Method and apparatus for measuring the inclination of the wheels of an automobile

A method and apparatus for measuring the inclination of the wheels of an automobile is provided. In accordance with one form of the present invention, there is provided a toe angle detecting device including a pair of detector plates which are normally spaced apart from each other to allow the corresponding wheel of the automobile to be located therebetween and which are pressed against the wheel from both sides when activated to determine the inclination of the wheel with respect to the longitudinal center line of the vehicle, i.e., toe angle of the wheel. In another aspect, a particular link mechanism is provided to interconnect four support members on which the four wheels of the automobile are placed, and the link mechanism is structured to determine the direction of the longitudinal center line of the automobile with respect to the reference line of the link mechanism.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention generally relates to a method and apparatus for testing the 
wheels of a vehicle and in particular to a method and apparatus for 
measuring the inclination of the wheels of a vehicle, such as an 
automobile. More specifically, the present invention relates to a method 
and apparatus for measuring the toe-in/toe out of each of the wheels of a 
vehicle. 
2. Description of the Prior Art 
An automobile generally has four wheels which are arranged in particular 
orientations from various considerations. For example, the front wheels 
are arranged in consideration of such parameters as toe-in/toe-out, 
camber, caster and kingpin angle so as to secure stability in steering 
operation. It is often required to determine these parameters properly in 
order to secure the running stability of an automobile as a whole. Above 
all, proper setting of toe-in/toe-out condition is extremely important 
because this setting is directly related to the operative association 
between the steering wheel and the direction of movement of the 
automobile. 
Although it is well known for one skilled in the art, the toe-in/toe-out 
condition will be explained with reference to FIG. 1 for the sake of 
clarity. The particular arrangement of wheels 2, 2 of an automobile 1 
illustrated in FIG. 2 indicates the toe-in condition, wherein, when viewed 
from above in plan view, the wheels 2, 2 are inclined inwardly with 
respect to the forward direction D of movement of the automobile 1. 
Toe-out is the condition in which the wheels 2, 2 are inclined outwardly, 
i.e., the rear parts of the wheels 2, 2 are closer together than the 
forward parts of the wheels 2, 2 with respect to the forward direction D 
of movement of the automobile 1. For the matter of convenience, here, the 
angle .theta. defined between the forward direction D of movement of the 
automobile 1 and the center plane of each of the wheels 2, as shown in 
FIG. 1, will be referred to as a toe angle. 
In order to set the steering wheel of an automobile properly with respect 
to the direction of advancement of the automobile or the imaginary center 
line extending from the front to the rear, it is required to first measure 
the inclination of each of the right and left wheels with respect to the 
center plane of the automobile, i.e., the toe angle of each of the right 
and left wheels, and to adjust the inclination of each of the left and 
right wheels until they become symmetrically inclined with respect to the 
center plane of the automobile. Any of the prior art methods and apparatus 
for measuring the toe angle was appreciably affected by various measuring 
conditions, including the size and kind of tires encircling and fitting 
the rim of the wheels and the air pressure of each of these tires, and, 
thus, it was extremely difficult to measure the toe angle at high 
accuracy. Among the prior art systems for measuring the toe angle of a 
wheel, there was one using a detector plate which was pressed against the 
outer side surface of a wheel for measuring the toe angle thereof. In this 
case, however, there were variations in the suspension system as a whole 
when the detector plate was pressed against the wheel, so that accurate 
measurement could not be carried out. 
Recently, automobiles having four wheels which are all independently 
suspended have become increasingly popular because of riding comfort and 
reduction of weight. In such automobiles having independently suspended 
front and rear wheels, it is necessary to check and adjust each of the 
four wheels from time to time. 
SUMMARY OF THE INVENTION 
It is therefore a primary object of the present invention to obviate the 
disadvantages of the prior art as described above and to provide an 
improved method and apparatus for measuring the inclination of the wheels 
of a vehicle, such as an automobile, at high accuracy. 
Another object of the present invention is to provide an improved system 
for measuring the toe angle of each of the wheels of a vehicle, such as an 
automobile, at high accuracy and with ease. 
A further object of the present invention is to provide an improved method 
and apparatus capable of measuring the inclination, or toe angle, of each 
of the wheels of a vehicle, such as an automobile, at the same time. 
A still further object of the present invention is to provide an improved 
method and apparatus for measuring the inclination of the wheels of a 
vehicle, such as an automobile, at high accuracy irrespective of the 
difference in model of vehicles. 
A still further object of the present invention is to provide an improved 
method and apparatus for measuring the inclination of the wheels of a 
vehicle, such as an automobile, without being affected by the differing 
conditions of tires encircling and fitting the rim of the wheel. 
A still further object of the present invention is to provide an improved 
system for measuring the inclination, or toe angle, of the wheels of a 
vehicle, such as an automobile, which is sturdy in structure and reliable 
in operation. 
Other objects, advantages and novel features of the present invention will 
become apparent from the following detailed description of the invention 
when considered in conjunction with the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to FIG. 2, there is schematically shown a system for 
measuring the inclination, or toe angle, of the wheels of an automobile 
having four wheels constructed in accordance with one embodiment of the 
present invention. As shown, the toe angle measuring system generally 
comprises a front wheel measuring section 10.sub.A and a rear wheel 
measuring section 10.sub.B, which is spaced apart from the front wheel 
measuring section 10.sub.A by a distance E corresponding to a wheel base 
distance of an automobile to be examined. If desired, the toe angle 
measuring system may be so constructed that the distance E may be 
varyingly set in accordance with the wheel base distance of an automobile 
to be examined as is obvious for those skilled in the art. In the 
illustrated embodiment, since the front and rear toe angle measuring 
sections 10.sub.A and 10.sub.B are identically constructed, like elements 
are designated by like numerals. 
The rear wheel measuring section 10.sub.B is generally defined in a 
rectangular pit extending into the ground from a ground surface G on which 
automobiles run. The rear wheel measuring section 10.sub.B includes a pair 
of support beams 19, 19, which are fixedly attached to the ground surface 
G and extend horizontally in parallel, and a pair of floating tables 
18.sub.R and 18.sub.L, which are movably supported on the pair of beams 
19, 19 along the longitudinal direction thereof with their top surfaces 
generally flush with the ground surface G thereby allowing an automobile 
to be examined to be driven onto the floating plates 18.sub.R and 
18.sub.L. It is so structured that the floating plates 18.sub.R and 
18.sub.L are locked in position when an automobile is driven thereon; 
whereas, these plates 18.sub.R and 18.sub.L are released during toe angle 
measurements. 
