The present invention relates to a suspension system for a vehicle, particularly an automotive or motor vehicle.

WO 96/34775 describes that,'in many instances, the space available for a vehicle suspension system is very limited. A particular problem is raised where the suspension needs to occupy limited area in order to maximise available cabin space. WO 96/34775 responds to this problem by providing a suspension assembly which includes an upper arm joined to a lower arm by an upright member. The arms are pivotally attached to the vehicle frame so as to be pivotable about axes which extend generally transverse of the vehicle.

Furthermore, packaging of a suspension system is also challenging for a so-called "narrow track" vehicle. "Track" can be defined as the largest transverse distance between individual wheels in set(s) of wheels, for example the front and rear sets of wheels of a four wheel vehicle. A narrow track vehicle typically has track, or distance between a set of wheels, of less than 1000 mm and potentially lower than 500 mm, dimensions less than transverse dimensions of the vehicle body frame. In this case, not only is there a challenge in packaging the suspension system but also a challenge in achieving required suspension performance, especially in a vehicle with steered wheels where the steering
system must also be packaged within the vehicle.

US Patent No. 7097187 describes a suspension system for a four wheel motorcycle type vehicle. The narrow width of the motorcycle does not allow for positioning of an independent suspension system between the two front wheels. The motorcycle is therefore provided with an outer wheel mounted suspension system. With the two front wheels located very close together, the steering arrangement is clearly of a motorcycle type quite distinct from that, for example of a four wheel vehicle. In such case at least, the steering system of US Patent No. 7097187 would not provide the required steering system geometry and stability.

It is an object of the present invention to provide a suspension system for a vehicle which is more easily packaged and also provides better performance, particularly for steered four wheel vehicles, than previous suspension systems.

With this object in view, the present invention provides a suspension system for a vehicle having a chassis and comprising:

a pair of wheels, each wheel of said pair of wheels being rotatably mounted to an axle connected to the vehicle chassis and steerable by a steering system comprising a steering mechanism connected to said wheel; and
a suspension means of double arm type extending longitudinally for each wheel of said pair of wheels wherein each suspension means comprises vertically disposed upper and lower arms extending parallel to a longitudinal axis or plane of the vehicle, said upper and lower arms being pivotally connected by a vertical link to form a suspension assembly located outboard of each wheel and wheel track for the vehicle and wherein said vertical link is operatively connected to said steering mechanism by a linkage arrangement overlapping said wheel. The vertical link defines a steering axis for the vehicle located outboard of each said wheel.

The vehicle suspension system provides each wheel with an independent suspension. The suspension system may be implemented in a vehicle, irrespective of the number of wheels and in front, rear or intermediate position. Conveniently, however, the pair of wheels is the front pair of wheels of a four wheel vehicle.

The steering system, which "overlaps" the wheels, conveniently includes a steering mechanism which extends horizontally in a direction between each wheel of said pair of wheels at above wheel height.

A range of steering systems could be selected but a particularly convenient steering system involves a rack and pinion mechanism connected to a steering column and steering wheel, links or linkages between these steering systems allowing steering of a vehicle correspondent with driver operation of the steering wheel. A rack and pinion steering mechanism is typically elongate and cylindrical or beam-like in configuration extending in a horizontal direction. However, different steering systems and steering mechanisms could be employed in accordance with the invention. For example, half rack and bell crank or recirculating ball screw with

ball crank mechanisms could be selected in place of a rack and pinion steering mechanism.

Conveniently, the upper and lower arms of the suspension system are pivotally connected to the vertical links through joints such as ball joints. The elongate steering mechanism is conveniently pivotally connected to each said vertical link by the linkage arrangement, for example through a tie rod and steering arm of the vertical link located above wheel height for each wheel. In a convenient arrangement, a tie rod corresponds, and overlaps, with each wheel and the tie rods have a divergent disposition.

The above described steering system advantageously has a steering axis inclined to a longitudinal vertical plane and outboard of each wheel. In the above mentioned steering system, steering axis is visualized through a line joining the at least two pivotal connections of each vertical link. One pivotal connection would be of vertical link to upper arm of the suspension system and the other pivotal connection would be of vertical link to lower arm of the suspension system. This - steering axis would extend upward in rearward and outboard direction with respect to the longitudinal vertical plane of the vehicle. This provides the required steering geometry and stability.

