Abstract:
The present invention provides a shock absorber having improved damping. On the base of the shock absorber there is fastened the bottom of a barrel on which rests the counter-acting spring which urges in expansion the piston of the shock absorber. The barrel contains damping fluid and has a piston which is axially movable with lateral seal. The shock absorber also has an external secondary flow dampening device which is connected to the base of the shock absorber via a tube. In the strut base, and the connecting appendage there is a plug adjustment which moves laterally and limits an alternative path of flow for the liquid through the base flow damper and the piston flow damper respectively. By acting on the plug adjustments it is possible to adjust the braking level in expansion of the strut. Each flow damper also is affixed with a shim. The shim on the piston flow damper will flex at an appropriate pressure in the expansion phase, thereby damping the reaction of the strut to expansion. Alternatively the shim at the base flow damper will flex at an appropriate pressure in the compression phase damping the reaction of the strut to compression.

Description:
TECHNICAL FIELD OF THE INVENTION 
     The present invention relates generally to motorcycles and mountain bikes, and more particularly to suspension fork assemblies for use with the same. Specifically, the present invention provides an apparatus and method for an improved shock absorber having increased damping, with this improved shock absorber providing a suspension with greatly improved stability and damping for a much more stable ride over rough terrain. 
     BACKGROUND OF THE INVENTION 
     The present invention has particular application to motorcycles commonly referred to as “dirt bikes” or mountain bike which are typically ridden over rough terrain and/or on steep uphill or downhill slopes. 
     Of particular concern to the “off-road” motorcycle rider is the jolting of the wheels as disturbances in the ground surface, such as rocks, holes, or vertical drops, are encountered. This jolting is transferred to the rider through the wheels, fork, frame, and ultimately the rider&#39;s body. In addition to the potential discomfort to the rider, there is the added concern for safety. That is, the motorcycle becomes difficult to control at the instant of a severe jolt being experienced by the rider through the handles, and frame. 
     To overcome this problem of severe jolting, designers of motorcycles have developed front and rear wheel, shock absorbing suspension systems. These shock absorbing systems include a rigid rod (or inner tube), which is slidable within a rigid sleeve (or outer tube) and a biasing member which can operate pneumatically, hydraulically, elastomerically or with metallic springs, positioned within the rigid sleeve to achieve the “shock-absorbing” action. The biasing member extends the fork rods relative to the sleeves, and as obstacles are encountered by the front or rear wheel, the biasing members of the fork&#39;s rigid sleeves collapse as the slidable rods are compressed in the sleeves, thereby absorbing the severe jolt. Additionally, the sliding rod may have a slight degree of rotatability within the sleeve. 
     Therefore, when an obstacle is encountered directly, the forces are substantially in the same axis as the suspension system, and the slidable rods are typically displaced uniformly. However, during cornering or other maneuvering, the forces are not in the same axis as the suspension such that torsional and lateral stresses are created, and typically one of the rods is compressed or displaced into the corresponding sleeve more so than the opposite rod. Because the slidable rod has a slight degree of rotatability within the sleeve, high stresses are created at the dropout-to-axle connection when lateral and torsional forces are applied to the wheel in contact with the ground, such as in cornering. 
     Also, when brakes are applied in stopping or cornering, the brakes push outward and a large amount of torsion acts on the lower two fork tubes. The resistance to this torsion is mainly provided by the wheel axle and the brake arch. Thus, increased rigidity and strength are highly desired throughout the front fork, especially at the wheel axle, brake arch and/or crown regions. 
     One new design to increase the strength and rigidity at the wheel axle comprises an enlarged wheel hub and axle (the axle being approximately 20 mm in diameter). While uniform compressions relieve stress on the wheel, fork, steering tube, and steering handle, unbalanced compressions, such as from cornering and maneuvering, the stresses on the wheel axle remain high. Therefore, increased rigidity and strength in the wheel axle is highly desirable for off-road motorcycles. Such a novel design in discussed in co-pending application Ser. No. 09/189,448, which is herein incorporated by reference. However, there remains a need to provide a suspension system which will reduce compression forces incurred during ordinary use of the motorcycle. 
     Furthermore, an additional concern for motorcycle riders is the weight of the bicycle or motorcycle. A lighter motorcycle is more desirable because it takes less force to power and maneuver. As such, manufacturers of high-end performance bikes and their components are continuously upgrading them to decrease the overall weight. This has typically been accomplished in at least three ways. One is to use lighter materials such as aluminum alloys and carbon-graphite components. Another is to decrease the overall number of components that comprise the bicycle or motorcycle. Yet another is to decrease the thickness of the components used without sacrificing their strength. 