Also provided is a pair of rails 11, 11 which are fixed at the bottom of 
the pit and extended horizontally in parallel. On the rails 11, 11 are 
mounted a pair of support plates 12.sub.R, 12.sub.L movable along the 
logitudinal direction of the rails 11, 11, and these support plates 
12.sub.R, 12.sub.L are operatively connected by a connector 13, which is 
commonly called "equalizer". The connector 13 has a center point 13a, 
which is fixed in position, and, thus, the left and right support plates 
12.sub.R, 12.sub.L are controlled to be located symmetrically in position 
with respect to this stationary center point 13a. As is clear from FIG. 2, 
the front wheel measuring section 10.sub.A also includes a similar 
connector 13 having a stationary center point 13a, and, it is to be noted 
that an imaginary straight line H connecting between these stationary 
center points 13a, 13a of front and rear measuring sections 10.sub.A and 
10.sub.B defines a reference straight line for measurement of toe angle. 
With this structure, it is possible to carry out toe angle measurements for 
various automobiles different in wheel separation, and, moreover, just by 
having an automobile set in position as self-driven, it is automatically 
aligned with the reference straight line H. In other words, the 
longitudinal center line of the automobile is aligned with the reference 
straight line H. It is to be noted that here the longitudinal center line 
of an automobile is defined as a straight line extending between the 
center of the front wheel separation (length between the two front wheels) 
and the center of the rear wheel separation. 
As best shown in FIGS. 3 and 4, a turn table 14 in the form of a cross in 
the illustrated embodiment is rotatably mounted on each of the support 
plates 12.sub.R, 12.sub.L via a shaft 43. On the turn table 14 is provided 
a toe angle detecting device including a pair of detector plates 15, 15 
which may be moved closer together or separated away from each other 
through a suitable link mechanism and thus which may be pressed against 
the wheel 2 set on the floating table 18.sub.R from both sides so as to 
detect the inclination of the wheel 2. Each of the detector plates 15, 15 
includes a support member 15c, a pair of spacers 15b, 15b which are 
mounted on the support member 15c on both ends each through a ball bearing 
15d so as to be movable in the vertical direction, and a pair of contact 
plates 15a, 15a which are mounted on the respective spacers 15b, 15b 
through respective ball bearings 15e, 15e to be movable horizontally with 
respect thereto and which are directly brought into contact with the wheel 
2 on both sides thereof. 
With reference to FIGS. 5a and 5b, the operation of the toe angle detecting 
device having the above-described structure will be described. Due to the 
unique structure of the present toe angle detecting device, the pair of 
detector plates 15, 15 may be brought into pressure contact with the wheel 
2 from both sides without imparting any undesired force to the wheel 2 and 
thus to its suspension system. Described more in detail in this respect, 
when the detector plates 15, 15 are pressed against the wheel 2 from both 
sides, pressing forces F, F applied by the respective detector plates 15, 
15 to the wheel 2 are counterbalanced along an imaginary horizontal line 
T. In other words, when the detector plates 15, 15 are moved closer to the 
wheel 2 from both sides, an edge O of the contact plate 15a first comes 
into contact with the corresponding side surface of the wheel 2 and the 
contact plate 15a pivots around the edge O now in contact with the wheel 2 
until the contact plate 15a comes into surface contact with the wheel 2. 
However, the spacer 15b does not follow the movement of the contact plate 
15a, but it moves slidingly along an interface C between the contact plate 
15a and the spacer 15b through the ball bearing 15e thereby causing a 
point Q of application of pressing force to be located at line T. With 
such a structure, even if the pair of detector plates 15, 15 are brought 
into pressure contact with the wheel 2 from both sides, undesired forces 
are prevented from being applied to the wheel and its suspension system, 
thereby allowing to carry out toe angle measurements at high accuracy. 
Furthermore, as shown in FIG. 5b, the present toe angle detecting device is 
also so structured not to be adversely affected by the camber of the wheel 
2, i.e., the inclination of the wheel 2 in the vertical direction. That 
is, in the illustrated embodiment, since the ball bearing 15d is provided 
at the interface C' between the spacer 15b and the support member 15c 
thereby allowing to provide a relative movement therebetween, the point Q' 
of application of pressing force when viewed in the plane vertical to the 
plane of FIG. 5a is also properly located at the line T so that the 
pressing forces are also counterbalanced. This also indicates that no 
undesired forces are applied to the wheel 2. In this manner, according to 
the present invention, since the wheel 2 is pressed from both sides with 
well counterbalanced forces, no undesired forces are applied to the wheel 
2 so that the measurement of the toe angle of the wheel 2 may be carried 
out at high accuracy. 
As best shown in FIG. 4, the detector plate 15 is supported to be pivotal 
around pivot 16a at the top of a stay 16, which extends upright with its 
bottom end slidably mounted on a guide rail 14a. Thus, the detector plate 
15 may be freely pivotted to face upward or downward depending on the 
inclination of the side surface of the wheel 2 against which it is 
pressed. As shown, a pair of such guide rails 14a, 14a are fixedly mounted 
on the cross-shaped turn table 14 and spaced apart from each other and in 
alignment. On the turn table 14 and at the center between the pair of 
detector plates 15, 15 is also provided an air cylinder 17 extending in 
the direction perpendicular to the longitudinal direction of the guide 
rails 14a, 14a. The air cylinder 17 includes a pair of rods 17a, 17b which 
are provided on both ends thereof and which may project and retract in 
opposite directions. Each of the rods 17a, 17b has a pin 17c at its 
forward end and a pair of levers 17b, 17b are pivotally connected to the 
pin 17c at one end with the other end pivotally connected to the stay 16. 
With the above-described structure, when air under pressure is supplied 
from a pressurized air source (not shown) to the air cylinder 17, the 
oppositely arranged rods 17a, 17b project in the opposite directions, 
which, in turn, cause the pair of stays 16, 16 and thus the detector 
plates 15, 15 to move closer together as guided along the guide rails 14a, 
14a through the above-mentioned link mechanism including the levers 17b. 
Thus, with the supply of air under pressure to the air cylinder, the 
detector plates 15, 15 are brought into pressure contact with the wheel 2 
from both sides. 