The suspension system preferably, and advantageously, is designed to achieve zero wheel track change and camber change during operation of the suspension system, which minimizes tyre wear.

The assembly of upper and lower arms and vertical links, as so far described, is pivotably mounted to a chassis of the vehicle. Each arm of the suspension system may be independently connected by pivot joints to the vehicle chassis. Each arm is then allowed to pivot about a pivot axis of a joint, forming an independent suspension, the orientation of this pivot axis defining caster, wheel camber, roll centre height and toe change during wheel vertical travel, i.e suspension operation.

For a desired roll centre height of the vehicle, a pivot axis of the lower arm of the suspension assembly is inclined inward, frontward and upward with respect to a

transverse axis of the vehicle and a pivot axis of said upper arm is inclined upward, rearward and downward with respect to said transverse axis of said vehicle.

The location and orientation of pivot axis/axes, in co-operation where necessary with steering hardpoints are selected, advantageously during the vehicle design phase, to achieve desired suspension characteristics including camber and toe change. For example, where zero camber change is desired, the pivot axis of each pivot joint for an arm is preferably designed to be set substantially parallel to the pivot axis of each corresponding joint for the other arm and also to a transverse axis of the vehicle, which is an axis perpendicular to the above-mentioned longitudinal plane of the vehicle.

Typically, the pivot joints will be designed to achieve zero camber change during vertical wheel travel when driving as this reduces type wear.

Pivot axes for pivot joints for both upper and lower arms of suspension means for both left and right wheels, typically front wheels, in this case are desirably coaxial and horizontal. Put another way, the pivot joints for the upper arms desirably have a common horizontal pivot axis. The pivot joints for the lower arms also desirably have a common horizontal pivot axis. This may be varied if desired.

Wheel toe and camber change under suspension operation is defined by inclining pivot axis (axes) to the transverse axis of the vehicle. Caster is dependent on arm length and its mounting pivot location. Thus the desired caster change or constant caster requirement can be satisfied by selecting appropriate pivot locations for given arm lengths.
The axles on which wheels are mounted are conveniently stub axle(s) extending inboard and which may be integrated with respective vertical links connecting the lower and upper arms of the suspension system.

A suspension means for a wheel comprises a shock absorption system including damping members located outboard of the wheel. The suspension system may incorporate different elastic or spring members for shock absorption, these members typically being supplemented by damping members which are located

outboard of the wheels in the arrangement described here. Either the upper or lower arms of the suspension system may be connected by a bar/tube. Such a bar/tube may be a cylindrical bar/tube and is used as a vehicle stabiliser acting as an anti-roll device.

However, if the cylindrical bar is mounted to the vehicle body frame or chassis to prevent rotation of the bar with respect to the body frame, it is a torsion bar spring. The bar/tube, when acting as a torsion bar, may supplement or substitute other elastic or spring members for the suspension system. The elastic or spring members may be provided in the form of coil springs. Damping members may be hydraulic cylinders. The bar need not be cylindrical in cross-section.

In such embodiments, a first suspension means is provided for one wheel of a pair of wheels and a second suspension means is provided for a second wheel of said pair of wheels, each wheel of said pair of wheels being located on an opposed side of said longitudinal axis of said vehicle and a bar or tube connects a longitudinally extending arm of said first suspension means with a corresponding longitudinal extending arm of said second suspension means to resist relative rotation of the suspension means with respect to each other.

The bar or tube may connect longitudinally extending upper and/or lower arms of each suspension means to resist relative rotation of each suspension means with respect to each other. The bar or tube may be pivotably mounted on a vehicle body frame or said vehicle chassis and connected, through linkages, to longitudinally extending upper and/or lower arms of each suspension means to resist relative rotation of each suspension means with respect to each other.

The bar or tube may be a torsion bar spring fixed to a vehicle body frame or said vehicle chassis to resist relative rotation of each suspension means with respect to said vehicle body frame or vehicle chassis.

Each of the upper and lower arms of the suspension system for a wheel may have varying geometry, based on strength and packaging requirements and may include open frame or solid members. The upper arms may be wedge shaped, for example, triangular wedge shape. The lower arms may be provided more in the form of bars, perhaps in arcuate shape in the form of angled or curved bars, tending

to angle or curve - with an arcuate shape in a forward direction - toward a centre longitudinal axis of the vehicle in order to accommodate wheel movement when employed for steered wheel application. Ideally, the dimensions of each of the upper and lower arms, particularly in longitudinal direction, are chosen such that the suspension system provides desired caster and trail change. The dimensions, particularly longitudinal dimensions, may be adjusted to vary caster and trail change if desired.

