Abstract:
A suspension assembly for a front end of a vehicle to provide lateral flex for absorption of lateral forces. The suspension assembly comprises a steering shaft including two ends: an end coupled to an upper triple clamp and another end coupled to a lower triple clamp. A spring unit couples one of the two ends of the steering shaft to the associated triple clamp and absorbs forces that are transferred from a road surface up through a front wheel and the pair of forks retained by the upper and lower triple clamps. A pivot mechanism couples the other triple clamp to the other one of the two ends of the steering shaft and creates a pivoting axis. The suspension assembly permits the front end to pivot about the pivoting axis and causes the spring unit to flex laterally in response to bumps in the road surface.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of U.S. patent application Ser. No. 11/672,040, filed Feb. 6, 2007 now U.S. Pat. No. 7,490,843, and claims the benefit of U.S. Provisional Application Ser. No. 60/765,805, filed Feb. 6, 2006, which is hereby expressly incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present invention relates generally to a front end suspension for vehicles, and more particularly, to a suspension for absorbing lateral forces on a motorcycle. 
     BACKGROUND OF THE INVENTION 
     The extreme performance characteristics of modern day grand prix/racing motorcycles have led manufacturers to develop very stiff front end packages, designed to bear huge loads primarily during heavy braking. During this condition, the rearward force on the front tire&#39;s contact patch presses rearward on the lower portion of the forks at the axle and the inertia of the motorcycle&#39;s mass presses forward on the upper portion of the forks at the triple clamps. The resulting flex in the longitudinal direction (direction of travel of the motorcycle) is minimized by increasing the rigidity of the forks. 
     This increased stiffness of the front forks solves the problem of longitudinal flexing during braking. However, the compromise demanded by a stiffer front end is the appearance of chatter, or vibrations resulting from momentary reductions of traction, particularly during turns. Severe leaning angles typically result from motorcycles negotiating these turns and produce conditions conducive to chatter. When the motorcycle is leaning, the tire&#39;s contact patch shifts from the center to side, but the forces from the road are in the vertical direction. Upon hitting little bumps, the vertical force transfers onto the motorcycle mostly laterally. The inability of stiff forks to flex in the lateral direction causes the bumps and imperfections of the road surface to lift up the vehicle, without any elastic restorative forces of the forks being able to maintain pressure of the tire against the road surface. 
     This problem leads to the vehicle losing contact with the road surface which can result in chatter. Being vibration that resonates from the front tire up to the chassis until dampened, chatter is a nuisance to riders and decreases motorcycle performance. Therefore, it is desirable to maintain longitudinal stiffness in the front end for rigidity under heavy breaking and at the same time, reduce chatter for improved handling of the motorcycle. 
     SUMMARY OF THE INVENTION 
     The present invention provides an apparatus for reducing chatter on front ends of vehicles. This invention isolates two distinct stiffnesses of the front end: the longitudinal stiffness and the lateral stiffness. The desired rigidity of the longitudinal stiffness under heavy breaking is maintained, while the lateral stiffness is reduced to provide better dampening under severe leaning angles, and consequently improve handling. The foregoing and other features of the invention will be more readily understood upon consideration of the following detailed description of the invention taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be understood more fully from the detailed description given below and from the accompanying drawings of embodiments of the invention which, however, should not be taken to limit the invention to the specific embodiments described, but are for explanation and understanding only. 
         FIG. 1  is a perspective view of a motorcycle which includes a suspension assembly according to the present invention. 
         FIG. 2  is a perspective view of a front end of a motorcycle including a suspension assembly. 
         FIG. 3  is a front view of the front end of the motorcycle including a suspension assembly and leaning to the right side, such as when the motorcycle is negotiating a right corner. 
         FIG. 4  is a front view of the front end of the motorcycle of  FIG. 3  encountering a bump and leaning to the right side, such as when the motorcycle is negotiating a right corner. 
         FIG. 5  is a front view of the front end of the motorcycle of  FIG. 3  encountering a bump and leaning to the left side, such as when the motorcycle is negotiating a left corner. 