Regarding the toe angle detecting device for the right-hand wheel 2.sub.R 
as shown in FIG. 4, there is provided a pair of sensors 21, 21, each 
having its tip end in contact with the corresponding one of the pair of 
shafts 17c, 17c, which extend downward from the stay 6 and to which the 
levers 17b, 17b are pivotally connected, respectively, so as to detect the 
amount of movement of the corresponding one of the shafts 17c, 17c. As 
shown in FIG. 2, these sensors 21, 21 are electrically connected to a 
measuring unit 22 to supply detection signals thereto. In the illustrated 
embodiment, the reference condition of each of these sensors 21, 21 is set 
at the condition in which the corresponding detector plate 15 is oriented 
in parallel with the refence straight line H of the present system. Thus, 
the turn table 14 is caused to turn over an angle corresponding to the 
angle defined between the wheel 2 and the system reference straight line 
H, and the corresponding amount of movement of each of the shafts 17c, 17c 
is detected by the respective sensors 21, 21 with the detected information 
being supplied to the measuring unit 22. It is to be noted that in the 
preferred embodiment as illustrated, the values obtained by the sensors 
21, 21 are differentially processed to calculate the angle of inclination 
of the wheel 2 with respect to the system reference straight line H. 
As shown in FIG. 2, the present system includes four such measuring units 
22, one for each wheel 2, and these measuring units 22 are all 
electrically connected to a computer 23, where the values from each of the 
measuring units 22 are suitably processed to determine the inclination of 
each of the wheels 2 with respect to the system reference line H thereby 
calculating the toe angle of each of the wheels 2. The computer 23 is also 
electrically connected to a front wheel toe angle display device 24a and a 
rear wheel toe angle display device 24b, which display the toe angles of 
the wheels 2 thus calculated by the computer 23. Of course, the front and 
rear wheel toe angle display devices 24a and 24b may be integrated, if 
desired. 
In operation, the automobile 1 is driven into the system such that its four 
wheels 2 ride on the respective floating tables 18, which are temporarily 
locked in position. After releasing the floating tables 18 from the locked 
condition, air under pressure is introduced into each of the air cylinders 
17, so that the paired detector plates 15, 15 are moved closer together to 
sandwich the wheel 2 therebetween. In this case, the contact plate 15a of 
detector plate 15 is securely brought into surface contact with the side 
surface of the wheel 2 while producing a relative motion with respect to 
the support member 15 through the spacer 15b as described previously, and 
the turn table 14 is caused to rotate around the shaft 43 over an angle 
corresponding to the angle of inclination of the wheel 2 with respect to 
the system reference line H. The amount of movement of each of the shafts 
17c, 17c is detected by the sensors 21, 21 and the detected values are 
supplied to the measuring unit 22. 
As may be seen in FIG. 4, the wheel 2 typically rides on the floating table 
18 with the center plane C.sub.1 of the wheel 2 being slightly deviated 
from the center plane C.sub.2 of the turn table 14. However, since the 
floating table 18 and support plate 12 are provided to be freely movable 
in predetermined directions, as the detector plates 15, 15 are brought 
into pressure contact with the wheel 2 from both sides as described above, 
the center plane C.sub.1 of the wheel 2 on the floating table 18 is 
automatically brought into alignment with the center plane C.sub.2 of the 
turn table 14 with ease without requiring appreciable driving forces. 
As described above, the amount of movement of each of the shafts 17c, 17c 
detected by the pair of sensors 21, 21 is supplied to the corresponding 
measuring unit 22 where the inclination of the wheel 2 with respect to the 
system reference line H is calculated. The thus calculated inclination of 
each of the wheels 2 is then supplied to the computer 23, where the 
information is processed according to a predetermined program to calculate 
the toe angle of each of the wheels 2, i.e., the inclination of each of 
the wheels 2 with respect to the longitudinal direction D of the 
automobile under test. Then, the thus calculated toe angles are displayed 
at the devices 24a, 24b. Accordingly, while observing the current toe 
angle values displayed, an operator may adjust the inclination of each of 
the wheels 2 until the right and left wheels 2 are set equal in toe angle. 
When so set, the steering wheel is also properly aligned with respect to 
the longitudinal direction D of the automobile under test. 
As a modified structure, the floating tables 18 may be disposed of, if 
desired. In this case, the wheels 2 to be tested are placed directly on 
the support beams 19, 19 which are fixedly attached to the ground surface 
G on both ends. Furthermore, by appropriately defining the system 
reference line, the equalizers 13, 13 may also be disposed of. In this 
case, the rails 11, 11 do not need to be provided as extending from end to 
end in the pit, and they may be provided only partially over the range of 
movement of the support plate 12. In addition, only one sensor 21 may be 
provided for measuring the inclination of each of the wheels 2. Besides, 
an angle sensor (not shown) may be provided on the shaft 16a which 
pivotally connects the detector plate 15 to the stay 16, if desired, in 
which case, the camber of the wheel 2 may be detected at the same time. 
FIG. 6 schematically illustrates another system for measuring the 
inclination of the wheels of an automobile constructed in accordance with 
another embodiment of the present invention. As shown, similarly with the 
previously described system, the present system includes a front wheel 
measuring section 30.sub.A and a rear wheel measuring section 30.sub.B, 
which are also generally defined in the form of the pit in the ground. 
Each of the measuring sections 30 includes a pair of support beams 33, 33, 
which extend horizontally in parallel and spaced apart from each other 
with both their ends fixedly attached to the ground surface G, and a pair 
of floating tables 32.sub.R, 32.sub.L being movable along the pair of 
support beams 33, 33. In each of the measuring sections 30, rails 31 are 
fixedly provided at the bottom of the pit extending horizontally and 
spaced apart from each other. The rail 31 in the front wheel measuring 
section 30.sub.A is in parallel with the rail 31 in the rear wheel 
measuring section 30.sub.B. It is to be noted that one of the rails 31 may 
be provided partially as required and not in a continuous manner as shown. 
On each of the two rails 31, 31 is movably mounted a pair of toe detecting 
devices I.sub.R, I.sub.L which may be used for measuring the inclination 
of the left and right wheels of an automobile under test. As shown in 
detail in FIGS. 7 and 8, each of the toe detecting devices I includes a 
pair of detector plates 35, 35 which may be moved closer together or 
separated away from each other. That is, each of the detector plates 35, 
35 is supported at its center to be pivotal three-dimensionally at the top 
of the stay 36 through a ball joint 37, and the stay 36 rides slideably on 
the rail 31. Between the oppositely arranged detector plates 35, 35 is 
provided an air cylinder 38 fixedly mounted on a slide table 34, which is 
slidable along the rail 31, and perpendicular to the rail 31. A pair of 
rods 38a, 38a are provided in the air cylinder 38 to project or retract in 
opposite directions. The outer ends of the rods 38a, 38a are operatively 
connected to the bottom ends of both of the stays 36, 36 by means of link 
levers 38b. In particular, each lever 38b has its one end pivotally 
connected to the outer end of the rod 38a at 38c and the other end 
pivotally connected to a pivot 38c defined at the bottom of the stay 36 at 
its center. With such a structure, similarly with the previously described 
embodiment, through the operation of the air cylinder 38, the pair of 
oppositely arranged stays 37, 37 and thus the associated detector plates 
35, 35 may be moved closer together or separated away from each other as 
guided by the rail 31, so that the detector plates 35, 35 may be pressed 
against the wheel 2 from both sides, as shown in FIG. 8. 