     An example of such an improvement is described in co-pending application Ser. No. 09/236,998 (the “&#39;998 application”), which is herein incorporated by reference. In this case, separate components are combined at the front fork suspension system of the bicycle. Typically, a front fork suspension system includes a crown which allows attachment of the central steering tube and a pair of parallel fork legs which each comprise an outer rigid sleeve and inner rigid rod which are slidably engaged with each other. Conventionally, the crown is connected to the fork legs via an adhesive or some form of mechanical connection (i.e., screws). In one conventional system, the crown is provided with three openings wherein the outer two openings has slits near each of the outer ends. The center opening receives the steerer tube, usually press fit into this opening. The outer two opening receive the upper ends of the parallel fork legs, usually the upper ends of the inner rigid rods. Then, screw(s) or some other threaded fastening device(s) is employed to close or clamp the crown openings onto the upper ends of the inner rigid rods to form a tightly secured attachment. 
     Although quite simple, this mechanical means for attaching the fork legs to the crown has several disadvantages, some of which include increased overall weight of the forks, increased number of stress points as well as increased stresses at these points, decreased overall strength and stability, etc. The invention of the &#39;998 application has overcome these shortcomings through a novel method of manufacturing the crown and legs as a single component. This “monolithic” crown/fork design results in an overall lighter fork due to the elimination of extra components, increased strength and stability due to the elimination of high stress locations as well as a reduction in the stresses created at the interface of multiple components. 
     Also, in conventional suspension forks, a brake arch is typically mounted on the upper portion of the lower fork legs via screws or other threaded fastening devices, one on each rod, while the brake arch has receptacles for mounting brake calipers. In an alternative design, known as an upside down (or inverted) fork, the outer rigid sleeves and inner rigid rods are reversed. More specifically, the crown is connected to the outer rigid sleeves rather than to the inner rigid rods as previously described. This inverted design provides greater strength and stability at the crown/fork leg interface. 
     Additionally, recent trends show an increased use of disc brakes on motorcycles due to their increased performance and high durability. Typical disc brake systems are mounted on one of the dropouts at the wheel axle for maximum performance. Conventionally, the disc brakes comprise a separately mounted caliper containing the brake pads which, when in the closed position (i.e., pressed together), provide a high degree of frictional force to slow the wheel to a stop. It is therefore appreciated that the present invention can be used with motorcycles having either a conventional brake arch design or a conventional disc brake system. 
     SUMMARY OF THE INVENTION 
     The present invention relates generally to suspension systems for bicycles or motorcycles. In particular, the present invention provides an adjustable shock absorber comprising a second damping mechanism to receive fluid from the main strut(s) to provide an enhanced damping of the shock absorber system in the compression phase. It is therefore an object of this invention to provide an improved shock absorber comprising a secondary damping mechanism (hereafter “SDM”,or fluid chamber) which thereby provides increased damping and stability, without significantly increasing the overall weight of the suspension system. These and other advantages of the present invention will become more thoroughly apparent through the following description of the preferred embodiments and the accompanying drawings. 
     It will be appreciated that those skilled in the art will recognize that variations and modifications may be made without departing from the true spirit and scope of the invention. The invention is therefore not to be limited to the illustrations and descriptions set forth below but is to be determined by the appended claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A further understanding of the present invention can be obtained by reference to a preferred embodiment set forth in the illustrations of the accompanying drawings. Although the illustrated embodiment is merely exemplary of systems for carrying out the present invention, both the organization and method of operation of the invention, in general, together with further objectives and advantages thereof, may be more easily understood by reference to the drawings and the following description. The drawings is not intended to limit the scope of this invention, which is set forth with particularity in the claims as appended or as subsequently amended, but merely to clarify and exemplify the invention. 
