022 – All rights reserved

---------------------- Page: 5 ----------------------
ISO 23365:2022(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.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
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. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/
iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 22, Road vehicles, Subcommittee SC 33,
Vehicle dynamics and chassis components.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
vi
  © ISO 2022 – All rights reserved

---------------------- Page: 6 ----------------------
ISO 23365:2022(E)
Introduction
The dynamic behaviour of a road vehicle is a very important aspect of active vehicle safety. Any given
vehicle, together with its driver and the prevailing environment, constitutes a closed-loop system that
is unique. The task of evaluating the dynamic behaviour is therefore, very difficult since the significant
interaction of these driver-vehicle-environment elements are each complex in themselves. A complete
and accurate description of the behaviour of the road vehicle shall necessarily involve information
obtained from a number of different tests.
Static properties of the vehicle and its systems can have an important impact on the vehicle dynamic
behaviour and a driver’s or automation’s ability to generate the desired motion. Test conditions have a
strong influence on test results. Therefore, only vehicle dynamic and static properties obtained under
virtually identical test conditions are comparable to one another.
Since this test method quantifies only one small part of the complete vehicle handling characteristics,
the results of these tests can only be considered significant for a correspondingly small part of the
overall dynamic behaviour.
Moreover, insufficient knowledge is available concerning the relationship between overall vehicle
dynamic properties and accident avoidance. A substantial amount of work is necessary to acquire
sufficient and reliable data on the correlation between accident avoidance and vehicle dynamic
properties in general and the results of these tests in particular. Consequently, it is important for any
application of this test method for regulation purposes the proven correlation between test results and
accident statistics.
vii
© ISO 2022 – All rights reserved

---------------------- Page: 7 ----------------------
INTERNATIONAL STANDARD ISO 23365:2022(E)
Heavy commercial vehicles and buses — Definitions of
properties for the determination of suspension kinematic
and compliance characteristics
1  Scope
This document applies to heavy vehicles—that is, to commercial vehicles and buses as defined in
ISO 3833—that are covered by the categories M3, N2, N3, O3, and O4 of ECE and EC vehicle regulations.
These categories pertain to trucks and trailers with maximum weights above 3,5 tonnes and to buses
with maximum weights above 5 tonnes.
Vehicle suspension kinematic and compliance (K&C) properties that impact vehicle stability and
dynamic behaviour are described in this document and common methods of measurement are outlined.
These methods are applicable to heavy vehicles. The measurements are performed on a single unit and
typically one or two axles at a time.
This document will define or reference the key suspension kinematic and compliance parameters
necessary for characterizing and simulating vehicle suspension performance. These parameters also
provide system-level descriptions of quasi-static behaviour that can be cascaded into subsystem and
component performance targets. The suspension variables required for determining suspension
characterization of one vehicle end, i.e. for a single axle or for multiple axles inter-related through
suspension configuration (for example, walking-beam), are provided. Metrics pertaining to the
chassis connection between the front and rear suspensions are not included. Some typical methods of
measurement will be discussed, however detail on how the measurements are executed is not within
the scope of this document.
2  Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements 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 8855, Road vehicles — Vehicle dynamics and road-holding ability — Vocabulary
ISO 15037-2, Road vehicles — Vehicle dynamics test methods — Part 2: General conditions for heavy
vehicles and buses
3  Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 8855, ISO 15037-2 and the
following apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
side view swing centre
point in a plane parallel to the X -Z plane that intersects the wheel centre and locates the instantaneous
V V
centre of rotation of the wheel centre resulting from a displacement in the Z direction
V
1
© ISO 2022 – All rights reserved

---------------------- Page: 8 ----------------------
ISO 23365:2022(E)
3.2
side view swing arm angle
angle from a horizontal line parallel to the X -Z plane that intersects the side view swing centre (3.1)
V V
and the line that intersects the side view swing centre and wheel centre
3.3
longitudinal force compliance, with suspension torque

′
x
F
X
rate of change of the wheel centre displacement in the X direction with respect to a force exerted on
V
the geometric centre of the tyre contact patch in the X direction
V
3.4
longitudinal force compliance, without suspension torque