There is provided a sensor 39 for each of the four toe angle detecting 
devices such that the forward end of the sensor 39 is in contact with one 
end of a support member 35c of the detector plate 35 thereby allowing to 
detect the amount of movement of that portion of the support member 35c, 
and the sensor 39 is electrically connected to an associated measuring 
unit 40 as shown in FIG. 6. It is to be noted that each of the sensors 39 
is so arranged that the reference (zero) condition is established when the 
detector plate 35 is directed perpendicular to the rail 31. Thus, when the 
paired detector plates 35, 35 are pressed against the wheel 2, they are 
moved pivotally three-dimensionally around the ball joint 37 in accordance 
with the angle of inclination of the wheel 2, whereby the sensor 39 
detects the amount of movement of the point in contact thereby supplying a 
detection signal to the measuring unit 40, where the angle of inclination 
of the wheel 2 with respect to the straight line perpendicular to the rail 
31 is calculated. Each of the four measuring units 40, each receiving a 
detection signal from an associated sensor 39, is electrically connected 
to a computer 41. Each of the measuring units 40 is also connected to an 
associated one of other sensors 44a-44d, which are used to detect an 
off-center value of the longitudinal center line of the automobile under 
test from the imaginary reference line H of the measuring system. The 
computer 41 is electrically connected to a front wheel toe angle display 
device 42a including an off-center indicating portion 42c and to a rear 
wheel toe angle display device 42b. 
The operation of the present embodiment is approximately the same as that 
of the previous embodiment. In the previous embodiment, the toe angle 
detecting device I on the turn table 14 as a whole rotates in carrying out 
toe angle measurements; in accordance with the present embodiment, those 
elements which move rotatingly following the inclination of the wheel 2 
are only the pair of detector plates 35, 35. 
As possible modifications of the present embodiment, the sensor 39 may be 
provided more than one for each of the wheels 2 so as to increase the 
level of measuring accuracy. Moreover, an appropriate angle sensor may be 
mounted on the ball joint 37 so as to allow to directly measure the camber 
of the wheel 2 as well. 
FIG. 9 schematically illustrates a still further modification in which the 
sensor 21 is provided one for either side of the wheel 2 thereby allowing 
to detect the inclination of each of the paired detector plates 15, 15 
independently as different from the above-described embodiments wherein 
only one of the paired detector plates 15, 15 is detected for its 
inclination. Such a structure is practically quite advantageous because 
the errors, for example, caused by partial protrusions 2b formed at the 
side of the wheel 2 or tire for indicating the tire manufacturer may be 
minimized in measurement of inclination of the wheel 2. Described more in 
detail in this respect with reference to FIG. 9, in which the left and 
right detector plates 15.sub.L and 15.sub.R are pressed against the wheel 
2 on both sides partly in abutment against the local protrusions 2b, 
designating the angle of inclination of the right detector plate 15.sub.R 
with respect to the system reference line H by .theta..sub.R and the angle 
of inclination of the left detector plate 15.sub.L with respect to the 
reference line H by .theta. .sub.L, the angle of inclination of the center 
plane of the wheel 2 with respect to the reference line H may be expressed 
in the following manner, assuming that the protrusions 2b are formed 
symmetrically on both sides of the wheel 2. 
EQU .theta.=(.theta..sub.R +.theta..sub.L)/2 
Referring now to FIGS. 10-12, there is shown a further embodiment of the 
present invention. FIG. 10 illustrates the overall structure of the system 
for measuring the inclination of the wheels of a four-wheeled automobile 
constructed in accordance with a further embodiment of the present 
invention, in which the main portions are exploded for the purpose of 
illustration and a toe angle detecting device T for each wheel 2 is 
removed. FIG. 11 shows in detail the toe angle detecting device T provided 
for each of the four wheels 2 of an automobile under test with the 
floating table 54 removed. FIG. 12 is a front view showing the structure 
of FIG. 11. As shown in FIG. 10, in a generally rectangular pit P formed 
in the ground surface, there are provided two pairs of rails 53A, 53A and 
53B, 53B extending horizontally in parallel thereby each pair defining a 
front wheel measuring section A and a rear wheel measuring section B. The 
center-to-center distance E between these pairs of rails 53A--53A and 
53B--53B is set equal to the wheel base of an automobile under test. As 
described previously, these pairs of rails 53A--53A and 53B--53B may be so 
structured to be adjustable in spacing thereby allowing to apply for 
various automobiles different in wheel base distance. 
A pair of support plates 54AL, 54AR are movably mounted on the pair of 
rails 53A, 53A therealong and another pair of support plates 54BL, 54BR 
are movably mounted on the pair of rails 53B, 53B. On each of the support 
plates 54 is mounted a toe angle detecting device which will be described 
in detail later. The pair of support plates 54AL, 54AR movably mounted on 
the same pair of rails 53A, 53A are operatively connected through a 
pantagraph type connector 55A, and, similarly, the pair of support plates 
54BL, 54BR are operatively connected through another pantagraph type 
connector 55B. Thus, the distance between the left and right support 
plates may be suitably varied so that the present system may be applied to 
automobiles different in wheel separation. 
Describing the structure of the pantagraph type connector 55A in the front 
wheel measuring section A, horizontal rods 56L and 56R fixedly attached to 
the support plates 54AL and 54AR, respectively, extend in parallel with 
the rails 53A oppositely closer together. First arms 55b, 55b are 
pivotally connected to the forward ends of the horizontal rods 56L, 56R at 
pivots 55a, 55a, respectively, and these first arms 55b, 55b are pivotally 
connected at their forward ends at pivot 55c. A pivot 55d is provided at 
mid-point of each of the first arms 55b, 55b and a pair of second arms 
55e, 55e, which are half as long as the first arms 55b, are pivotally 
connected to the respective pivots 55d, 55d. The pair of second arms 55e, 
55e have their other ends pivotally connected together. With the 
pantagraph type connector 55A constructed as described above, even if the 
distance W between the left and right support plates 54AL and 54AR varies, 
the position of the pivot 55f may be maintained on a straight line h 
defined by connecting the two horizontal rods 56L and 56R. In other words, 
the pivot 55f freely moves along the line h in accordance with changes in 
distance W and is always located at the center of distance W. 