     For a more complete understanding of the present invention, reference is now made to the following drawings in which: 
     FIG. 1 shows an overall front plan view of a preferred embodiment of the apparatus for providing improved damping in a suspension system according to the present invention; 
     FIG. 1 a  shows an overall front plan view of a preferred embodiment of the apparatus for providing improved damping in a suspension system according to the present invention in the expansion phase; 
     FIG. 1 b  shows an overall front plan view of a preferred embodiment of the apparatus for providing improved damping in a suspension system according to the present invention in the compression phase; 
     FIG. 2 shows an enlarged front plan view of the region of the apparatus for providing improved damping in a suspension system shown in FIG. 1 above line A—A; 
     FIG. 3 shows an enlarged front plan view of the region of the apparatus for providing improved damping in a suspension system shown in FIG. 1 below line A—A; 
     FIG. 4 shows an enlarged front plan view of the secondary damping means shown in FIG. 1; and 
     FIG. 5 shows a front plan view of an alternate embodiment of the apparatus for providing improved damping in a suspension system according to the invention without the use of the external damping means. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As required, a detailed illustrative embodiment of the present invention is disclosed herein. However, techniques, systems and operating structures in accordance with the present invention may be embodied in a wide variety of forms and modes, some of which may be quite different from those in the disclosed embodiment. Consequently, the specific structural and functional details disclosed herein are merely representative, yet in that regard, they are deemed to afford the best embodiment for purposes of disclosure and to provide a basis for the claims herein which define the scope of the present invention. 
     The following presents a detailed description of a preferred embodiment of the present invention. As discussed above, the present invention relates generally to motorcycles, but may be applied wherever suspension systems are used. Specifically, the present invention provides an apparatus and method for improved damping in suspension systems. Reference is herein made to the figures, wherein the numerals representing particular parts are consistently used throughout the figures and accompanying discussion. 
     With reference first to FIGS. 1,  1   a  &amp;  1   b,  shown is an overall front plan view of a preferred embodiment of the apparatus for providing improved damping in a suspension system according to the present invention, including strut  1  and secondary damping means  10 . As depicted, FIGS. 1,  1   a  &amp;  1   b  show secondary damping means  10  attached to strut  1  via tube  3 . During the compression phase of strut  1 , fluid from the internal cavities of strut  1  flows through tube  3  into secondary damping means  10 . Conversely, during the expansion phase of strut  1 , fluid from secondary damping means  10  flows through tube  3  into the internal cavities of strut  1 . Accordingly, secondary damping means  10  provides added damping to existing damping mechanisms within strut  1 , which are described in detail below. 
     The strut  1  of the shock absorber is equipped in the lower part with a connecting appendage  101  (i.e., for the formation of a stem of a fork for a motorcycle, for the fastening to the axis of the rear wheel of the motorbike, etc.). Optionally, strut  1  may be equipped with additional appendages (not shown) for the support of a disc brake caliper or other conventional bicycle or motorcycle component. Similarly, the upper part of strut  1  (See FIG. 2) comprises connecting appendage  102  for attaching strut  1  on its upper end to the motorcycle frame below the seat area. Directly below the connecting appendage  102  is attached a truing cap  16 . The truing cap  16  supports the upper end of the helical coil spring  4  which provides the mechanical damping of the strut. In addition at the center of the connecting appendage  102  is attached the piston  5 . At the center of the piston is a shaft  6  integral with barrel  14 . Within the connecting appendage  102  at the location were the same meets the piston  5  there is a “silo” shaped free space  44 ′. Free space  44 ′ is intersected by a hole  35 ′ that extends from the wall of connecting appendage  102  to the lower edge of the free space  44 ′. Within the hole  35 ′ is a manual shaft adjustment  36 ′ which moves laterally. There is a counterbore  72 ′ about the side of the shaft adjustment  36 ′. Perpendicular to the hole  35 ′, from the bottom of connecting appendage  102  there is a channel  40 ′ which is internally threaded at the base. A spring loaded pin  39 ′, which is externally threaded, is screwed into channel  40 ′. With the shaft adjustment  36 ′ in place, the spring loaded pin  39 ′ limits the movement of the shaft adjustment  36 ′ to the length of the counterbore  72 ′. The free space  44 ′ is at the center of base  20 , and has a silo shaped recess  71 ′ opposite of the shaft adjustment  36 ′, which is designed to accommodate the shaft adjustment  36 ′ at full extension. The movement of the shaft  6  is limited by the shaft adjustment  36 ′. Due to the taper  73 ′ in the shaft adjustment  36 ′, when the shaft adjustment is moved inward the shaft  6  is forced downward. The shaft  6  then restricts flow through the center hole  105 , of the piston flow damper  12  and may even stop flow entirely. 