The suspension system of the present invention may be applied to a range of automotive vehicle types, whether two, three, four or more wheeler vehicles. In addition, the suspension system may be applied to both powered and un-powered automotive vehicles and irrespective of whether the automotive vehicle wheels are steered or un-steered. Particular advantage is achieved for vehicles with steered wheels where the suspension system is readily packaged together with the steering system.

The above described vehicle suspension system has a number of advantages over conventional lateral mounted suspension systems. First, the suspension system should enable significant weight reduction in body/frame structure. Second, mounting the suspension system outboard of the vehicle wheel(s) facilitates shockloads transferred to wider span of the vehicle body structure and close to the out longitudinal members of the chassis. Third, the suspension system can provide better anti-dive performance. Fourth, the suspension system assists in achieving low or zero track and camber change during vertical wheel travel resulting in low tyre wear. Fifth, when conveniently used in four wheel vehicles, required suspension characteristics as well as steering stability and steering geometry can be achieved.

The vehicle suspension system of the present invention may be more fully understood from the following non-limiting description of a preferred embodiment thereof made with reference to the accompanying drawings in which:

Figure 1 is a front isometric view of a suspension system for a steered vehicle in accordance with a first embodiment of the present invention.

Figure 2 is a plan view of the suspension system shown in Fig. 1.

Figure 3 is a detail isometric view of a suspension system showing assembly of the wheel, stub axle, arms and vertical links of a suspension means within the suspension system of Fig 1.

Figure 4 is a schematic representation of a suspension means within the suspension system of Fig 1.

Figure 5 is a schematic representation of the suspension system shown in Fig. 1 and including both suspension means as schematically illustrated in Fig. 4.

Figure 6 is a second front isometric view of a suspension system excluding steering arrangement (for ease of illustration) for a vehicle in accordance with a first embodiment of the present invention.

Figure 7 provides schematic views of a suspension means of the invention, as shown in Figs. 1 to 6, illustrating toe and camber change parameters and steering axis (Fig. 7c).

Figure 8 is a front isometric view of a suspension system in accordance with a second embodiment of the invention.

Figure 9 is a front isometric view of a suspension system in accordance with a third embodiment of the invention.

Figure 10 is a plan view of a suspension system, similar to that of the first embodiment, and incorporating a different steering system.

Figure 11 is a front isometric view of a suspension system in accordance with a fourth embodiment of the invention.
Figures 1 to 6 and 8 to 10 show a suspension system 10 for a steered four wheel automotive vehicle, operation of the steering system 60 being controlled by driver operation of steering wheel 68 (as shown in Figs. 2 and 5). The automotive vehicle has two front wheels 40 mounted on stub axles 16, each wheel 40 being steerable. Each of the front wheels 40 are provided with individual suspension means 15, forming part of suspension system 10, to absorb shocks caused by passing over bumps and other minor obstacles and faults, such as potholes, in a road. The suspension means 15 are mounted outboard of each of the vehicle wheels 40. That is, each suspension means 15 is located closer to the periphery of the vehicle than its respective wheel 40. Each wheel 40 is provided with independent suspension by each suspension means 15.

The suspension system 10, which comprises the suspension means 15, is of twin arm type. Therefore, each suspension means 15 of the suspension system 10 comprises a pair of arms or links 11, 12 extending along the longitudinal plane of a vehicle outboard of the wheel 40. These longitudinally extending arms 11, 12, forming essential components of a twin arm suspension system, are disposed one above the other with the top arm 11 of each pair being the upper arm 11. The other arm is the lower arm 12. Rear ends of the upper and lower arms 11, 12 are pivotably connected to the chassis (not shown) of the vehicle at pivot joints 111 and 112.

The upper and lower arms 11, 12 of each suspension means 15 are connected through vertical links 14 through ball joints 27 to form the basic structure of the suspension system 10.

The suspension system 10 provides suspension for steered wheels 40 of the vehicle.