The support plates 54AL, 54AR have shafts 57L, 57R at the center, and 
vertical rods 58L, 58R extending vertically corresponding to the 
longitudinal direction of an automobile under test are pivotally connected 
to the shafts 57L, 57R, respectively. At the forward end of each of the 
vertical rods 58L, 58R, there is provided a scale plate 59L, 59R which may 
be used to indicate the toe angle of the corresponding wheel 2. The scale 
plate 59 is fixedly attached to the vertical rod 58 with the reference 
(zero) point in alignment with the longitudinal direction of the vertical 
rod 58. Thus, even if the vertical rods 58 are inclined with respect to 
the reference center line of the system as shown in FIG. 13, the reference 
(zero) point of the scale plate 59 remains at the longitudinal axis of the 
vertical rod 58. 
The pair of vertical rods 58L, 58R are operatively connected at their 
forward end portions by another pantagraph type connector 60A which is 
similar in structure to the previously described pantagraph type connector 
55A. Described more in detail, horizontal rods 62L, 62R, substantially 
same in length as the previously mentioned horizontal rods 56L, 56R, are 
pivotally connected to the respective vertical rods 58L, 58R at pivots 
61L, 61R, and the pantagraph type connector 60A including a pair of first 
arms 60d, 60d and second arms 60e, 60e, which are all pivotally connected 
via pivots 60a, 60a, 60c, 60d, 60d and 60f. Thus, the pivot 60f is insured 
to always remain at a mid-point between the pivots 60a and 60a. 
The two pantagraph type connectors 55A and 60A are interconnected by a 
synchronizing rod 63A. In this case, the length of the rod 63A is so set 
that all of the pivots 61L, 60a, 60f, 60a and 61R lie in a straight line 
in parallel with the rails 53A. The synchronizing rod 63A has its both 
ends pivotally connected to the pivot 55c of pantagraph 55A and to the 
pivot 60c of pantagraph 60A, so that the corresponding pairs of horizontal 
rods 56L-62L and 56R-62R are synchronized in operation. Thus, even if the 
support plates 54AL, 54AR shift in position during toe angle measurement, 
the distance between the pivots 61L and 61R is always maintained equal to 
the distance W between the support plates 54AL and 54AR and at the same 
time the horizontal rods 62L, 62R are maintained in parallel with the 
rails 53A. That is, the quadrilateral defined by the pivots 57L, 61L, 61R 
and 57R always remain a parallelogram. 
On the other hand, also in the rear wheel measuring section B, a similar 
pantagraph type connector 55B is provided as operatively connected between 
the right and left support plates 54BL, 54BR, and like elements are 
indicated by like numerals. Accordingly, even if the support plates 54BL 
and 54BR are shifted in position sideways along the rails 53B depending on 
the manner of advancement of the automobile to be tested, the 
quadrilateral defined by the pivots 57L, 61L, 61R and 57R always remain to 
be a parallelogram. 
Also provided is a connection rod 64 including a length adjustment section 
64a for operatively coupling the pair of support plates 54AL, 54AR on the 
rails 53A, 53A to the pair of support plates 54BL, 54BR on the rails 53B, 
53B. The connection rod 64 includes a front rod 64A for the front wheel 
measuring section A and a rear rod 64B for the rear wheel measuring 
section B, which are connected by the length adjusting section 64a for 
adjusting the entire length of the connection rod 64. The length adjusting 
section 64a is comprised of a retainer 64a.sub.1 in the form of a cylinder 
with its one end open and a slider 64a.sub.2 which is slidably fitted into 
the retainer 64a.sub.1, and, thus, while maintaining the front and rear 
rods 64A and 64B lying along a straight line, the entire length of the 
connection rod 64 may be suitably adjusted. 
Preferably, the forward end of the front rod 64A is pivotally connected to 
the pantagraph type connector 60A at the pivot 60f and the front rod 64A 
is also pivotally connected to the pivot 55f of the other pantagraph type 
connector 55A. Similarly, the rear rod 64B is pivotally connected to the 
pantagraph type connectors 55B, 60B at pivots 55f, 60f, respectively. With 
the provision of such connection rod 64, the longitudinal center line of 
an automobile to be tested may be always brought into aligenment with the 
lengthwise direction of the connection rod 64 automatically. As is obvious 
from the above description, each of the vertical rods 58 is always 
maintained in parallel with the connection rod 64 through the 
above-mentioned link mechanism so that even in the case in which the 
connection rod 64 is inclined with respect to the longitudinal direction 
as shown in FIGS. 13 and 14, the direction of each of the vertical rods 58 
is always maintained in parallel with the longitudinal center direction of 
the automobile to be tested. As mentioned before, the longitudinal center 
line of an automobile to be tested is defined as a straight line extending 
between the centers of front wheel and rear wheel treads. 
The toe angle detecting device T is mounted on each of the four support 
plates 54 as will be described below. With particular reference to FIGS. 
11 and 12, a turn table 65 formed in the shape of a cross is supported to 
be rotatable around the shaft 57 which is provided at the center of the 
support table 54 and to which the vertical rod 58 is also pivotally 
connected. 
On the cross-shaped turn table 65 is fixedly mounted a pair of guide rails 
66, 66 spaced apart from each other and in alignment, and a pair of 
detector members 67, 67 to be pressed against the wheel 2 from both sides 
for measuring the toe angle thereof are slidably mounted on the guide 
rails 66, 66. In the illustrated embodiment, the detector member 67 
includes a pair of detector plates 67a, 67a spaced apart from each other 
and a support member 67b for supporting the pair of detector plates 67a, 
67a, whereby the pair of detector plates 67a and 67a are brought into 
pressure contact against one side surface of the wheel 2 for measuring the 
toe angle thereof. Between the pair of oppositely arranged detector 
members 67, 67 and oriented perpendicular to the rails 66 is disposed an 
air cylinder 68 having a pair of rods 68a, 68a which project and retract 
in opposite directions. The forward ends of these rods 68a, 68a are 
pivotally connected to link levers 68b, which are pivotally connected to 
the respective ends of the support member 67b at pivots 67c and 68c. Thus, 
when air under pressure is introduced into the air cylinder 68 as supplied 
from a pressurized gas source (not shown), the rods 68a, 68a project in 
the opposite directions, so that the pair of detector members 67, 67 are 
brought closer together as guided by the guide rails 66, 66 thereby 
securely holding the wheel 2 therebetween. It is to be noted that in the 
illustrated embodiment the support beams 69 for supporting thereon the 
wheels 2 in position are held in flush with the ground surface with the 
help of pillars 69a extending upright from the bottom of the pit P. 