     As seen in FIG. 3 the strut base  20  is tapered in three levels being most narrow towards the bottom where the connecting appendage  101  is located and widest at the upper most portion where it accepts the strut barrel  14 . Immediately above the connecting appendage  101  base  20  has a cylindrically shaped free space  44  at its center. Free space  44  is intersected by a hole  35  that extends form the wall of base  20  to the lower end of the free space  44 . Within the hole  35  is a manual plug adjustment  36  which moves laterally. There is a counterbore  71  about the side of the plug adjustment  36 . Perpendicular to the hole  35 , from the bottom of base  20  there is a channel  40  which is internally threaded at the base. A spring loaded pin  39 , which is externally threaded, is screwed into channel  40 . With the plug adjustment  36  in place, the spring loaded pin  39  limits the movement of the plug adjustment  36  to the length of the counterbore  72 . The free space  44  is at the center of base  20 , and has a silo shaped recess  43  opposite of the plug adjustment  36 , which is designed to accommodate the plug adjustment  36  at full extension. Resting upon the plug adjustment  36  is a plug  34 . Due to the taper  73  in the plug adjustment  36 , when the plug adjustment is moved inward the plug  34  is forced upward. When forced upward the plug  34  restricts flow through the center hole  45 , of the flow damper base  25  and may even stop flow entirely. 
     At the upper edge of the free space  44  in base  20  is affixed a flow damper base  74 . The flow damper base  74  supports a shim  28 , and ultimately the lower flow damper  25 . The flow damper  25  is held in place by a clip  23 . A helical coil  24  in compression is located above the lower flow damper  25  and below the clip  23 . The helical coil  24  creates a dampening of the initial compression which may be experienced by the strut. Base  20  has a seat  69  where there is fixed the barrel  14 . At the lower end of the barrel  14  there is at least one hole  30  whereby fluid may pass in both the compression and expansion phases. The lower flow damper  25  forms a tight seal  76  with the inner wall of the barrel  14 . There are also at least three holes  110  above the lower flow damper  25  which allow liquid to flow from the barrel  14  in area B, to the free space below support/rebound ring  21 . At the upper most portion of base  20  where it increases in diameter, a seat  75  is formed between the barrel  14  and the wall of base  20 . A support/rebound ring  21  is placed in the seat  75  and a seal is formed by cylindrical washer  22  at the inner wall of base  20 , as well as washer  22 ′ at the outer wall of the barrel  14 . An annular recess  77  is located on the outer portion of the upper third of the support ring  21 . The annular recess provides a movement area for both base  20  and the support/rebound ring  21  during the use of the strut. A cylindrical washer  19  forms a seal at the top of the annular recess  77  to maintain the strut free of foreign material. Resting on top of the support ring  21  is a truing cap  18 . The truing cap  18  supports the lower end of helical coil  4  which provides mechanical dampening of the strut during compression and expansion. 
     Base  20  has an internally threaded recess  87  where hole  30  of the barrel  14  is aligned. The recess  87  is fitted with a screw  85  which is threaded both internally and externally, separated by a flat washer  86 . A valve assembly  26  which is externally threaded is then attached to the screw  85 , again with a flat washer  84  providing separation between the two parts. The tube  3  is attached to the open end of the valve assembly  26 , and passes over to another valve assembly  46 , at the SDM  10  shown in FIG.  4 . The valve assembly  46  attaches to a screw  48 , with a flat washer  47  between the valve assembly  46  and the screw  48 . The screw  48  which is threaded on both sides is attached to a plug  53  at the top of the SDM  10 . A flat washer  50  is located between the top of the plug  53  and the bottom of the screw  48 . The plug  53  has a hole  50  which is tapered and creates a seat  100 . The hole is used to provide a means for adding or removing fluid or possibly relieving pressure within the SDM  10 . A plug  51  is recessed within the hole  50  forming a seal with cylindrical washer  52  at the seat  100 . There is a seat  95  on the plug  53  where the top of the shell  56  of the SDM  10  attaches. The plug  53  has a vertical recess  67  where a cylindrical washer  54  is located, and forms a seal between the shell  56  and the plug  53 . The SDM shell  56  has a recess  60  where a ring clip  66  is fixed. The ring clip  66  supports a bullnose shaped ring washer  59 , which has an internal diameter slightly smaller than the outer shell  56 . A flexible inner shell  58  with a rigid rim is located within the SDM  10 . The rim of the flexible shell  58  is supported from below by the ring washer  59 , and is held in place from above by a washer  57 . The upper surface of the washer  57  forms a seal with the lower surface of the plug  53 , which is supplemented by a cylindrical washer  55  located within a horizontal recess  68  of the plug  53 . The shell  56  of the SDM  10  has an additional vertical recess  64  near the bottom of the SDM  10 . The recess  64  is fixed with a snap ring  63  which supports the damper base  61  by way of the seat  99 . Damper base  61  forms a seal with the shell  56  with a cylindrical washer  62  within a vertical recess  65 . 