Therefore, the vertical links 14 of suspension system 10 are connected, through a linkage arrangement including ball joints 25 to a steering system 60 comprising steering wheel 68, steering column 62 and other components for the steering system which include links in the form of divergent tie rods 23, one tie rod 23 corresponding to each wheel 40. Each steering link or tie rod 23 is pivotally connected, at one end, to a steering mechanism 65 here illustrated of conventional rack and pinion type. Rack and pinion mechanism 65 is an elongate structure which extends horizontally above wheel 40 height. Rack and pinion mechanism 65 has opposed ends, each end being located outboard of each wheel 40.

However, other steering systems may be used as generically illustrated by the schematic steering mechanism block 165 in Fig. 10. For example, the steering mechanism could include a half rack with bellcrank, a recirculating ball-screw with bellcrank and so on).
At the other end, each steering tie rod 23 is connected to a vertical link 14 through ball joint 25 to a steering arm 24 each located above wheel 40 height. Each steering tie rod 23 and steering arm 24 overlaps its respective wheel 40.

Suchlinkage arrangement ensures that steering wheel 68 rotation, during steering results in steering of vehicle wheels 40. A steering axis for each wheel 40 is defined by vertical links 14, as visualized through a line joining ball joints 27 of each vertical link 14 to upper arm 11 and lower arm 12. This steering axis is shown schematically as 610 in Fig. 7(c). The steering axis passes through vertical link 14, tie rod 23,steering mechanism block 165 and steering column 62.Steering axis 610 extends in an upward and rearward direction with respect to the longitudinal vertical plane of the vehicle, as above described, giving the vehicle including the steering system its required geometry and stability.
The connection of upper and lower arms 11, 12 of the suspension system 10 to the vertical links 14 through ball joints 27 is shown conveniently in Figs. 3 and 8.

Each arm 11, 12 of each suspension means 15 of the suspension system 10 is independently connected by pivot joints to the vehicle body frame or chassis. Each arm 11, 12 is then allowed to pivot about a pivot axis 111A and 112A of each joint 111, 112. For the illustrated suspension system 10, the pivot joints 111, 112 are designed to achieve zero camber and change during vertical wheel travel when driving. Camber and toe change are selected in the design phase and a zero camber change during vertical wheel 40 travel (as opposed to static condition) were selected for the suspension system 10 being described. To that end, each of the joints 111 for the upper arms 11 have coaxial pivot axes or a common pivot axis 111A. Each of the pivot joints 112 for the lower arms 12 also have coaxial pivot axes or a common pivot axis 112A. These pivot axes 111A and 112A are horizontal. However, for a zero camber change design as here described, the pivot axis of each joint 111, 112 is transverse being set parallel to a transverse axis B of the vehicle; that is an axis perpendicular to the longitudinal axis A of the vehicle. Fig. 7 demonstrates the parameters i.e. angle B and O of the pivot axes 111A and 112A with respect to transverse axis B which need to be selected along with other appropriate lay out parameters like steering system hardpoints to achieve desired camber and toe variation. For a zero camber change, each parameter B and has a value of zero.

However, the suspension system 10 could be designed to have different camber and toe angle change. Fig.' 7 illustrates some design possibilities.

Forexample, upper arm 11 pivot axis 111A may be inclined, at various angles with respect to the transverse axis B. Alternatively, the lower arm 12 pivot axis 112A can be inclined with respect to transverse axis B. It is also possible to incline both pivot axes 111A and 112A to the transverse axis B in order to achieve a desired camber and toe change.

Each wheel 40 is rotatably mounted on a stub axle 16. Stub axles 16 for the wheels 40 are connected to front terminal ends 12a of the lower arms 12 of each suspension means 15 of the suspension system 10, inboard of the vertical links 14 connecting the lower and upper arms 11, 12 of the suspension system 10. Each of stub axles 16 are integrated with, or form part of, the vertical links 14 connecting the lower and upper arms 11, 12 of each suspension means 15 of the suspension system 10.

The upper and lower arms 11, 12 of the suspension system 10 have different geometry.

The upper arms 11 are wedge shaped, and approximately triangular in shape. The lower arms 12 are in the form of angled members tending to angle or curve - in a forward direction - toward the centre longitudinal axis A of the vehicle. The dimensions of each of the upper and lower arms 11, 12, particularly in longitudinal direction, are chosen based on packaging requirements and locations of upper and lower arm 11, 12 mounting pivot joints 111, 112 selected such that the suspension system 10 provides desired suspension characteristics. The dimensions, particularly longitudinal dimensions of the upper and lower arms 11, 12 may be selected to achieve desired caster and trail change.

