GB2300840A

GB2300840A - Vehicle suspension system

Info

Publication number: GB2300840A
Application number: GB9510089A
Authority: GB
Inventors: Louis Karmios
Original assignee: Individual
Current assignee: Individual
Priority date: 1995-05-18
Filing date: 1995-05-18
Publication date: 1996-11-20
Anticipated expiration: 2015-05-18
Also published as: GB2327650A; GB9824557D0; GB2327650B; GB2300840B; GB9510089D0

Abstract

A rocker unit for a vehicle suspension system comprises a first site 9 for pivotable connection to an upper suspension element 1, a second site to receive a lower suspension element 2, the first and second sites being spaced apart from one another, and a third site 11 for pivotal connection to a suspension element comprising or connected to a damping unit 7 of a suspension system, the third site 11 being spaced apart from the first and second sites and located below the second site, a portion of the rocker unit between the second and third sites defining a moment arm such that a force or a component of a force acting on the third site creates a moment about the second site. The suspension elements may be wishbones, and the damper connected as shown, or alternatively inboard on chassis 3 (Fig 4, not shown). The upper wishbones on either side may be connected by a damper whose movement is subject to a torsion member (Fig 6, not shown). Constructions of dampers are described (Figs 7 and 8, not shown).

Description

"Improvements in or relating to vehicle suspension systems" THIS INVENTION relates to improvements in or relating to vehicle suspension systems and, in particular, improvements in or relating to so-called "double wishbone" suspension systems.

One favoured suspension system is the so-called "double wishbone" suspension which involves the use of a pair of wishbones, an upper wish-bone and a lower wishbone, which extend from a vehicle's chassis. Both wishbones are pivotally mounted on the vehicle chassis to allow free movement of the wishbones in the vertical plane. The other ends of the wishbones are joined by a stub axle or upright to which a wheel is attached. A pushrod is connected to the lower of the two wishbones at a position adjacent the upright or stub axle. The pushrod carries the weight of the vehicle to a spring and damping system which may be located either inboard of the vehicle on the chassis or between the pushrod and the chassis, i.e. outboard of the vehicle chassis.

The upright is pivotally mounted on the wishbones to allow both the wheel to turn with respect to the wishbones to provide a steering movement and to allow a rotational displacement of the wheel with respect to the chassis in the vertical plane. A steering rod is connected to the upright to effect steering of the wheel.

As the vehicle takes a corner, as well as preventing the wheels from leaving the ground during, for example, a jolt or a bump, the suspension system must absorb the additional cornering forces experienced by the vehicle during cornering. This cornering force (lateral force) results in the wheel undergoing a certain amount of sideways displacement as the spring system is compressed as well as an angular displacement of the vertical plane of the wheel with respect to the chassis, which displacement is herein termed cambering. A wheel is negatively cambered when the top portion of the wheel is tilted toward the chassis. Positive camber comprises tilting the top of the wheel away from the chassis.

The wheel surface in contact with the road surface acts as a fulcrum for the lateral force being exerted through the wishbones onto the wheel by the vehicle chassis (shown schematically in Figure 1 of the accompanying drawings). The lateral force is transmitted along the wishbones and causes the wheel to adopt a positive camber so that, during cornering, the wheel does not remain flat on the road surface thereby reducing the grip of the wheel on the road surface. This is clearly disadvantageous. To remedy this problem, known designs build in a certain amount of negative camber into the wheels so that when the additional cornering forces are applied and the wheels rotate with respect to the chassis, the wheels adopt a substantially vertical orientation. However, this built-in negative camber is disadvantageous in every other respect, particularly during braking and acceleration.

The present invention seeks to solve the above mentioned problems and, in one aspect, the present invention provides a rocker unit for a vehicle suspension system comprising a first site for pivotal connection to an upper suspension element, a second site to receive a lower suspension element, the first and second sites being spaced apart from one another, and a third site for pivotal connection to a suspension element comprising or connected to a damping unit of a suspension system, the third site being spaced apart from the first and second sites and located below the second site, a portion of the rocker unit between the second and third sites defining a moment arm such that a force or a component of a force acting on the third site creates a moment about the second site.

Whilst it is known to mount damping units of a vehicle suspension in a transverse orientation, such transverse damping units normally comprise a conventional type of damper employing a piston moving in an oil-filled cylinder. It is also known to use a transverse damping unit employing a gas-pressurised damper of conventional construction in which the oil in the cylinder is pressurised by a gas chamber located at one end of the cylinder or at a location remote from the cylinder. These conventional dampers are not, however, really adapted for transverse mounting.