     At the top of the barrel  14 , as shown in FIG. 2 a plug  7  forms a seal both with the outer wall of the piston  5 , and the inner wall of the barrel  14 . A cylindrical washer  8  reinforces the later. At the lower end of the piston  5  is affixed a flow damper base  9 . The flow damper base  9  supports a truing cap  17 , a shim  13  and ultimately the upper flow damper  12 . The flow damper  12  is held in place by a clip  15 . A helical coil  11  in compression is located between the lower flow damper  12  and the truing cap  17 . The helical coil creates a dampening of the initial compression which may be experienced by the strut. The flow damper  12  forms a seal with the inner wall of the barrel  14 . The seal forces fluids to flow past the flow damper  12  when the flow damper moves the length of the barrel  14  as a result of compression or expansion of the strut. 
     When the strut  1  is in the fully compressed position the Secondary Damping Means (Hereafter “SDM”)  10  should be filled with a correct amount of suitable fluid. The piston  5  should then be retracted drawing the appropriate amount of fluid from the SDM through the tube  3 , into the barrel  14 . In the compression phase of the strut  1 , as seen in FIG. 1 b  and  2 , the cylindrical coil spring  4  is contracted and the piston  5  passes downward through the plug  7  of the barrel  14 . Fluid in area B of the barrel  14  may take two alternative paths to reach the area above the flow damper  12 . The liquid may pass into the upper flow damper  12  through opening  79 . Opening  79  is restricted in size by the shim  13 . The flex of this shim  13  during the expansion of the strut, to allow an increased flow rate will be discussed later in this section. The fluid then passes out of the flow damper  12  through hole  78 , into the area of the barrel  14  above the flow damper  12  labeled area A. Alternatively the liquid may pass into the center of the piston  5  through hole  105 , up through piston  5  and out into area A through holes  37  and  38 . As described above, the path through the center of the piston may be limited by the forcing of shaft  6  within piston  5  downward, thereby either restricting flow through hole  105 , or blocking it entirely. The manual shaft adjustment  36 ′ would thereby offer a means for a user to adjust the response of the strut to compression and expansion according to his or her specific needs or preferences. 
     The volume above the upper flow damper  12  in area A at full compression is less than the volume of B at full expansion, therefore either the liquid within the strut must be limited to a volume less than or equivalent to the maximum capacity during full compression, or during compression the fluid which is associated with the difference in the respective volumes must pass to the SDM  10  via tube  3 . An alternative embodiment of the strut which does not employ the SDM is shown in FIG.  5 . The flow paths, and operation described in this embodiment would be identical to that available in the alternative embodiment shown in FIG. 5 except for the use of the SDM. 
     If the SDM is employed however in order for the liquid to pass from area A into the SDM  10  upon compression, the fluid may take two alternative paths. The liquid may enter the lower flow damper  25  through opening  27 . The fluid then exits the flow damper  25  through opening  29  into the free space within the barrel  14  below the lower flow damper  25 . The openings  27  and  29  of the flow damper  25  restricts the rate at which the fluid may flow and, and assuming a fluid of low compressibility is used the rate at which the piston  5  may compress is also decreased. The slower reaction of the strut to the changes in the ground surface which results, creates the improved ride quality which is desired. The size of hole  29  is also limited by the shim  28  attached to the base. The shim  28  is manufactured of an appropriate material such that at a certain force during the compression phase the shim will flex downward thereby increasing the area of hole  29 . This increased area will allow greater flow rates of liquid to be achieved at the same pressures. The shim will not flex during the expansion phase however due to the physical limitations placed on it by the flow damper  25 . Therefore at any fixed force and resultant pressure in expansion, and even flow rate of liquid, and therefore rate of compression of the strut should be expected. The second path which the liquid may take is through the center of the flow damper base  74 . The fluid may enter the flow damper base  74  through hole  45 . The fluid will then pass through openings  80  and  81  into area the free space below the flow damper  25 . The amount of flow which may pass in this way may be limited however by movement of the plug adjustment  36  as noted earlier. When the plug adjustment  36  is moved inward the plug  34  is forced into the hole  45  restricting flow through this path. Alternatively when the plug adjustment  36  is moved outward the plug  34  is allowed to fall opening the hole  45 , and restoring flow through this path. 