The lower arms 12 of the suspension system 10 may optionally be connected by a cylindrical spring steel bar 17 which is a vehicle stabiliser acting as an anti-roll device preventing relative rotation of one suspension means 15 relative to the other suspension means 15. If this bar 17 is fixed to chassis frame and rotation locked, the torsion bar 17 supplements the shock absorption provided by the coil springs 21 . which act as shock absorbers for each suspension means 15 of the suspension system 10, as illustrated in Fig. 8. It may be noted that the coil springs 21 are mounted outboard of wheels 40. The coil springs 21 are designed in accordance with conventional shock absorber design practice. Coil springs 21 may have

adjustable spring stiffness, adjusters 21a being provided for this purpose. Coil springs 21 are disposed above upper portions of dampers 35, of hydraulic cylinder type, which provide necessary damping for improved rideability. Coil springs 21 may comprise multiple springs of different spring stiffness. Dampers 35 are mounted to lower arms 12 by spherical joints 37 incorporating bushes with limited conical
flexibility. Dampers 35 are not shown in Fig. 3 for ease of illustration.

In an alternative embodiment illustrated in Fig. 8, when torsion bar 17 is locked to the chassis of the vehicle through mounting member 46, the torsion bar 17 may provide sufficient spring action to act as a torsion spring eliminating need for coil springs 21 which were provided in the suspension systems shown in Figs. 1 to 5. Dampers 35 remain in the suspension system 10. The torsion bar 17 may be mounted along the pivot axis of the lower arms 12 of the suspension system 10. However, torsion bar 17 could be mounted at other points of the lower arms 12. In such case, additional links would be.necessary. Alternatively the torsion bar spring can also be mounted along the pivot axis of the upper arm 11.

An anti-roll bar 170 may be mounted between the upper arms 11 of the suspension system 10. This possibility is illustrated in Fig. 9. Here, as seen with further reference to Fig. 5, the anti-roll bar 170 is mounted along the common horizontal pivot axis 111A of the upper arms 11 of the suspension system 10. Fig. 5 also shows the narrow track nature of the vehicle given the small separation distance, or narrow track, C, between each of the front wheels 40. In an alternative construction, shown in Fig. 11, the anti-roll bar 170 is mounted between upper arms 11 of the suspension system 10 through hinged links 175, one hinged link 175 being provided for each upper arm 11. Anti-roll bar 170 may be connected to hinged links

175 by pivot joints 173. This resists relative rotation of each suspension means 15
relative to the other suspension means 15. An anti-roll bar could also be mounted to
lower arms 12 of the suspension system 10, through hinged linkages, to resist such
relative rotation of each suspension means 15 relative to the other suspension
means 15.

Although the suspension system 10 has been described with reference to the front suspension for a vehicle, it may be understood that the same suspension

system - having the same components - may be used for rear and intermediate wheel suspension also.

The above described vehicle suspension system 10 has a number of advantages over conventional lateral mounted suspension systems. First, the suspension system 10 should enable significant weight reduction in body/frame structure. Second, mounting the suspension system 10 outboard of the vehicle wheel(s) enhances sprung mass roll stiffness with respect to un-sprung mass. Third, the suspension system 10 assists to provide better anti-dive performance as a major component of braking load is transferred through the links resulting in limited or no suspension compression under braking.

Fourth, the design for no track and camber change results in low tyre wear. Fifth, when conveniently used in four wheel vehicles, required suspension characteristics as well as steering stability and steering geometry, achieved through steering axis 610, can be achieved. When a steering mechanism is disposed to "overlap" wheels 40, a simple steering mechanism, for example as above described may be employed.

Modifications and variations to the vehicle suspension system of the present invention may be apparent to the skilled reader of this disclosure. Such modifications and variations are to be deemed within the scope of the present invention.

WE CLAIM:

1. A suspension system for a vehicle having a chassis and comprising:
a pair of wheels, each wheel of said pair of wheels being rotatably mounted to an axle connected to the vehicle chassis and steerable by a steering system comprising a steering mechanism connected to each said wheel; and
a suspension means of double arm type extending longitudinally for each wheel of said pair of wheels wherein each suspension means comprises vertically disposed upper and lower arms extending parallel to a longitudinal axis or plane of the vehicle, said upper and lower arms being pivotally connected by a vertical link to form a suspension assembly located outboard of each wheel and wheel track for the vehicle and wherein said vertical link is operatively connected to said steering mechanism by a linkage arrangement overlapping said wheel and said vertical link defines a steering axis located outboard of each said wheel.