         FIG. 6  is a front view of the front end of the motorcycle of  FIG. 3  using a spring unit that is more rigid than the spring unit in the suspension assembly of  FIGS. 3-5 . The motorcycle is encountering a bump and leaning to the left side, such as when the motorcycle is negotiating a left corner. 
         FIG. 7  is a perspective view of a suspension assembly, including a pivoting axis A and a steering axis B. 
         FIG. 8  is an exploded view of one embodiment of the suspension assembly. 
         FIG. 9  is an exploded view of an alternate embodiment of the suspension assembly. 
         FIG. 10  is a perspective view of a spring unit for use in one embodiment of the suspension assembly. 
         FIG. 11  is an exaggerated perspective view of the spring unit of  FIG. 10  undergoing flex. 
         FIGS. 12-15  show perspective views of spring units for use in alternate embodiments of the suspension assembly. 
         FIG. 16  is a perspective view of an alternate embodiment of the suspension assembly wherein the pivoting mechanism is located in the upper triple clamp and the spring unit is located in the lower triple clamp. 
         FIG. 17  is a perspective view of another alternative suspension assembly including a spring unit mounted in the upper triple clamp. 
         FIG. 18  is a perspective exploded view of the upper triple clamp, spring unit, and a portion of the steering shaft of the suspension assembly shown in  FIG. 17 . 
         FIG. 19  is a sectional view, at an enlarged scale, of a portion of the assembly shown in  FIG. 17 , taken along line  19 - 19  in  FIG. 17 . 
         FIG. 20  is a sectional view of the spring unit shown in  FIG. 18 , taken along line  20 - 20 . 
         FIG. 21  is a perspective view taken from the lower side of the portion of the upper triple clamp shown in  FIG. 19 , together with the associated spring unit. 
         FIG. 22  is a perspective view similar to a portion of  FIG. 18 , showing an alternative spring unit for use in the suspension assembly shown in  FIGS. 17-19 . 
         FIG. 23  is a sectional view, taken along line  23 - 23  in  FIG. 22 . 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring to  FIG. 1 , a motorcycle according to one embodiment of the present invention is shown at  10 . The motorcycle  10  includes a front end  12 , an engine assembly  13 , and a frame  14  supporting a rear wheel  16  via a rear suspension  18 . The front end includes a suspension assembly  20  coupling a front wheel  22  to the frame and aiding in the absorption of lateral forces in certain conditions, as further described below. 
     Turning to  FIG. 2 , the front end of the motorcycle is shown in more detail with several components removed. The front end  12  typically includes a steering tube which is part of, or coupled to, the frame of the motorcycle, to house a steering shaft  24 . For illustrative purposes, the steering tube and parts of the frame have been removed to show additional detail. 
     The suspension assembly  20  includes the steering shaft  24 , an upper triple clamp  26 , a lower triple clamp  28 , a spring unit  30  and a pivot mechanism  32 . The upper triple clamp and the lower triple clamp are adapted to retain a pair of front forks  34 ,  36  coupled to the front wheel  22  via a front axle  38 . Although the front forks are shown throughout this application as non-telescopic forks, the scope of the invention includes front forks having telescopic tubes, built-in rigidity or flex, dampers within, and fork bottoms for coupling to the front axle. One or more of these features may be included in the front forks. Other features of conventional front forks may also be used with the front forks. 
     The suspension assembly  20  may separate flexional stiffness in the longitudinal direction (direction of travel of the motorcycle) from flexional stiffness in the lateral direction (side-to-side or perpendicular to the longitudinal direction). Flexional stiffness in the longitudinal direction may be referred to as “longitudinal stiffness,” whereas flexional stiffness in the lateral direction may be referred to as “lateral stiffness.” By decoupling the longitudinal stiffness and the lateral stiffness in the front end, chatter may be reduced and handling characteristics may be improved. Detailed mechanics of the suspension assembly is described further below. 