As best shown in FIG. 11, a needle 70 is fixedly mounted on the 
cross-shaped turn table 65 with its tip end generally located at the scale 
plate 59 fixedly mounted on the vertical rod 58. Thus, the needle 70 is 
positioned to lie in a longitudinal center plane C.sub.1 of the wheel 2 
when properly held between the pair of detector members 67, 67 under 
pressure. 
In operation, an automobile to be tested is driven by itself into the 
present system such that its four wheels ride on the corresponding support 
beams 69. In this case, as shown in FIGS. 13 and 14, the automobile tends 
to be oriented obliquely with respect to the longitudinal direction of the 
toe angle measuring system I, whereby the longitudinal center line of the 
automobile is inclined with respect to the longitudinal center line of the 
measuring system I. In the present system I, however, due to the 
particular link mechanism, the connection rod 64 becomes always aligned 
with the longitudinal center line of the automobile automatically. 
Besides, as mentioned before, through the unique link mechanism, the 
quadrilateral defined by the points 61, 57, 55f and 60 always remain to be 
a parallelogram. Thus, the vertical rod 58 pivotally connected to the 
support plate 54 on which the toe angle detecting device T is mounted is 
always directed in parallel with the longitudinal center line of the 
automobile so that the zero point on the scale plate 59 indicates the 
direction of the longitudinal center line of the automobile. After placing 
the wheels 2 on the support beams 69, the steering wheel is set to be in 
alignment with the longitudinal center line of the automobile to be 
tested. 
Then, air under pressure is introduced into the air cylinder 68 so that the 
paired detector members 67, 67 are moved closer together thereby being 
brought into pressure contact with the wheel 2 from both sides at the same 
time. In this instance, the turn table 65 is caused to rotate around the 
shaft 57 over an angle corresponding to the degree of inclination of the 
wheel 2 with respect to the longitudinal center line of the automobile. 
Thus, the direction indicated by the needle 70 fixedly mounted on the turn 
table 65 comes into agreement with the direction of longitudinal center 
plane of the wheel 2, and thus a reading on the scale plate 59 indicated 
by the tip end of the needle 70 is the current toe angle of the wheel 2. 
Since the zero point of the scale plate 59 is insured to always indicate 
the direction of the longitudinal center line of the automobile, as 
mentioned above, there is no need to implement correction depending on the 
degree of inclination of the automobile to be tested with respect to the 
reference center line of the measuring system I and the reading on the 
scale plate 59 indicated by the needle 70 directly indicates the true toe 
angle of the wheel 2. In this case, if an operator adjusts the toe angle 
of each of the left and right wheels 2 so as to bring the readings of the 
left and right scale plates 59 indicated by the needles 70 to be 
identical, the steering wheel may be brought into proper alignment with 
the advancing direction of the automobile. 
In the above described embodiment, a pantagraph type connector is provided 
between the left and right support plates; however, in the case where 
automobiles to be tested all have the identical tread separation, such a 
pantagraph connector may be discarded. In this case, it is only necessary 
to have the connection rod 64 pivotally connected to mid points between 
the pivots 61L and 61R and between the pivots 57L and 57R. It should also 
be noted that the pit P may be provided individually for each of the front 
and rear wheel measuring sections A and B, and the rails 53 may be 
provided partly as required. 
FIG. 15 shows a modified structure of the above embodiment. In this case, 
the vertical rod 58 is connected to the shaft 57 which is located at a 
position separated away from the center of the support plate 54 over a 
distance in the direction separating further away from the longitudinal 
center line of the automobile, and the sensor 71 is fixedly mounted on the 
vertical rod 58. The sensor 71 is connected to a display device 72 for 
displaying the value of the detected toe angle. The sensor 71 has a sensor 
rod 71a which extends in the direction perpendicular to the vertical rod 
58. And actuator rod 73 is fixedly mounted on the turn table 65 extending 
forward along the center line C.sub.2 thereof and the tip end of the 
sensor rod 71a is in abutment against the actuator rod 73. The remaining 
structure is similar to that described in the previous embodiment. 
With the above-described modified structure, in the case where the 
automobile to be tested is inclined with respect to the longitudinal 
center line of the measuring system I as shown in FIG. 16, the vertical 
rod 58 is always maintained to be directed in parallel with the 
longitudinal center line of the automobile similarly with the previous 
embodiment. Thus, the amount of movement of the actuator rod 73 detected 
by the sensor 71 fixedly mounted on the vertical rod 58 indicates the 
degree of inclination of the wheel 2 itself without being affected by the 
inclination of the longitudinal center line of the automobile, and, thus, 
the toe angle of each of the wheels 2 may be displayed at the display 
device 72 after simple calculations without requiring to implement any 
correctional procedure. In accordance with the present embodiment, the 
detected toe angle of the wheel 2 may be displayed in digital format with 
a minimum of cost since it only requires a minimum number of sensors and 
simple arithmetic calculations. 
FIGS. 17-19 shows yet another measuring the inclination of the wheel of an 
automobile constructed in accordance with yet another embodiment of the 
present invention. This embodiment is structurally similar to the 
embodiment shown in FIGS. 10-12, and thus like elements are indicated by 
like numerals thereby omitting the repetition of explanation as much as 
possible. As shown in FIG. 17, the present toe angle measuring system is 
also provided in the pit P in the shape of a rectangle and extending into 
the ground from the ground surface on which automobiles run. Unlike the 
previous embodiment, the present system is provided with an indicator rod 
109 for indicating the location of the pivot 55f of the pantagraph type 
connector 55A in the widthwise direction extending along a straight line 
connecting between the pivots 55f and 55c. The indicator rod 109 is formed 
with an elongated slot 109a at one end, and the pivot 55c is loosely 
received in the elongated slot 109a. The other end of the indicator rod 
109 extends beyond the pivot 55fover a predetermined length. In this case, 
due to the unique characteristic of a pantagraph mechanism, the line 
defined between the pivots 55c and 55f is perpendicular to the line 
defined between the pivots 55a and 55a, so that the indicator rod 109 
always extends in the direction perpendicular to the widthwise direction 
even if the center-to-center distance W varies thereby allowing to 
indicate the position of the pivot 55f in the widthwise direction. It is 
to be noted that the above-described structure is identically provided for 
the front and rear wheel measuring sections A and B. 