2. A system of claim 1 wherein said steering mechanism extends horizontally in a direction between each wheel of said pair of wheels at above wheel height.

3. A system of claim 2 wherein said linkage arrangement includes steering tie rods which overlap each wheel of said pair of wheels.

4. A system of any one of the preceding claims wherein said steering mechanism is selected from the group consisting of a rack and pinion system, a half rack and bellcrank system and a recirculating ball screw with bellcrank system.

5. A system of claim 4 wherein said steering mechanism is a rack and pinion system.

6. A system of any one of the preceding claims wherein said steering mechanism is pivotally connected to each said vertical link through a tie rod, said tie rod overlapping each wheel to connect to the steering arm on said vertical link, said steering arm being located above wheel height.

7. A system of any one of the preceding claims wherein a steering axis of said steering system is inclined to a longitudinal vertical plane of said vehicle and extends upward in rearward and outward direction with respect to said longitudinal vertical plane of said vehicle.

8. A system of any one of the preceding claims wherein each arm of the suspension system is independently connected by pivot joints to the vehicle chassis such that each arm is allowed to pivot about a pivot axis of a pivot joint forming an independent suspension, the orientation of said pivot axis defining wheel camber, roll centre height and toe change during wheel vertical travel.

9. .A system of claim 8 wherein, for a desired roll centre height of said vehicle, a pivot axis of said lower arm is inclined inwardly, frontward and upward with respect to a transverse axis of the vehicle and said pivot axis of said upper arm is inclined inwardly, rearward and downward with respect to said transverse axis of said vehicle.

10. A system of claim 7, 8 or 9 wherein, for zero camber change, the pivot axis of each joint for an arm of a suspension assembly is set substantially parallel to the pivot axis of each corresponding joint for the other arm of the suspension assembly and also to a transverse axis of the vehicle, said transverse axis being perpendicular to said longitudinal plane of said vehicle.

11. A system of any one of the preceding claims wherein suspension means are provided for each of a pair of wheels, each wheel being located on an opposed side of said longitudinal axis of said vehicle and pivot axes for pivot joints for said arms of each suspension assembly are coaxial and horizontal.

12. A system of any one of the preceding claims wherein each wheel is mounted on a stub axle extending inboard of the vehicle.

13. A system of claim 12 wherein said stub axle is integrated with a vertical link connecting the lower and upper arms of the suspension system.

14. A system of any one of the preceding claims wherein said suspension means for a wheel comprises a shock absorption system including damping members located outboard of said wheel.

15. A system of any one of the preceding claims wherein a first suspension means is provided for one wheel of a pair of wheels and a second suspension means is provided for a second wheel of said pair of wheels, each wheel of said pair of wheels being located on an opposed side of said longitudinal axis of said vehicle and a bar or tube connects a longitudinally extending arm of said first suspension means with a corresponding longitudinal extending arm of said second suspension means to resist relative rotation of the suspension means with respect to each other.

16. A system of claim 15 wherein said bar or tube connects longitudinally extending upper arms of each suspension means to resist relative rotation of each suspension means with respect to each other.

17. A system of claim 15 or 16 wherein said bar or tube connects longitudinally extending lower arms of each suspension means to resist relative rotation of each suspension means with respect to each other.

18. A system of any one of claims 15 to 17 wherein said bar or tube is pivotably mounted on a vehicle body frame or said vehicle chassis and connected, through hinged links, to longitudinally extending upper arms of each suspension means to resist relative rotation of each suspension means with respect to each other.

19. A system of any one of claims 15 to 18 wherein said bar or tube is pivotably mounted on a vehicle body frame or said vehicle chassis and connected, through hinged links, to longitudinally extending lower arms of each suspension means to resist relative rotation of each suspension means with respect to each other.

20. A system of any one of claims 15 to 19 wherein said bar or tube is a torsion bar spring fixed to a vehicle body frame or said vehicle chassis to resist relative rotation of each suspension means with respect to said vehicle body frame or vehicle chassis.

21. A system of any one of the preceding claims wherein each upper arm of a suspension means is wedge shaped and each lower arm is of arcuate shape.

22. A vehicle comprising a suspension system as claimed in any one of the preceding claims.

23. A vehicle of claim 22 being a four wheel vehicle.