     For simplicity, when the front end  12  is mentioned below, particularly in describing movement, the front end refers to the entire front end of the motorcycle  10  without the steering shaft  24  (which is stationary with respect to the frame). For further illustration and as non-limiting examples,  FIGS. 3-6  are provided to exemplify the movement of the front end fitted with the suspension assembly  20 . These depictions are exemplary only and may be exaggerated to show more detail. 
     Front views of the front end including the suspension assembly are shown in  FIGS. 3-6 . The front end of the motorcycle includes a steering axis  40 , extending coaxially through the steering shaft  24 , and two fork axes  42 ,  44 , extending coaxially through each front fork  34 ,  36 . The steering shaft is adapted to rotate about the steering axis  40  to steer the front end  12 . In general, the steering axis and the two fork axes are substantially parallel during travel of the motorcycle. Referring to  FIG. 3 , the front end is turning right and leaning to the right side, such as when the motorcycle is rounding a right corner. 
     While the motorcycle is negotiating a corner, the motorcycle is typically leaning into the turn. The more the motorcycle leans, the greater (steeper) the lean angle. The lean angle at which the turn is made may vary depending on the turn radius, motorcycle speed, tire characteristics, rider handling, and the balance of centrifugal and gravitational forces. For example, the faster the speed and the smaller the turn radius, the greater the lean angle on the motorcycle. When the front end is at a steep lean angle, dampers that are designed to absorb forces in the vertical direction are ineffective at absorbing forces which are effectively acting in the lateral direction. As a result, the front wheel loses contact with the ground and the inertia of the vehicle is slow to react. The suspension assembly may help solve this problem by decreasing the lateral stiffness (or allowing additional flexibility) of the front end for better absorption of lateral forces and improved cornering ability. 
       FIG. 4  depicts the response of the front end  12  shortly after the motorcycle encounters a bump  8  in the road when rounding a corner. When referring to the bump, the terminology may include any imperfections in the road or debris that may contribute an additional force to the front end. This force is generally directed in the vertical direction, and impacts the front end. This vertical force (effectively lateral force on the leaning motorcycle) may be dampened using the suspension assembly. 
     The suspension assembly absorbs energy through deflection of a spring unit, further discussed below, and separates these forces acting on the front end from the frame to minimize the unsprung weight of the motorcycle. With less inertial weight, the front wheel of the motorcycle can return to the road surface in less time. 
     In response to the bump in  FIG. 4 , the front end may shift laterally or roll slightly to the side with respect to the frame of the motorcycle due to the flexibility allowed by the suspension assembly. As shown in this instance, the front forks move with respect to the steering shaft (which is stationary to the frame) and thus the steering axis and fork axes are no longer substantially parallel. 
     As the front end hits the bump in the road while traveling at an initial lean angle, the spring unit allows for displacement of the front end. For example, in reaction to the bump, the steering shaft remains substantially inclined to the initial lean angle whereas the rest of the front end has shifted to a different lean angle. During this instance, the front end may have a lean angle greater than the initial lean angle.  FIGS. 3 and 4  may be contrasted to see the effect of the road imperfection on the front end and the suspension assembly. 
     Referring to  FIG. 5 , similar to  FIG. 4 , the motorcycle encounters a bump as it leans left into a left corner. The suspension assembly allows the front end to shift laterally to a larger lean angle from an initial lean angle and to the opposite side from that depicted in  FIG. 4 . As shown, the steering shaft remains inclined at the initial lean angle while the fork axes are still parallel to each other, but have shifted to a steeper lean angle. The spring unit  30  absorbs lateral forces, similarly as described above. 
     In contrast to  FIG. 5 ,  FIG. 6  shows the front end fitted with a stiffer spring unit  31  in the suspension assembly. Depending on the rigidity of the spring unit, the lateral movement of the suspension assembly and front end may be very small or not visible when the spring unit is absorbing lateral forces. 
