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Ref. No.: IS0 / R 612 - 1967 (E)
IS0
I NT ERN AT I O N AL O RG A N IZAT I O N FO R STA NP AR D I2 AT I O N
IS0 RECOMMENDATION
R 612
DIMENSIONS OF MOTOR VEHICLES AND THEIR TRAILERS
DESIGNATIONS AND DEFINITIONS
1st EDITION
Au g uçt 1967
COPYRIGHT RESERVED
The copyright of IS0 Recommendations and IS0 Standards
belongs to IS0 Member Bodies. Reproduction of these
documents, in any country, may be authorized therefore only
by the national standards organization of that country, being
a member of ISO.
For each individual country the oniy valid standard is the national standard of that country.
Printed in Switzerland
Also issued in French and Russian. Copies to be obtained through the national standards organizations.
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BRIEF HISTORY
The IS0 Recommendation R 612, Dimensions of Motor Vehicles and their Trailers
-Designations and DeJinitions, was drawn up by Technical Committee ISO/TC 22,
Automobiles, the Secretariat of which is held by the Association Française de Normalisation
(AFNOR).
Work on this question by the Technical Committee began in 1958 and led, in 1963,
to the adoption of a Draft IS0 Recommendation.
In August 1963, this Draft IS0 Recommendation (No. 586) was circulated to all the
IS0 Member Bodies for enquiry. It was approved, subject to a few modifications of an
editorial nature, by the following Member Bodies :
Argentina Italy Spain
Belgium Japan Sweden
Chile Korea, Rep. of Switzerland
Czechoslovakia Netherlands United Kingdom
France
Poland Yugoslavia
Greece Portugal
Hungary Romania
Two Member Bodies opposed the approval of the Draft:
Germany
U.S.A.
The Draft IS0 Recommendation was then submitted by correspondence to the IS0
Council, which decided, in August 1967, to accept it as an IS0 RECOMMENDATION.
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CONTENTS
Page
Introduction. . 3
I. List of terms to be defined . 4
II. Designations and definitions . 5
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iSO/ R612-1967(E)
IS0 Recommendation R 612 August 1967
DIMENSIONS OF MOTOR VEHICLES AND THEIR TRAILERS
DESIGNATIONS AND DEFINITIONS
INTRODUCTION
(1) The purpose of this IS0 Recommendation is to give the designations and definitions relating
to dimensions of motor vehicles and their trailers.
This Recommendation is not concerned with stating methods of measurement or with
specifying the units to be used in reporting the results, nor is it concerned with the accuracy
required or the order of magnitude of the dimensions specified.
Unless otherwise stated in regard to one or more of the items mentioned below, it should be
understood that :
(a) The supporting surface is horizontal.
Consequently, lengths and widths are measured on the horizontal plane, heights on the
vertical plane.
(b) The total weight of the vehicle is the maximum permissible weight, the load being spread
according to the manufacturer’s instructions.
(c) The tyres are inflated to the pressure corresponding to the maximum permissible weight
of the vehicle.
(4 The vehicle is stationary. Its wheels and articulated elements are in positions correspond-
ing to movement in a straight line.
(e) The definitions of the dimensions apply to vehicles which are new from the factory and
normally equipped.
(3) The definitions given in regard to dimensions of features relating to vehicles result in the
measurement of lengths, angles, and dihedral angles. It is to be remembered that:
(a) The distance from a point A to a plane P is the length of a segment AB, B being the base
of the perpendicular to A lowered on to plane P.
The distance from a point A to a straight line D is the length of a segment AB, B being the
point of intersection of the straight line D and the plane P perpendicular to D, guided by A.
In both cases, the segment AB is the shortest distance from A to the straight line D or to
the plane P.
(b) An angle is specified in plane geometry, if the two straight lines from the same point
which form it, or bound it, are defined.
(c) The angle between a line and a plane is the acute angle formed by the straight line with its
projection on to that plane.
(d) The value of a dihedral angle is defined, when its edge and its faces (semi-planes) are
defined, or if it is stated as follows:
acute or obtuse dihedral angle formed by two intersecting planes.
(e) A straight line in a space, passing through a given point and orthogonal to another
straight line or to a direction, is not defined by this specification.
(f) The expression “ mid plane of the wheel ” occurs in a number of definitions.
This is the plane equidistant from the inner edges of the rim.
(g) Lastly, the so-called “ longitudinal ” plane of symmetry of a vehicle is defined under
Term 1. It is designated by the expression “ longitudinal plane of symmetry ”.
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IS0 / R 612 - 1967 (E)
I. LIST OF TERMS TO BE DEFINED
1. Longitudinal plane of symmetry
2. Track
3. Wheel base
4. Height of chassis above ground
5. Length of chassis for bodywork (vehicle without cab)
6. Length of chassis behind cab (vehicle with cab)
7. Bodywork length
8. Ground clearance
9. Ground clearance on a convex surface
10. Ramp angle
11. Vehicle length
12. Drawgear length
13. Drawbar length
14. Position of towing attachment
15. Vehicle width
16. Vehicle height
17. Maximum internal dimensions of body (goods vehicles)
18. Usable dimensions of body
19. Front overhang angle
20. Rear overhang angle
21. Front overhang
22. Rear overhang
23. Wheel rake
24. Toe-in
25. Axle-pin rake
26. Set (or lateral inclination of the swivelling axis of the axle-pin)
27. Swivelling radius
28. Vertical travel of wheel
29. Lift
30. Turning locks
31. Turning clearance circles
32. Tyre radius under load
33. Theoretical running radius oi tyre
34. Wheel offset
35. Distance between centre lines of twin tyres
36. Fifth wheel lead
37. Semi-trailer wheel base
38. Height of seat of loaded vehicle
39. Front fitting radius of semi-trailer
40. Lower fitting radius of semi-trailer
41. Distance between king pin axis and front end of prime mover
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IS0 / R 612 - 1967 (E)
II. DESIGNATIONS AND DEFINITIONS
1. Longitudinal plane of symmetry
For each wheel, the vertical plane passing through the axis of the axle-pin cuts the mid plane
of the wheel following a straight line D. The latter meets the supporting surface of the vehicle
at one point.