     The fluid within the free space which is now under pressure due to the compression of the strut flows to the SDM  10  through the hole  30  in the barrel  14 . The fluid passes out of the free space through hole  30  into the valve assembly  26 . While the valve assembly is in the open position fluid will flow through tube  3  into the valve assembly  46  at the other end of the tube  3 . Again providing that the valve assembly  46  is in the open position, fluid will pass through the plug  53 , and into area C of the flexible shell  58 . As the volume of fluid passing through the tubing  3  increases, the pressure within the flexible shell will increase. The increased pressure will produce a Secondary Dampening Means on the strut. The more compressed the strut becomes the greater the pressure within the SDM  10  will become, and the more force that will be required on the strut to continue the compression. 
     As seen in FIG. 3, during the compression phase, liquid within area B is also forced through hole(s)  46  into the free space below the support/rebound ring  21 . The resultant force associated with the increased pressure in this area forces the support/rebound ring upward increasing the compression of the helical coil  4 . This increased compression creates a rebound affect in the strut. Alternatively in the expansion phase the pressure within area B will decrease. Liquid within the free space way below the support/rebound ring will flow to the lower pressure of area B, allowing the support/rebound ring to drop. 
     In the expansion phase of the strut, as shown in FIG. 1 a,  the piston  5  and the cylindrical coil  4  are expanded. The fluid follows the opposite path which it did in the compression phase. Fluid within the SDM  10  which would be under pressure following the compression phase will travel from the area of high pressure within the SDM  10  to the area of lower pressure which is created within the barrel  14  during the expansion phase. Specifically the fluid will flow from area C of the flexible shell  58 , through the plug  53  into the valve assembly  46 . Provided that the valve assembly  46  is in the open position the fluid will pass via tube  3  into the valve assembly  26  at base  20 . The fluid will flow from the strut base  20  into the barrel  14  through hole  30  into the free space below the lower flow damper  25 . The fluid may take two paths from the free space below the lower flow damper  25  to the area B above the lower flow damper  25 . The fluid may enter the flow damper base  74  through openings  80  and  81 . The fluid will then pass through hole  45  through the center of the flow damper base  74  to area B. The amount of flow which may pass in this way may be limited however by movement of the plug adjustment  36  as noted earlier. When the plug adjustment  36  is moved inward the plug  34  is forced into the hole  45  restricting flow through this path. Alternatively when the plug adjustment  36  is moved outward the plug  34  is allowed to fall opening the hole  45 , and restoring flow through this path. The alternative path for the fluid from the free space below the lower flow damper  25  to area B is through the flow damper  25 . The fluid enters through opening  29  and exits the flow damper  25  through opening  27 . The shim  28  will not operate in the expansion phase as it might in the compression phase because it&#39;s movement is physically restricted by the flow damper  25 . Therefore at any fixed force and resultant pressure in expansion, and even flow rate of liquid, and therefore rate of expansion of the strut should be expected. 
     While the strut  1  is in the expansion phase fluid is also flowing from area A above the upper flow damper  12 , into area B, below the upper flow damper  12 . When the piston  5  retracts the volume of area A becomes smaller increasing the pressure within area A and decreasing the pressure within area B. This pressure gradient forces the fluid from area B into area A by way of one of two paths, directly opposite to the compression phase. Liquid may enter the upper flow damper  12  via hole  78 . The fluid then leaves the flow damper through hole  79  and enters the lower pressure of area B. The size of hole  78  is limited by the shim  13  attached to the base  9 . The shim  13  is manufactured of an appropriate material such that at a certain force the shim will flex downward thereby increasing the area of hole  78 . This increased area will allow greater flow rates of liquid to be achieved at the same pressures. This increased flow rate will allow the strut to expand more rapidly damping even further the force which will be transferred through the strut to the user. 
     While the present invention has been described with reference to one or more preferred embodiments, such embodiments are merely exemplary and are not intended to be limiting or represent an exhaustive enumeration of all aspects of the invention. The scope of the invention, therefore, shall be defined solely by the following claims. Further, it will be apparent to those of skill in the art that numerous changes may be made in such details without departing from the spirit and the principles of the invention. It should be appreciated that the adjustable suspension system of the present invention is capable of being embodied in other forms without departing from its essential characteristics.