     Referring to  FIG. 7 , one embodiment of the suspension assembly  20  is shown. The upper triple clamp  26  is a shaped plate including retention braces  46  on each side for retaining and securing the front forks  34 ,  36  (not shown). These retention braces may be adjusted to retain front forks with varying diameters. In the middle is an aperture  48  for housing the spring unit  30  and the steering shaft  24 . The upper triple clamp further includes screw holes  50  that align with the spring unit and allow screws (not shown) to fasten to the spring unit by inserting through the bottom or top of the upper triple clamp. Attaching the spring unit to the upper triple clamp is not limited to using screws and screw holes, but may include using other fasteners and methods of coupling those components. 
     The steering shaft  24  is disposed substantially perpendicular to the upper triple clamp  26  and lower triple clamp  28 . Optionally, the steering shaft may couple to the upper triple clamp and the lower triple clamp without the perpendicular relationship. The steering shaft includes an upper end  52  that is adapted to couple to the upper triple clamp and a lower end  54  that is adapted to couple to the lower triple clamp. The steering shaft is held securely to the frame via bearings (not shown). Although the steering shaft is shown to be cylindrical, the steering shaft may also be a rectangular prism or other suitable geometry. 
     The lower triple clamp  28  may be similar in shape to the upper triple clamp  26 , and is oriented substantially parallel to the upper triple clamp. The lower triple clamp may be thicker (greater in height) than the upper triple clamp for the inclusion of bearing pockets and bearings (not shown) (not to be confused with bearings coupling the steering shaft to the frame). The bearing pockets are located on a front side and a back side of the lower triple clamp to house two bearings. The bearings permit the pivot shaft to rotate and support the load that acts on the suspension assembly. 
     The lower end  54  of the steering shaft  24  rests in the middle of the lower triple clamp  28  between the two retention braces  56 . The lower end may be adapted to allow pivotal movement in the lateral direction about a pivot axis A, and/or the lower triple clamp provides a small clearance so that the lower triple clamp can pivot about axis A. This range of pivotal motion is limited by the flexibility or rigidity of the spring unit  30  located at the other end of the steering shaft. It may be little or no movement if the spring unit is very rigid or several degrees if the spring is less rigid or comprised of flexible material. 
     As mentioned above, when a typical motorcycle enters an orientation during travel where there is little or no dampening, such as when it is leaning over at a great angle, the motorcycle may chatter and decrease front wheel contact to the road surface. The suspension assembly may solve this problem by providing lateral flex to the motorcycle without compromising the rigidity necessary for hard braking. By decoupling the longitudinal and lateral forces, the suspension assembly allows the absorption of lateral forces and restores front wheel contact in less time. 
     Further, the front end may pivot about pivot axis A and at the same time, rotate about a steering axis B for steering of the motorcycle. In addition, steering stops  58  may be coupled to the lower triple clamp  28  to limit the range of motion in steering about axis B. 
     Turning to  FIG. 8 , one embodiment of the suspension assembly  20  is shown in exploded view. As described above, the suspension assembly includes upper triple clamp  26 , a lower triple clamp  28 , and steering shaft  24  coupling the upper triple clamp to the lower triple clamp. The upper triple clamp and the lower triple clamp are substantially parallel to each other and the steering shaft is substantially perpendicular to the triple clamps. Alternatively, the steering shaft need not be substantially perpendicular to the triple clamps. The steering shaft is coupled to bearings which secure it to the frame of the motorcycle. 
     The suspension assembly  20  further includes a spring unit  30  coupling the upper triple clamp  26  and the steering shaft  24  together, and may serve to absorb forces that may be transferred from the upper triple clamp to the steering shaft and vice versa. The spring unit also inherently gives strength to the suspension assembly, in addition to the strength provided by the bearings, as further discussed below. 
     The upper end  52  of the steering shaft may include a shoulder  60  to assist in supporting the spring unit and other components for ease of coupling. Other components that may be located in this area include bearings (not shown) and lock nuts for connecting the steering shaft securely to the steering tube and frame. 