Also provided are position sensors 110A and 110B for sensing the position 
of the pivots 55f in the widthwise direction of the system I with the tip 
end of the sensing member in abutment against the corresponding indicator 
rod 109. In the present embodiment, the indicator rod 109 is always 
maintained perpendicular to the rails 53A and 53B so that its position 
directly indicates the position of the pivot 55f in the widthwise 
direction. The position sensors 110A and 110B are electrically connected 
to a processor unit 111. As may be recalled, the longitudinal center line 
of the automobile under test becomes always aligned with the straight line 
defined by connecting the pivots 55f, 55f of the front and rear wheel 
measuring sections A and B as indicated by the two-dotted line in FIG. 17. 
Thus, by calculating the inclination of the straight line extending 
between the pivots 55f, 55f of the front and rear wheel measuring sections 
A and B from the respective positions of these two pivots 55f, 55f, the 
inclination of the longitudinal center line of the automobile under test 
may be known. That is, designating an angle from the direction 
perpendicular to the rail 53 by c, detected values of the respective 
position sensors 110A, 110B by a and b, respectively, and the distance 
between the sensors by E' (which may be approximated by the wheel base 
distance E), then the inclination of the longitudinal center line of the 
automobile under test may be expressed in the following manner. 
EQU tan c=(a-b)/E 
Here, the sign of each of the parameters a and b should be changed 
depending on whether the movement of the indicator rod 109 is to the right 
or to the left. 
It is to be noted that the indicator rod 109 does not have to be provided 
at the mid point between the support plates 54AL and 54AR and it may be 
provided at any point therebetween as long as its position is identical 
for the front and rear wheel measuring sections A and B. In such a case, 
the line extending between these two indicator rods 109, 109 disposed at 
points other than mid points does not coincide in position with the 
longitudinal center line of the automobile under test, but its direction 
is parallel to the longitudinal center line of the automobile under test. 
FIGS. 18 and 19 illustrate the toe angle detecting device T provided in the 
system shown in FIG. 17 and this toe angle detecting device T is also 
structurally similar to the one shown in FIGS. 11 and 12 in many respects 
though different numerals are used. In the present embodiment, there is 
also provided a cross-shaped turn table 112 on which is fixedly mounted a 
pair of guide rails 113, 113. And a pair of detector members 114, 114 are 
provided to be slidable along the guide rails 113, 113, respectively, such 
that the detector members 114, 114 may be pressed against the wheel 2 from 
both sides. The detector member 114 also includes a pair of detector 
plates 114a, 114a, which are brought into contact with one side surface of 
the wheel 2, and a support member 114b for supporting the pair of detector 
plates 114a, 114a. An air cylinder 115 is fixedly mounted on the turn 
table 112 and a pair of rods 115a, 115a may project or retract in the 
opposite directions depending on the air pressure inside of the air 
cylinder 115. These rods 115a, 115a are operatively associated with the 
pair of detector members 114, 114 via four link levers 115b, which are 
pivotally connected to the rod 115a and to the detector member 114 on both 
ends, respectively, through pivots 115c and 114c. Thus, as with the 
previous embodiment, when air under pressure is supplied to the air 
cylinder 115, the pair of detector members 114, 114 are moved closer 
together thereby pressing the wheel 2 from both sides. Also as with the 
previous embodiment, support beams 116 for supporting thereon the wheels 2 
in position are provided with both their ends fixed to the ground surface 
and intermediate points supported by pillars 116a which extend upright 
from the bottom of the pit P. Thus, the support beams 116 are generally 
flush with the ground surface GL. 
Also fixedly attached to the turn table 112 is an indicator rod 117 for 
indicating the orientation of the wheel 2 to be examined projecting in the 
direction perpendicular to the lengthwise direction of the guide rails 
113. Thus, the direction of the indicator rod 117 always coincides with 
the direction of the center line C.sub.1 of the wheel 2 sandwiched between 
the pair of detector members 114, 114. Also provided is a position sensor 
118 to sense the position of the indicator rod 117 in contact therewith. 
In the illustrated embodiment, the position sensor 118 is mounted on a 
projection 104a which projects forward from the support plate 54AR and is 
electrically connected to the processor 111. It is so structured that the 
position sensor 118 indicates its zero reference point when the associated 
indicator rod 117 is directed perpendicular to the rails 53. 
The processor 111 is also electrically connected to front and rear wheel 
display devices 119A and 119B, so that when detected inclination 
information for each of the wheels 2 is inputted into the processor 111, 
calculations are carried out by implementing corrections using the 
above-mentioned equation for determing the current inclination of the 
longitudinal center line of the automobile under test to obtain the toe 
angle for each of the wheels 2, which is then displayed at the display 
devices 119A and 119B. In the present embodiment, the front wheel display 
device 119A is structured to display the spoke angle which may be obtained 
by processing each of the toe angle values. 
In operation, an automobile to be tested is first driven into the present 
system to ride on the support beams 116. As shown in FIG. 20, it is often 
the case that the automobile to be tested is directed obliquely so that 
the longitudinal center line of the automobile to be tested is inclined 
with respect to the reference center line of the measuring system I. 
However, in the present system, the longitudinal center line of the 
automobile to be tested is calculated at the processor 111 from the 
information supplied from the position sensors 110A, 110B according to the 
above-noted formula and its information is stored in the processor 111. 
After setting the automobile to be tested properly on the support beams 
116, the steering wheel of the automobile is set at the "straight ahead" 
position. 
Then, air under pressure is supplied into the air cylinder 115 so that the 
paired detection members 114, 114 are moved closer together whereby they 
are pressed against the wheel 2 from both sides. In this case, depending 
on the degree of inclination of the wheel 2, the turn table 112 is caused 
to rotate around the shaft 57. Thus, the indicator rod 117 fixedly mounted 
on the turn table 112 comes to be aligned with the center line C.sub.1 of 
the wheel 2 so that the degree of inclination of the wheel 2 may be 
detected from the degree of inclination of the indicator rod 117. The 
associated position sensor 118 detects the information of the degree of 
inclination of the indicator rod 117 and supplies this information to the 
processor 111, where this information is suitably processed with 
correction being effected using the stored information for the inclination 
of the automobile under test and there is finally obtained the inclination 
of the wheel 2 with respect to the longitudinal center line of the 
automobile under test, or toe angle of the wheel 2. 
Thus the obtained toe angle information is immediately displayed at the 
display devices 119A and 119B so that an operator may suitably adjust the 
orientation of each of the wheels 2 while observing the displayed 
information. In the present embodiment, since the spoke angle is also 
displayed, it may be confirmed that the spoke angle is within a 
predetermined range. 