Accordingly, in a further aspect of the present invention there is provided a transverse damper for damping loads applied to either end thereof comprising: a cylinder filled with hydraulic fluid; two pistons each connected to a respective piston rod, one piston being housed in one end of the cylinder and the other piston being housed in the other end of the cylinder such that the pistons are moveable along the cylinder when loaded; a resilient member provided on each of the piston rods to engage with and resist movement of the respective piston into the cylinder; and a passage in fluid connection with the cylinder and an hydraulic fluid reservoir, which passage is closeable by a valve unit.

To vary the roll stiffness of a vehicle, i.e. the roll resistance provided between the suspension system and the vehicle chassis, it is necessary to change the antiroll bar fitted to the vehicle. This is clearly disadvantageous and requires pitstops for racing vehicles or off-road maintenance for road vehicles to effect the changes to achieve the required balance between the front and rear end suspension systems. Since the roll resistance is a function of many parameters which change with the condition of the vehicle and the driving conditions, the roll resistance varies continuously and frequent changes of the anti-roll bar would be necessary to accommodate the varying roll resistance in order to maintain the desired balance between the front and rear end suspension systems.

Accordingly, another aspect of the present invention provides a lateral load balancing system for a vehicle comprising: means for engagement with a damping unit moveable with respect to the vehicle in a first direction; a lever arm of predetermined length extending in a second direction substantially normal to the first direction from the damping unit engagement means; and a torsion element connected to the lever arm and mounted on the vehicle for torsional displacement by the lever arm, the torsion element extending in a third direction substantially normal to the first and second directions such that movement of the damping unit to and fro in the first direction is transferred to and exerts a torque on the torsion element to resist the movement of the damping unit to or fro in the first direction.

A conventional single damper is not suitable for use in conjunction with a lateral load balancing system embodying the present invention, since such a conventional damper is normally in a biased condition. Thus, although the same pressure exists on either side of the piston head, the forces that act upon either side of the piston head are different because the respective surface areas of the sides of the piston head are different due to the piston rod extending from only one of the surfaces of the piston head.

This causes the piston to be pushed out of the cylinder, thereby exerting a bias loading on the chassis.

To alleviate this problem, another aspect of the present invention provides a non-biassed damping unit comprising: a cylinder filled with an hydraulic fluid having two open ends; a piston rod extending through one open end and out of the other open end of the cylinder and being sealed thereto; and a piston fixed to the piston rod and moveable with respect to the cylinder along the direction of travel of the piston rod, the piston dividing the cylinder into two chambers, one on either side of the piston, the surface area of the piston presented to the one chamber being equal to the surface area of the piston presented to the other chamber.

In order that the invention may be more readily understood, embodiments thereof will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a schematic front view showing a wheel, a known double wishbone suspension system, and a vehicle chassis; Figure 2 is a front view of a rocker unit embodying one aspect of the present invention fitted to a wheel mounted on a chassis by a double wishbone suspension system including an outboard spring/shock absorber unit, the suspension system and the chassis being shown schematically; Figure 3 is a perspective view of the rocker unit shown in Figure 2;; Figure 4 is a front view of part of the front suspension of a vehicle incorporating rocker units embodying the present invention, the double wishbone suspension system being shown schematically, together with an inboard transverse spring/shock absorber unit; Figure 5 is a schematic top plan view which diagrammatically illustrates the manner in which he upper front wishbones of the suspension system of Figure 4 are connected to the chassis; Figure 6 is a schematic diagram showing a lateral load balancing system embodying another aspect of the invention, which connects a spring/shock absorber unit of a vehicle suspension system to a vehicle chassis; Figure 7 is a cross sectional view through a spring/shock absorber unit embodying a further aspect of the present invention; and Figure 8 is a cross sectional view through a nonbiassed damper embodying yet another aspect of the present invention.

As shown in Figure 2, one form of vehicle suspension system embodying the present invention comprises a pair of wishbones, an upper wishbone 1 and a lower wishbone 2, which extend outwardly from a chassis 3 of the vehicle. The wishbones 1, 2 are pivotally mounted at either end to, respectively, the chassis 3 and a rocker unit 4. The rocker unit 4 connects the two wishbones 1, 2 and a cantilevered stub 5 which projects from the rocker unit 4 downwardly of the lower wishbone 2, is connected at its lower end to one end of a pushrod 6 having its other end connected to the chassis 3. The pushrod 6 is fitted with a spring/shock absorber unit 7 in known manner.