     The suspension assembly  20  further includes a pivot mechanism  62 . As shown, the pivot mechanism may be a pivot shaft inserted through two bearings  64  located in bearing pockets  66  located in the lower triple clamp and secured by a pivot nut  68 . The pivot shaft rotates with the bearings, which may bear much of the load that acts on the suspension assembly. The bearings help in maintaining longitudinal stiffness. Bolts  70  attach a steering shaft cap  72  to the lower end of the steering shaft, thus surrounding the pivot shaft and holding the pivot shaft so that the steering shaft can pivot with the pivot shaft. 
     Alternatively, the steering shaft may pivot on a different kind of pivot mechanism. For example, a ball and socket joint pivot mechanism may be used where the steering shaft may include a socket that swivels on a ball. The steering shaft or the lower triple clamp may include stops or geometry to allow only one plane of motion of the steering shaft as it swivels. 
       FIG. 9  is an alternate embodiment of the suspension assembly  21  as shown in exploded view. This embodiment of the suspension assembly is similar to the embodiment pictured in  FIG. 8 , and may include different designs of different components of the suspension assembly. The design variations do not change the general functionality of the suspension assembly, but instead offer an alternate way of constructing the suspension assembly. The design variations may include structural differences of the upper triple clamp, lower triple clamp, spring unit, and steering shaft. Some of these design variations are readily visible from the depiction of  FIG. 9 . 
     One of these design variations is the location of the bearing pockets for the coupling with the bearings and pivot mechanism. Instead of housing the bearings in the lower triple clamp, the bearings may be housed in the lower end  54  of the steering shaft at  74 . The scope of the invention includes other adaptations of the steering shaft to allow for configurations that are conducive to effectuate absorption of lateral forces acting on the front end. 
     Further, the suspension assembly of  FIGS. 8 and 9  may include the components illustrated in  FIGS. 8 and 9  and although not mentioned, any washers, spacers, o-rings, seals, screws, nuts and bolts, fasteners and other components that may aid in the function of the suspension assembly. Optionally, dust seals may be included to prevent debris from entering the suspension assembly. 
     Referring to  FIGS. 10-11 , an exemplary spring unit for use in one embodiment of the suspension assembly is shown at  76 .  FIGS. 12-15  show exemplary spring units that may be used with alternate embodiments of the invention. Typically the spring units couple with the upper triple clamp. Alternatively, the spring units may couple with the lower triple clamp. As illustrated in a perspective view in  FIG. 10 , the spring unit  76  may be constructed with an annular frame  78  including two ribs  80  each connecting the annular frame with a center ring  82 . The center ring includes an attaching surface  84  to bolt the upper triple clamp  26  (not shown) to the steering shaft  24  (not shown). In this figure, the attaching surface is shaped as a square with rounded corners. 
     As shown, where the ribs connect to the annular frame and to the center ring, the junctions  86  are filleted. The radius of the fillets may be varied to change the strength and rigidity of the spring unit. 
     It may be desirable to have extra strength in the longitudinal direction to withstand braking forces. By orienting the spring unit such that the ribs are aligned longitudinally, this can be achieved. For alignment, the spring unit may include a mechanism which allows for aligning the spring unit to a particular orientation. The mechanism may be placement of multiple holes, a square-shaped bolt hole, or other indicator for alignment. Multiple holes  88  may be adapted for fasteners to insert through and couple the spring unit to the upper triple clamp. 
       FIG. 11  shows an exaggerated top view of the spring unit of  FIG. 10  undergoing flex as a spring. The ribs  80  and the center ring  82  may be displaced in the lateral direction (in this view, left and right) as well as in the vertical direction (in this view, into the page and out of the page). The ribs and the center ring may be displaced in a direction opposite than what is pictured as well. While the spring unit is flexing to absorb energy, the lateral forces distribute between the two ribs. When the forces have been absorbed, the spring unit returns to a neutral position such as shown in  FIG. 10 . The deflection in the spring unit is exaggerated for illustrative purposes. 