Let A and B be two points defined in this way, which correspond to two wheels, both of
which are either steering or powered wheels, situated respectively at both ends of the same
real or imaginary axle, then, the so-called " longitudinal " plane of symmetry of the vehicle
is the vertical plane P perpendicular to and bisecting the segment AB (Fig. 1).
A
FIG. 1
2. Track
Consider a point A or B defined in the first paragraph of Term 1 and the distance AH or
BH from this point to the longitudinal plane of symmetry (Fig. 3).
The track a corresponding to a real or imaginary axle is the sum of the two distances AH
and BH in relation to the two wheels connected to this axle (Fig. 2).
Twin wheels (Fig. 4)
The straight line D is the intersection of the mid plane of the twin wheels and of the vertical
plane passing through the axis of the axle-pin.
The mid plane of the twin wheels is equidistant from the inner edge of one wheel and the outer
edge of the other.
NOTE. - Practical briefdefinition. In the case of two single wheels corresponding to the same real or imaginary
axle, the track is represented by the distance between the mid points of the traces left by the wheels on the
supporting surface.
H B
f\
A Y
--
I
O t IJ
t >lu c It
a
FIG. 2 FIG. 3 FIG. 4
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IS0 / R 612 - 1967 (E)
3. Wheel base
The distance a between the perpendicular lines dropped on to the longitudinal plane of
symmetry of the vehicle from the previously defined points A or B corresponding to two
consecutive wheels situated on the same side of the vehicle (Fig. 5 and Fig. 6).
B
H.
A H
m
+B
A
H
FIG. 5
NOTE. - This definition may give rise to different values for right and left wheel bases corresponding to
two consecutive axles.
Vehicles with three or more axles (Fig. 7 and Fig. 8)
The wheel bases between consecutive wheels are indicated, going from the foremost to the
rearmost wheel; the total wheel base for right or for left is the sum of these distances.
a a
-
FIG. 6 RG. 7
FIG. 8
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IS0 / R 612 - 1967 (E)
4. Height of chassis above ground
The distance a from the ground to the horizontal line perpendicular to the longitudinal plane
of symmetry of the vehicle and touching the upper surface of the chassis. This distance is
considered in particular, when measured at the front, at the rear of the chassis and at the
centre of the largest wheel base (Fig. 9).
I
FIG. 9
NOTE. - The height of the chassis above the ground should be determined not only with the vehicle loaded
to its maximum total permissible weight, but also with the vehicle unladen.
5.
Length of chassis for bodywork (vehicle without cab)
The distance a between two vertical planes A and B perpendicular to the longitudinal plane of
symmetry of the vehicle (Fig. 10).
Plane A passing through the front end of the foremost pedal, when this is depressed to the
maximum amount.
Plane B touching the rear end of the chassis.
FIG. 10
6. Length of chassis behind cab (vehicle with cab)
The distance a between the vertical plane A’ perpendicular to the longitudinal plane of
symmetry touching the rear wall of the cab, and plane B defined under Term 5 (Fig. 11).
I
FIG. 11
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IS0 / R 612 - 1967 (E)
7. Bodywork length
Goods vehicle (Fig. 12). The distance a between plane A defined under Term 5 and the outer
rear end of the bodywork B'.
FIG. 12
Private car (Fig. 13). The length of the car.
a a
I
FIG. 13
NOTE. - The bodywork length does not include lashing hooks, towing attachments of trailers, rear registra-
tion number plates, bumpers, etc., unless these are an integral part of the bodywork.
8. Ground clearance
Y
The ground clearance is the maximum height (on the small side) of a rectangle, the plane of
which is vertical and perpendicular to the longitudinal plane of symmetry of the vehicle
dividing this rectangle into two equal parts (Fig. 14).
It should be possible to move this rectangle beneath the vehicle without touching any part
of the latter.
The lower part of the brake drums should not be considered in measuring the ground
clearance.
FIG. 14
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IS0 / R 612 - 1967 (E)
9. Ground clearance on a convex surface
Consider a cylinder of 8 m radius whose axis is perpendicular to the longitudinal plan of
symmetry of a vehicle resting on that cylinder.
The ground clearance a on a convex surface is the difference between the radii of two cylinders,
one as defined above and the other being a cylinder on the same axis as the first one and
tangential to the lowest part of the vehicle (Fig. 15).
FIG. 15
10. Ramp angle
Consider the dihedral angle a, the edge of which is perpendicular to the longitudinal plane
of symmetry of the vehicle and on whose faces the wheels of the vehicle may rest without
the latter touching the edge; the size of the angle is the smallest angle which meets this
condition.
The ramp angle is the acute dihedral angle p, supplement of angle a. (Fig. 16).
FIG. 16
11. Vehicle length
Automobile vehicles
The distance a between two vertical planes perpendicular to the longitudinal plane of sym-
metry of the vehicle and touching the front and rear of the latter respectively (Fig. 17).
+-
I wi
+
I
, FIG. 17
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IS0 / R 612 - 1987 (E)
All parts of the vehicle, including any parts projecting to front or rear (towing-hooks,
bumpers, etc.) are contained between these two planes.
Trailers
The lengths with and without drawgear a and a' are stated (Fig. IS), the latter being placed
in brackets, e.g. 5500 (3700), taking into account the above
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