′
x
F
XW
rate of change of the wheel centre displacement in the X direction with respect to a force exerted on
V
the wheel centre in the X direction
V
3.5
longitudinal force camber compliance, with suspension torque

′
ε
VF
X
rate of change of camber angle with respect to a force exerted on the geometric centre of the tyre
contact patch in the X direction
V
3.6
longitudinal force camber compliance, without suspension torque

′
ε
VF
XW
rate of change of camber angle with respect to a force exerted on the wheel centre in the X direction
V
3.7
longitudinal force steer compliance, with suspension torque

′
δ
F
X
rate of change of steer angle with respect to a force exerted on the geometric centre of the tyre contact
patch in the X direction
V
3.8
longitudinal force steer compliance, without suspension torque

′
δ
F
XW
rate of change of steer angle with respect to a force exerted on the wheel centre in the X direction
V
3.9
longitudinal force windup compliance, with suspension torque

′
τ
F
X
rate of change of the axle or hub assembly angle about the Y axis with respect to a force exerted on the
V
geometric centre of the tyre contact patch in the X direction
V
3.10
longitudinal force windup compliance, without suspension torque

′
τ
F
XW
rate of change of the axle or hub assembly angle about the Y axis with respect to a force exerted on the
V
wheel centre in the X direction
V
2
  © ISO 2022 – All rights reserved

---------------------- Page: 9 ----------------------
ISO 23365:2022(E)
3.11
lateral force compliance at the wheel centre

′
y
F
YW
rate of change of wheel centre displacement in the Y direction with respect to a force exerted on the
V
geometric centre of the tyre contact patch in the Y direction
V
3.12
lateral force compliance at the contact centre

′
y
F
Y
rate of change of geometric centre of the tyre contact patch displacement in the Y direction with
V
respect to a force exerted on the geometric centre of the tyre contact patch in the Y direction
V
3.13
lateral force camber compliance

′
ε
VF
Y
rate of change of camber angle with respect to a force exerted on the geometric centre of the tyre
contact patch in the Y direction
V
3.14
lateral force steer compliance

′
δ
F
Y
rate of change of steer angle with respect to a force exerted on the geometric centre of the tyre contact
patch in the Y direction
V
3.15
aligning moment camber compliance

′
ε
VM
Z
rate of change of camber angle with respect to a moment exerted on the tyre contact patch about the Z
V
axis
3.16
aligning moment steer compliance

′
δ
M
Z
rate of change of steer angle with respect to a moment exerted on the tyre contact patch about the Z
V
axis
3.17
auxiliary roll stiffness
K
ϕ ,aux
V
contribution to roll stiffness beyond that which results from ride rate and symmetric vertical tyre
contact patch-to-body displacement
3.18
auxiliary suspension roll stiffness
K
ϕ ,aux
K
contribution to suspension roll stiffness beyond that which results from suspension ride rate and
symmetric vertical wheel-to-body displacement
3.19
total ride toe
δ
z(R-L)
change in the difference of the left steer angle from the right steer angle observed in ride mode (3.22)
3
© ISO 2022 – All rights reserved

---------------------- Page: 10 ----------------------
ISO 23365:2022(E)
3.20
total ride toe gradient
δ ’
z(R-L)
differential of total ride toe (3.19) with suspension travel as observed in ride mode (3.22)
3.21
wheel pad
surface of the kinematic and compliance measurement facility that supports each tyre contact patch
and is typically capable of applying forces at the geometric centre of the tyre contact patch in the X and
Y directions, moments at the tyre contact patch about the Z axis, and optionally displacements in the
Z direction
Note 1 to entry: The wheel pads are assumed to represent the ground plane. If the vehicle sprung mass is not
rolled relative to the wheel pads, it can be assumed that the intermediate axis system and vehicle axis system
coincide.
3.22
ride mode
motion of vehicle suspension produced by near-equal Z displacements of the wheel centres on a single
T
axle relative to the vehicle body, with wheel pad (3.21) X and Y forces and Z moments controlled to as
T

near-zero as practicable, and preferably with the change in M held as near to zero as practicable
X
3.23
roll mode

motion of single axle produced by a pure roll moment, M , resulting from equal and opposite change in
X
the forces applied to the left and right tyre contact centres of each axle
...