Figure 3 shows the rocker unit 4 in more detail.

A substantially C-shaped rocker block 8 is provided at a top end with a first bush 9, the upper wishbone bush, for receiving a pin (not shown) to which the upper wishbone 1 is pivotally attached. At a lower end of the block 8, a further bush, the lower wishbone bush 10, is provided for receiving a pin (not shown) to which the lower wishbone 2 is pivotally attached. The cantilevered stub 5 is formed integrally with the rocker block 8 and projects downwardly from the lower wishbone bush 10 to terminate in a third bush, the pushrod bush 11, for receiving a pin (not shown) to which the pushrod is pivotally connected. A reinforcing strut 12 which is formed integrally with the block 8 extends between the upper wishbone bush 9, and the pushrod bush 11. Thus, three sites are provided on the rocker unit 4 for connection to the suspension system.

The rocker block 8 is also formed with horizontal lugs 13, 14 for pivotally mounting therebetween a bearing carrier 15 for rotation about a vertical axis. A wheel 17 is mounted by the bearing carrier 15 for rotation about a horizontal axis. The bearing carrier 15 allows the wheel 17 to pivot with respect to the rocker block 8 about a vertical axis thereby providing a steering action. A steering rod (not shown) may be fixed to the bearing carrier 15 to effect steering of the wheel.

The wheel 17 may move in the vertical plane upwardly by compressing the spring/shock absorber unit 7 or downwardly by placing the spring/shock absorber unit 7 in tension.

The bottom of a wheel in contact with a road surface acts as a fulcrum, or turning point, for the centrifugal cornering force which would normally cause the wheel to be effectively toppled (positively cambered) by the lateral force being transmitted along the wishbones to the wheel (as shown schematically in Figure 1).

However, an important difference between a suspension system incorporating rocker units 4 embodying the present invention and the conventional wishbone suspension system is that the cantilevered stub 5 of the rocker unit 4 creates a moment arm extending from the lower wishbone bush 10 (the site at which the lower wishbone is connected to the rocker unit) to the pushrod bush 11 (the site of connection between the pushrod 6 and the cantilevered stub 5) such that, during cornering, the centrifugal force imparted by the chassis 3 in addition to the vertical forces acting on the pushrod 6 causes, in the example shown in Figure 2, a clockwise rotational force R about the lower wishbone bush which acts to counteract and overcome the tension force in the upper wishbone.The force R therefore tends to rotate wheel 17 into a negative camber position rather than, as in the known systems the wheel being rotated outwardly to a positive camber position.

By connecting the lower end of the pushrod 6 to the pushrod bush 11 at the free end of the cantilevered stub 5 below the lower wishbone bush 10, a lever arm is defined which generates a clockwise moment about the pivot point of the lower wishbone bush 10 to counteract at least some of the tension force being transmitted from the chassis 3 along the upper wishbone 1. This reduces and, in some circumstances, even overcomes, the tension force transmitted down the upper wishbone 1 from the chassis 3 when cornering.Thus, when using a rocker unit 4 embodying the present invention, and depending upon the length of the moment arm and the stiffness of the spring/shock absorber unit 7, the wheel 17 will either be rotated into a less positive camber position during cornering, not rotated at all so that the wheel is substantially vertical and flat on the road surface during cornering, or, preferably, rotated into a slightly negative camber position during cornering.

Figure 4 shows the rocker unit 4 of Figures 2 and 3 used in a different form of suspension system to that shown in Figure 2. Rather than the spring/shock absorber unit 7 being located on the pushrod 6 between the chassis 3 and the rocker unit 4, the spring/shock absorber unit 7 of the suspension system shown in Figure 4 is located inboard of the chassis 3. For the purposes of this portion of the description the spring/shock absorber unit 7 may be regarded as being fixed to the chassis 3, although the particular manner in which the spring/shock absorber unit is fixed to the chassis will be discussed later. By locating the spring/shock absorber unit inboard on the chassis, the aerodynamics of the suspension system are improved since the clutter of the spring/shock absorber unit is located in the nose cone or body of the vehicle rather than being in an exposed position.

As shown in Figure 4, the pushrod 6, which is angled upwardly from the rocker unit 4, is connected to the spring/shock absorber unit 7 by way of a lever-cam 18, the spring/shock absorber unit being located horizontally on the chassis in a transverse orientation.