     Referring to  FIG. 12 , a spring unit suitable for use with another embodiment of the suspension assembly is shown at  88 . The spring unit may be solid and constructed of a single material (shaded in the figure), thus the ribs as described above may be used, but are not required. As an alternative, if increased lateral stiffness is desired, the spring unit may be a rigid, solid block that does not exhibit characteristics of a spring. This offers the option of switching back to a conventional suspension system without having to dismantle and rebuild the front end in its entirety. 
     As illustrated in  FIG. 12 , the attachment means from the upper triple clamp to the spring unit may be different. For example, multiple holes for alignment or coupling to the upper triple clamp may be tapped for bolts to screw in from the top as shown as  90 . In another example, the spring unit may include a raised concentric ring  92  with the outer circumference  94  threaded. In addition, the attaching surface as described in  FIG. 10  is circular shaped in this embodiment of the spring unit. Further, the attaching surface may be tapered as shown at  96 . 
     Referring now to  FIG. 13 , a spring unit  98  for use with an alternate embodiment may include an annular frame  100  with a center ring  102 , similar to  FIG. 12 , with a vacant region  104  in between. Different materials for dampening may fill in the vacant region for improved absorption. These materials may include rubber neoprene, air or nitrogen bladders, honey-combed structures and the like, anisotropic materials, and other dampening materials. By changing the material, the dampening characteristics may be tuned to the desired amount and strengthened in the desired direction (generally longitudinally) 
     The vacant region may further include ribs that may flex, for example, such as shown in  FIG. 11 . In an alternate embodiment, the vacant region may include more ribs, different rib widths, lengths and thicknesses, radial and other rib arrangements, and varying fillet radii, in addition to dampening materials mentioned above. 
     Turning to  FIG. 14 , in an alternate embodiment of the suspension assembly, a torsion rod  106  may be used to strengthen a spring unit  108  in the longitudinal direction. The spring unit may include an annular frame  110  with a center ring  112  and a passage  114  adapted for placement of the torsion rod. The passage is oriented parallel to the ribs  116 , and cuts through the ribs and center ring. The torsion rod may include detents  118  spaced apart that assist in holding the torsion rod in place after the torsion rod is inserted in the spring unit. The torsion rod may be composed of titanium, steel, carbon fiber, aluminum or a more rigid material while the frame, ribs, and ring portions may be composed of aluminum or a different material. 
     It should be noted that the spring unit does not necessitate an annular frame with center ring formation. The spring unit may have a different geometry, and still function similarly to the spring units as described. The center rings as shown in the spring units above may not need to be centered, concentric, or ring-shaped. For example,  FIG. 15  shows a spring unit without an annular frame that may be used with an alternate embodiment of the suspension assembly. The spring unit includes a cylinder  122  with a hollow  124  in the shape of a cross. The spring unit further includes a spacer  126  shaped to fit inside the hollow and accommodate coil springs  128 . The coil springs are positioned in the same orientation to enable the spacer to move in one general direction. The cylinder  122  and the spacer  126  may include shallow beds  130  which seat the coil springs and keep them in place during operation. In this configuration of the spring unit, the coil springs may be swapped with other springs to adjust to the desired flexibility of the spring unit. On certain inner surfaces of the spring unit where the spacer may contact directly, a coating such as a fluoropolymer or friction-reducing material may be applied. 
     The spring units as described may be alternatively constructed with different shapes or characteristics to enable the suspension assembly to function as desired. It is within the scope of the invention for a spring unit to use a polygonal or elliptical frame instead of an annular frame. Further, the suspension assembly allows for adjustable lateral stiffness by swapping a spring unit with certain characteristics for another one with different characteristics. 
     Additionally, these spring units may be partially or wholly manufactured out of aluminum, steel, titanium, carbon fiber or other suitable materials that may exhibit elastic properties and have sufficient tensile strength to withstand forces inflicted on the front end. Further, there may be other suitable materials, thicknesses, and variations of the geometry well within the scope of the invention to provide the desired longitudinal and lateral stiffness of the front end. 