Referring now to FIG. 21, a still further embodiment of the present 
invention will be described. As shown, the present embodiment of the toe 
angle measuring system also includes a front wheel measuring section A and 
a rear wheel measuring section B. The front wheel measuring section A of 
the present system includes a pair of left and right toe angle detecting 
devices T', T', each of which is so structured to carry out a toe angle 
detecting operation while keeping the wheel to be measured in rotation. On 
the other hand, the rear wheel measuring section B includes a pair of 
support tables 54BL and 54BR which are provided to be movable in the 
horizontal direction and operatively coupled by an equalizer 120. It is to 
be noted that those elements which are identical to those provided in the 
previous embodiments are indicated by like numerals as much as possible. 
The structure of the rotary type toe angle detecting device T' provided in 
the front wheel measuring section A will now be described in detail below. 
As shown in FIG. 21, the device T' includes three rollers 121, 122 and 123 
which are arranged in parallel and supported to be rotatable and on which 
the wheel 2 to be measured rides. Among the three rollers 121-123, the 
center roller 122 is smaller in diameter than the other two front and rear 
rollers 121 and 123, and it is the roller used for detecting the toe angle 
of the wheel 2. The center roller 122 is mounted to rotate around its 
center axis and freely pivot in a plane which is perpendicular to the 
wheel 2. Among the other two rollers, one of them (or front roller 121 in 
the illustrated embodiment) is operatively coupled to a driving source 124 
and this driving roller is driven to rotate at high speed during a toe 
angle measuring operation to cause the wheel 2 to be driven to rotate. The 
toe angle detecting roller 122 is operatively coupled to a servo-motor 
(not shown) which is structured to be controlled in accordance with the 
thrust acting on the toe angle detecting roller 122 in its axial 
direction. Also operatively connected to the roller 122 is a potentiometer 
125 which is then electrically connected to the processor unit 111. Thus, 
if the wheel 2 on the roller 122 is inclined with respect to the axial 
direction of the roller 122, when the roller 121 is driven to rotate to 
cause the wheel 2 to rotate on the roller 122, there is produced a thrust 
acting on the roller 122 in its axial direction and the thrust thus 
produced is converted and amplified into a large power which is then used 
to drive the servo-motor thereby causing the center roller 122 to pivot 
until it comes to the position where there is no thrust. The current 
position of the roller 122 without thrust is then detected by the 
potentiometer 125 and its detection signal is supplied to the processor 
unit 111 as the information indicating the inclination of the wheel 2, 
whereby the toe angle of the wheel 2 is calculated. 
As also shown in FIG. 22, above the rollers 121-123 is disposed a position 
detecting device Q for detecting the position of the wheel 2 riding on the 
rollers 121-123. The position detecting device Q includes a detector 
member 126 provided with a pair of contact rollers 126a, 126a, which are 
brought into rolling contact with one side surface of the wheel 2, and an 
air cylinder 127 having a reciprocatingly movable guide rod 128 having the 
detector member 126 pivotally mounted at its forward end. That is, the 
detector member 126 is pivotal around a pivot 126b in a plane normal to 
the plane of the wheel 2 so that the detector member 126 may pivot 
following the inclination of the wheel 2 with respect to the reference 
center line of the system. 
The left and right detector members 126L and 126R are operatively coupled 
as in the following manner. The detector member 126L or 126R is integrally 
provided with a connector section 126c, which projects forward over a 
predetermined distance, and one end of a horizontal rod 130 is pivotally 
connected to the forward end of the connector section 126c at a pivot 129. 
The other end of the horizontal rod 130 is pivotally connected to the 
other end of the corresponding other horizontal rod 130 at a pivot 131. 
Also provided is a pair of arms 133, 133 whose one ends are pivotally 
connected at pivot 134 and the other ends are pivotally connected to the 
respective horizontal rods 130, 130 at pivots 132, 132. Thus, in effect, 
the rods 130 and arms 133, which are pivotally connected to each other and 
to the connector sections 126c, 126c define a pantagraph type connector. 
As is obvious, the pivot 131 remains located at the mid point between the 
left and right detector members 126L and 126R, or left and right wheels 2 
and 2, and to this pivot 131 is loosely connected one end of a connector 
rod 135 which extends and establishes an operative association between the 
front and rear wheel measuring sections A and B. Described in detail, the 
top end of the connector rod 135 is provided with an elongated slot 135a 
extending along the lengthwise direction of the rod 135, and the pivot 131 
is loosely fitted in this elongated slot 135a. 
Also provided in the vicinity of the pivot 134 is a position sensor 136 for 
detecting the amount of movement of the forward portion of the connector 
rod 135, and this sensor 136 is electrically connected to the processor 
unit 111, whereby the sensor 136 detects the deviation a of the forward 
portion of the connector rod 135 from the reference position and supplies 
this information to the processor unit 111. The reference position or line 
of the present system is defined as a longitudinal center line between the 
left and right toe angle detecting devices T', T'. 
In the rear wheel measuring section B, the toe angle measuring device T as 
described previously is mounted on each of the left and right support 
plates 54BL and 54BR, which are operatively coupled by the equalizer 120. 
As described previously, the equalizer 120 has a stationary center point 
pivot 120a, through which the above-mentioned longitudinal center line of 
the system passes. Thus, the left and right support plates 54BL and 54BR 
are always located equidistantly from the center pivot 120a. The rear end 
of the connector rod 135 is pivotally connected to the stationary pivot 
120a. With such a structure, just by detecting the amount of deviation of 
the forward portion of the connector rod 135 from the longitudinal 
reference line of the system using the position sensor 136, the degree of 
inclination of the longitudinal center line of the automobile under test 
may be measured. In other words, in the above-mentioned equation, it is 
only necessary to determine the inclination c with the parameter b setting 
always equal to zero. 
As an alternative structure, the rotary type toe angle detecting device T' 
may also be provided for the rear wheel measuring section B as well, if 
desired. FIG. 23 shows a still further modification of the above-described 
embodiment, which includes the front and rear wheel measuring sections A 
and B, which are spaced apart in the longitudinal direction twice the 
wheel base distance of an automobile to be tested, and an intermediate 
section 137, which is comprised of pair of left and right support plates 
operatively coupled by an equalizer. In this embodiment, the automobile to 
be tested is first located between the intermediate section 137 and the 
rear wheel measuring section B to carry out toe angle measurements for the 
rear wheels, and, then, the automobile to be tested is moved to ride on 
the front wheel measuring section A and the intermediate section 137 to 
carry out toe angle measurements for the front wheels. 
While the above provides a full and complete disclosure of the preferred 
embodiments of the present invention, various modifications, alternate 
constructions and equivalents may be employed without departing from the 
true spirit and scope of the invention. Therefore, the above description 
and illustration should not be construed as limiting the scope of the 
invention, which is defined by the appended claims.