In the system shown in Figure 4, the upper wishbone 1 comprises, as illustrated in Figure 5, a rear arm 1A which is pivotally connected to the chassis 3 and a front arm 1B which extends from the upper wishbone bush 9 of the rocker unit on one wheel, through the chassis, via a pivotal linkage 1C, to the upper wishbone bush 9 of the rocker unit of the opposite wheel so that any cambering movement of one wheel with respect to the chassis is reflected by a similar cambering movement in the opposite wheel. As shown in Figures 4 and 5, the upper wishbone linkage 1C is guided in this movement by a pair of arms 19, 20 which are pivotally connected to the pivotal lineage 1C and to the chassis 3.

Preferably, the spring/shock absorber unit comprises a gas-pressurised transverse damper 7 for attachment to and location between each of the two pushrods 6 which extend from the rocker units 4 on either side of the chassis 3. The spring/shock absorber unit, as shown in Figure 4 (and in more detail in Figure 7) consists of a centrally located damper unit 21 and two coil springs 22, 23 located on respective sides of the damper unit 21.

The damper unit 21 comprises a main cylinder 24 and a pair of pistons 26 each attached to a piston rod 25 projecting from a respective end of the cylinder 24. The external end of each piston rod 25 is connected to an appropriate link 27 for connection to a respective suspension pushrod 6. Each spring 22, 23 is compressed between a respective fixed abutment 24A on the cylinder 24 and a respective moveable abutment 27A on the link 27.

Each piston 26 is moveable within the cylinder 24 which is oil-filled. The movement is, however, damped by the leakage of oil between the piston 26 and the cylinder 24 or through a specially provided passage (not shown) in the piston 26. The springs 22, 23 on either side of the damper unit 21 also resist movement of the pistons 26 inwardly of the cylinder 24 and facilitate movement of the pistons 26 outwardly of the cylinder 24.

A portion 25 of each piston rod 25 extends through the respective piston head 26. The end surface 28 of the portion 25A of the piston rod 25 is engageable with a respective floating piston 29 located further inside the cylinder 24. Thus, under normal load conditions, the piston rod 25 will not engage the floating piston 29 but, under increasing loads, for example, during braking, the piston rod 25 does engage the floating piston 29, thereby providing a second stage of damping and resistance.

The cylinder 24 is totally filled with oil, an oil reservoir 30 being located externally of the cylinder 24 and connected to the cylinder 24 by a flow passage 31. A valve 32 is provided between the oil reservoir 30 and the damping unit 7 to regulate the flow of oil through the flow passage. The oil pressurised by a pressurised gas reservoir 30A which is also located outside the cylinder 24, thereby enabling the size of the cylinder to be reduced. An additional advantage of this particular system is that, should there be a leak in the gas reservoir 30A, then such a leak would not represent as large a proportion of the total volume of the reservoir as would have been the case if the reservoir were to be located between the respective oil filled reservoirs.

In a preferred embodiment of another aspect of the present invention, the spring/shock absorber unit 7 is located inboard of the vehicle chassis 3 and is connected to the chassis by means of a lateral load balancing system including a torsion tube 32. As shown in the schematic diagram of Figure 6, the torsion tube 32 is disposed vertically with its lower end fixed to the chassis 3 and its upper end fixed to a locating link 3A. The torsion tube 32 is fitted with a lever arm 33 which extends longitudinally of the chassis 3 and which is connected to the spring/shock absorber unit 7 by a connecting link 34.

Thus, when the vehicle experiences cornering forces, the tendency of the spring/shock absorber system 7 to move laterally with respect to the chassis 3 is transferred to and resisted by the torsion tube 32. By adjusting the length of the lever arm 33, it is possible either to soften the roll resistance of the chassis with respect to the suspension system by increasing the length of the lever arm, or to stiffen the roll resistance by decreasing the length of the lever arm. Such adjustment of the length of the lever arm 33 can be made by the driver from the driver's seat of the vehicle by means of an adjustment link 33A running through from the lever arm 33 to the driver's seat. The lever arm 33 is screwthreaded such that rotation of the adjustment link 33A lengthens or shortens the lever arm.It is, therefore, possible for the driver of the vehicle to balance the softness/stiffness of the roll resistances of the vehicle whilst driving by either softening or stiffening the front and rear roll resistances with respect to one another thus saving valuable time and pit stops for racing vehicles in, for example, practice laps. If necessary, this adjustment feature may be disabled once a desired balance position has been achieved so that such adjustment cannot be made during race conditions as such cockpit adjustment might be against race rules.