     As shown in  FIG. 16 , an alternate embodiment of the suspension assembly  132  may include locating a pivot mechanism  134  in an upper triple clamp  136  while a spring unit  138  is located in the lower triple clamp  140 . Both the pivot mechanism and the spring unit are coupled to a steering shaft  142 . The principle of operation is the same in that when the motorcycle is leaning, the forces may transfer similarly and allow the suspension assembly to absorb lateral forces by pivoting about an axis C. Normal steering is unhindered as rotation of steering axis D is allowed. 
     As shown in  FIGS. 17 ,  18 , and  19 , in another alternative suspension assembly  150  an upper triple clamp  152  includes a shaped plate, such as a cast or machined metal member including a retention brace  154  on each lateral side, for retaining and securing front forks  34 ,  36  (not shown). In the middle of the upper triple clamp  152  is an aperture  156  in which a spring unit  158  is located. A movable end  159  of the spring unit  158  defines a receptacle  162  into which a steering shaft  160  extends, as may be seen better in  FIGS. 18 and 19 . A fastening bolt  164  extends through the receptacle  162  of the spring unit  158  into a threaded bore  166  in the steering shaft  160  to securely fasten the upper end  168  of the steering shaft  160  to the movable end  159  of the spring unit  158 . 
     As with the previously described embodiments of the suspension system disclosed herein, the steering shaft  160  is disposed substantially perpendicular to the upper triple clamp  152  and to a lower triple clamp  172 . The lower triple clamp  172  may be similar in shape to the upper triple clamp  152  and is oriented substantially parallel to the upper triple clamp  152 . The lower triple clamp  172  may also include bearing pockets and bearings (not shown) to receive a pivot shaft of a pivot mechanism (not shown) oriented generally longitudinally (of the suspension assembly, and thus of the vehicle) so as to define a pivot axis E. 
     The pivot shaft, similar to the pivot shaft shown in the pivot mechanism  62  in  FIG. 8 , may be clamped to the lower end of the steering shaft  160  by a clamp  174 , so that the central axis F of the steering shaft  160  intersects the pivot axis E of the pivot mechanism, as shown in  FIG. 17 . Since the attachment of the lower end of the steering shaft  160  to the pivot mechanism by the clamp  74  is generally similar to that shown in  FIGS. 7 and 8 , the manner of attachment is not shown in detail here. By virtue of the pivot mechanism the lower triple clamp  172  is able to rotate about the axis E through a limited angle permitted by the clearance between the lower triple clamp  172  and the clamp  174  in response to lateral forces acting upon the forks of the front suspension. 
     Referring to  FIG. 18 , the movable end  159  of the spring unit  158  may include an inwardly protruding annular ledge  178  to be clamped between the head of the bolt  164  and the upper end  168  of the steering shaft  160  in order to securely attach the upper end  168  to the movable end  159 . 
     A mounting portion  180  of the spring unit  158  is located longitudinally opposite the movable end  159  and includes a pair of oppositely laterally directed arms  182  each defining a mounting bolt hole  184 . 
     Extending longitudinally between the movable end  159  and the mounting portion  180  of the spring unit  158  are a pair of resiliently flexible ribs  186 ,  188 . The ribs  186 ,  188  may have similar widths or thicknesses  190  and depths  192 , and the length  194  of each rib  186  and  188  extends longitudinally with respect to the front suspension assembly  150 . It will be understood that the compliance or flexibility of the spring unit  158  will be variable by changing the thickness  190 , depth  192 , or separation distance  196  between the ribs  186  and  188 , or by varying the material of which the spring unit  158  is made. 
     As may be seen in  FIGS. 19 and 20 , the spring unit  158  fits in the under side of the upper triple clamp  152 , with each of the arms  182  fitting into a respective stall  198 . Fitted mounting screws  200  extend into threaded bores  202  to fasten the spring unit  158  securely into place in the upper triple clamp  152 . As shown best in  FIG. 19 , there is room provided in the upper triple clamp  152  to place a mounting screw  200  in line with the threaded bore  202 , and an access opening  204  allows the use of a suitable wrench to tighten the mounting screw  200  in place, extending through a fitted bore  205  in a web of the upper triple clamp  152  and the respective bolt hole  184 , into the threaded bore  202 . 