Another aspect of the present invention provides a damping unit 35 for a shock absorber unit which provides damping for the relative movement of the chassis and the suspension system to overcome the problem of biassed damping. A conventional single damper is normally in a biased condition since, although the same pressure exists on either side of the piston, the forces that act upon either side of the piston are different because the respective surface areas of the sides of the piston head are different because the piston rod extends from only one of the surfaces of the piston. This causes the piston to be pushed out of the cylinder.

The damping unit 35 shown in Figure 8 comprises a non-biassed damping unit embodying the invention.

The damping unit 35 of Figure 8 comprises a cylinder 36 having a closed end 37 and an open end 38. A piston 40 is received in the cylinder 36 and is connected to a piston rod 39 which extends through the open end 38 of the cylinder. The piston rod 39 extends through the piston 40 and projects towards the closed end 37 of the cylinder 36. The piston 40 is fixed to the piston rod 39 and divides the cylinder 36 into two chambers. The cylinder 36 is formed with two ports 41, 42, one communicating with the first chamber adjacent the open end 38 of the cylinder and one communicating with the second chamber adjacent the closed end 37 of the cylinder. The piston 40 is located between the two ports 41, 42.The open end 38 of the cylinder 36 is provided with a first seal 43 to seal the piston rod 39 in the open end of the cylinder and a second seal 44 is provided at the other end of the piston rod to seal the piston rod in that end.

The cylinder 36 is filled with oil and the two ports 41, 42 are in fluid connection with one another through a flow passage (not shown) to allow movement of oil from one chamber of the cylinder to the other. The flow passage is provided with a valve unit (not shown) which is operable to determine the size of the flow passage and thereby restrict the size of the flow passage to provide the requisite damping. Alternatively, or in addition to this method of control, a small passage may be formed in the piston 40 or between the piston and the cylinder 36 to provide a passage for the oil between the two chambers 41.

42. The damping provided by the damping unit of Figure 8 is non-biassed since both sides of the piston 40 have the same surface area - the piston rod 39 running through the piston and out of both chambers 41, 42.

The body of the cylinder 36 is extended at the closed end 37 to allow movement of the piston rod 39 past the second seal 44. The space 45 provided by this extension is vented to atmosphere by a vent port 46 to prevent additional resistance to movement of the piston 40 being caused by the piston rod compressing air or other fluids in the extension space 45.

It should be noted that the piston 40 may be locked in position with respect to the cylinder 36 by fully closing the valve unit in the flow passage between the ports 41, 42 to prevent any flow of oil along the flow passage (provided that no flow passage exists through the piston head or between the piston head and the cylinder).

In addition to the advantage of non-biassed damping, the damping unit 35 is thus also able to serve as a hydraulic lock in the suspension system.

Claims

CLAIMS:

1. A rocker unit for a vehicle suspension system comprising a first site for pivotal connection to an upper suspension element, a second site to receive a lower suspension element, the first and second sites being spaced apart from one another, and a third site for pivotal connection to a suspension element comprising or connected to a damping unit of a suspension system, the third site being spaced apart from the first and second sites and located below the second site, a portion of the rocker unit between the second and third sites defining a moment arm such that a force or a component of a force acting on the third site creates a moment about the second site.

2. A rocker unit according to Claim 1, wherein each of the sites comprises a bush for receiving a pin for connection with the respective suspension element.

3. A rocker unit according to Claim 1 or 2, comprising means for pivotally mounting on the rocker unit a bearing carrier for rotatably supporting a wheel, whereby to provide steering movement of the wheel with respect to the rocker unit.

4. A rocker unit according to Claim 1 to 2, comprising means for rigidly mounting on the rocker unit a bearing carrier for rotatably supporting a wheel.

5. A rocker unit according to any preceding claim which is integrally formed.

6. A rocker unit according to any preceding claim, wherein the first, second and third sites are connected together in an arc sweeping down from the first site, through the second site to the third site.

7. A rocker unit according to any preceding claim, wherein a reinforcing strut is provided between the first and second sites.

8. A rocker unit according to Claim 7, wherein the provision of the reinforcing strut between the first and third sites defines the point about which the moment is created at a position between the first and second sites.

9. A suspension system including a rocker unit according to any preceding claim.

10. A suspension system according to Claim 9, wherein the upper and lower suspension elements are pivotally mounted to the respective first and second sites and the suspension element comprising or connected to the damping unit is pivotally connected to the third site.