     The aperture  156  in the upper triple clamp  152  is large enough to provide a gap  206  around the movable portion  159  of the spring unit  158 , so as to permit movement of the movable portion  159  laterally in either direction as indicated by the arrow  208 , as the ribs  186  and  188  are flexed by lateral forces acting on the front forks  34 ,  36  of the front end and urging the upper and lower triple clamps  152  and  172  to move about the pivot axis E. The width  210  of the gap  206  may be used to control the maximum flexure of the spring ribs  186  and  188  so as to allow a desired amount of lateral flexure of the suspension assembly  150  so as to reduce chatter yet without sacrificing control, as the upper end  168  of the steering shaft  160  is permitted to move in the direction indicated by the arrow  208  through only the distance provided by the width  210  of the gap  206 . It will be appreciated that during heavy braking of the front wheel of a motorcycle equipped with a suspension assembly  150  the ribs  186  and  188  of the spring unit  158  will be in tension and thus will tend to be centered by pendulum forces. It will also be appreciated that, as in the suspension assembly  132  shown in  FIG. 16 , a spring unit  158  could be appropriately mounted in a lower triple clamp and a pivot mechanism could be used to couple the steering shaft  160  to an upper triple clamp. 
     A spring unit  212 , shown in  FIGS. 22 and 23 , is generally similar to the spring unit  158 , but its ribs  186 ′ and  188 ′ have a depth  192 ′ greater than the depth  192  of the ribs of the spring unit  158 , so that the spring unit  212  is stiffer than the spring unit  158  if made of similar material and if the other dimensions are similar. The spring unit  212  thus might be more appropriate for a heavier motorcycle. 
     All of the disclosed components of the invention may each embody different features as described that may provide advantages in manufacture and assembly. Some of the features may be mixed and matched on another embodiment of the invention and still be within the scope of the present invention. 
     While the invention has been described with reference to its use in a motorcycle, the invention is not limited to motorcycles, but can be used in bicycles, dirt bikes, and other vehicles. Further, the invention may be used with an “upside-down” suspension fork, or it may alternatively be used with a traditional telescopic fork or a rigid fork. 
     Some components have been illustrated as being of monolithic construction, while other components have been illustrated as being separate components coupled together. It is within the scope of the invention to combine these components or separate them due to design and manufacturing considerations. For example, the steering shaft may be constructed in multiple pieces for ease in manufacturing. The lower end of the steering shaft may be separately constructed as a block and coupled to a threaded end of the steering shaft, and still allowing functionality like the steering shaft as pictured. As another example, it is feasible for the spring unit to be integrally constructed or permanently attached to the upper triple clamp or the lower triple clamp. This may offer the benefit of obviating the need for alignment or additional assembly. 
     The skilled reader will further appreciate that the invention may be practiced in a “single-sided” front end, such as that found on some bicycles which have only a single fork. The term “triple clamp” should not necessarily be interpreted to mean that two forks are required with the steering shaft. For example, one of the two forks may be coaxial to the steering shaft or considered to be the steering shaft and the other fork and the front end may pivot about the lower end of the steering shaft. The presence of one or more springs or dampers coaxial to or coupled to the steering shaft does not necessarily prohibit the additional presence of one or more springs or dampers elsewhere, such as within the forks. 
     The various features illustrated in the figures may be combined in many ways, and should not be interpreted as though limited to the specific embodiments in which they were explained and shown. Those skilled in the art having the benefit of this disclosure will appreciate that many other variations from the foregoing description and drawings may be made within the scope of the present invention. 
     The terms and expressions which have been employed in the foregoing specification are used therein as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding equivalents of the features shown and described or portions thereof, it being recognized that the scope of the invention is defined and limited only by the claims which follow.