11. A suspension system according to Claim 9 or 10, wherein the suspension element comprising or connected to the damping unit is a pushrod.

12. A suspension system according to any one of Claims 9 to Il, wherein two rocker units according to any one of Claims 1 to 8 are provided on opposite sides of a vehicle chassis and upper suspension elements connected to the first sites of rocker units are connected together by a linkage which is laterally moveable with respect to the chassis.

13. A lateral load balancing system for a vehicle comprising: means for engagement with a damping unit moveable with respect to the vehicle in a first direction; a lever arm of predetermined length extending in a second direction substantially normal to the first direction from the damping unit engagement means; and a torsion element connected to the lever arm and mounted on the vehicle for torsional displacement by the lever arm, the torsion element extending in a third direction substantially normal to the first and second directions such that movement of the damping unit to and fro in the first direction is transferred to and exerts a torque on the torsion element to resist the movement of the damping unit to or fro in the first direction.

14. A lateral load balancing system according to Claim 13, wherein the torsion element is a torsion tube.

15. A lateral load balancing system according to Claim 13 or 14, wherein the length of the lever arm is adjustable such that decreasing the length of the lever arm stiffens the resistance to movement of the damping unit to and fro in the first direction and increasing the length of the lever arm softens the resistance to the movement of the damping unit to and fro in the first direction.

16. A lateral load balancing system according to any one of Claims 13 to 15, wherein, in use, the first direction is substantially parallel to the lateral axis of the vehicle chassis, the second direction is substantially parallel to the longitudinal axis of the vehicle chassis and the third direction is substantially vertical.

17. A lateral load balancing system according to Claim 16, wherein the torsion element provides resistance to lateral rolling of a damper unit with respect to the vehicle chassis.

18. A transverse damper for damping loads applied to either end thereof comprising: a cylinder filled with hydraulic fluid; two pistons each connected to a respective piston rod, one piston being housed in one end of the cylinder and the other piston being housed in the other end of the cylinder such that the pistons are moveable along the cylinder when loaded; a resilient member provided on each of the piston rods to engage with and resist movement of the respective piston into the cylinder; and a passage in fluid connection with the cylinder and an hydraulic fluid reservoir, which passage is closeable by a valve unit.

19. A transverse damper according to Claim 18, wherein the resilient members comprise helical springs.

20. A transverse damper according to Claim 18 or 19, wherein the hydraulic fluid reservoir is pressurised by a gas reservoir located externally of the cylinder.

21. A transverse damper according to any one of Claims 18 to 20, wherein a floating piston is provided inside the cylinder to be abutted by a respective piston rod during travel of the piston rod into the cylinder to provide further damping and resistance to said travel.

22. A transverse damper according to Claim 21, wherein a floating piston is provided for each piston rod.

23. A non-biassed damping unit comprising: a cylinder filled with an hydraulic fluid having two open ends; a piston rod extending through one open end and out of the other open end of the cylinder and being sealed thereto; and a piston fixed to the piston rod and moveable with respect to the cylinder along the direction of travel of the piston rod, the piston dividing the cylinder into two chambers, one on either side of the piston, the surface area of the piston presented to the one chamber being equal to the surface area of the piston presented to the other chamber.

24. A non-biassed damping unit according to Claim 23, wherein the cylinder is provided with first and second ports, the first port being located adjacent the first chamber and the second port being located adjacent the second chamber, the ports being linked together by a flow passage which includes a valve for determining the flow of hydraulic fluid through the flow passage.

25. A non-biassed damping unit according to Claim 24, wherein the valve in the flow passage has a closed position in which the damping unit acts as an hydraulic lock.

26. A suspension system including a rocker unit according to any one of Claims 1 to 8 and/or a lateral load balancing system according to any one of Claims 13 to 17 and/or a transverse damper according to any one of Claims 18 to 22 and/or a non-biassed damping unit according to any one of Claims 23 to 25.

27. A rocker unit substantially as hereinbefore described and as shown in Figures 2, 3 and 4.

28. A lateral load balancing system substantially as hereinbefore described with reference to and as shown in Figure 6.

29. A transverse damper substantially as hereinbefore described with reference to and as shown in Figures 4 and 7.

30. A non-biassed damping unit substantially as hereinbefore described with reference to and as shown in Figure 8.

31. Any novel feature or combination of features disclosed herein.