Patent Publication Number: US-10328991-B2

Title: Bicycle frame with passive seat tube pivot joint

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present invention claims priority to U.S. Provisional Patent Application Ser. No. 61/430,011 filed on Jan. 5, 2011 and the disclosure of which is expressly incorporated herein. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to bicycles and, more particularly, to a bicycle frame assembly wherein the seat tube is connected at an overlapping intersection of a top tube and the seat stays by a passive pivot that allows the seat stay to deflect from a generally linear at-rest orientation to improve the vertical compliance of the bicycle frame. 
     The primary structural component of a conventional two-wheel bicycle is the frame. On a conventional road bicycle, the frame is typically constructed from a set of tubular members assembled together to form the frame. For many bicycles, the frame is constructed from members commonly referred to as the top tube, down tube, seat tube, seat stays and chain stays, and those members are joined together at intersections commonly referred to as the head tube, seat post, bottom bracket and rear dropout. The top tube usually extends from the head tube rearward to the seat tube. The head tube, sometimes referred to as the neck, is a short tubular structural member at the upper forward portion of the bicycle which supports the handlebar and front steering fork, which has the front wheel on it. The down tube usually extends downwardly and rearward from the head tube to the bottom bracket, the bottom bracket usually comprising a cylindrical member for supporting the pedals and chain drive mechanism which powers the bicycle. The seat tube usually extends from the bottom bracket upwardly to where it is joined to the rear end of the top tube. The seat tube also usually functions to telescopically receive a seat post for supporting a seat or saddle for the bicycle rider to sit on. 
     The chain stays normally extend rearward from the bottom bracket. The seat stays normally extend downwardly and rearward from the top of the seat tube. The chain stays and seat stays are normally joined together with a rear dropout for supporting the rear axle of the rear wheel. The portion of the frame defined by the head tube, seat post and bottom bracket and the structural members that join those three items together can be referred to as the main front triangular portion of the frame, with the seat stays and chain stays defining a rear triangular portion of the frame. The foregoing description represents the construction of a conventional bicycle frame which of course does not possess a suspension having any shock absorbing characteristics. 
     Although the increased popularity in recent years of off-road cycling, particularly on mountains and cross-country, has made a shock absorbing system in many instances a biking necessity. An exemplary rear wheel suspension system is disclosed in U.S. Pat. No. 7,837,213. Generally, bicycle suspension systems intended for off-road riding conditions include a number of links that are connected and movable or pivotable to allow the bicycle frame to absorb a portion of the energy associated with aggressive riding over uneven terrain. However, such robust suspension systems do not particularly lend themselves to extended rides over paved terrain. The robust nature of such systems increases the weight attributable to the bicycle assembly. During rides intended to test rider stamina, endurance, and conditioning, such robust suspension systems would detrimentally affect rider time performance. 
     Fixed shape forward and rear triangle frame shapes are generally well accepted as the preferred configuration for many road bicycles due to their collective light weight and robust frame. However, even paved surfaces can present discontinuities wherein most riders would prefer some degree of bicycle suspension to limit or reduce the forces communicated to the rider from payment discontinuities. The ever increasing capabilities of bicyclists have created a sub-set of the road bicycle termed an endurance bicycle. Endurance bicycles are generally understood as race-ready road bicycles with added comfort to allow riders to complete rides of ever increasing duration and/or distance. Many endurance bicycles maintain a fixed forward and rear triangle frame and provide impact dampening with suspension seat posts and/or vibration dampening handlebar assemblies. 
     An alternate approach to an endurance bicycle is disclosed in U.S. Pat. No. 6,932,371. U.S. Pat. No. 6,932,371 discloses a bicycle assembly wherein the seat tube forms a passive suspension element via the elimination of the seat stays and providing a second set of chain stays that are located in closer proximity to the bottom bracket that to the top tube. The frame assembly of U.S. Pat. No. 6,932,371 includes a number of gusset members that are required to provide the desired non-vertical stiffness of the frame assembly. In achieving the desired vertical compliance, the bicycle frame of U.S. Pat. No. 6,932,371 includes a number of supplemental structures that, in improving vertical compliance, detrimentally affect the overall weight of the underlying bicycle assembly. 
     Accordingly, there is a desire to provide a bicycle frame assembly that includes a passive suspension element but does not appreciably detrimentally affect the weight of the overall bicycle frame assembly. 
     BRIEF DESCRIPTION OF THE INVENTION 
     The present invention provides a bicycle frame assembly having a deflectable seat tube that overcomes one or more of the aforementioned drawbacks. One aspect of the invention discloses a bicycle frame assembly having an upper frame member and a lower frame member. The upper frame member includes a top tube and a pair of seat stays and extends between a dropout and a head tube in a generally continuous manner. The lower frame member includes a bottom tube, a bottom bracket, and a chain stay and extends between the dropout and the head tube. A seat tube extends from the lower frame member toward the upper frame member and passes beyond the top tube. The seat tube is connected to the upper frame member by a pivot so that more of the seat tube is located between the pivot and the bottom bracket than extends beyond the upper frame member. Preferably, an opening is formed through the top tube or a lug that connects the seat stays with the top tube. The seat tube preferably passes through the opening in the upper frame member. Alternatively, the seat tube could be perforated or otherwise contoured to pass generally around the more horizontal structure of the top tube and/or the seat stays. As another alternative, the seat tube could pass rearward relative to the top tube so as to be positioned in the space generally flanked by the seat stays. 
     Another aspect of the invention that is useable with one or more of the above aspects discloses a bicycle frame assembly that includes a forward frame triangle that includes a top tube and a bottom tube. The top tube includes a first end that is connected to a head tube and a second end. The bottom tube includes a first end that is connected to the head tube and a second end. A bottom bracket is connected to the second end of the bottom tube. A seat tube extends in an upward direction from the bottom bracket and a pair of seat stays is connected to the top tube and extends in a rearward direction beyond the forward frame triangle. A pivot connects the seat tube to the forward frame triangle proximate the top tube at a location nearer a bicycle seat than the bottom bracket. The pivot allows that portion of the seat tube disposed between the pivot and the bottom bracket to deflect from an at rest position during vertical loading of the seat tube. 
     Another aspect of the invention that is useable with one or more of the above aspects discloses a bicycle frame assembly having an upper frame member that includes a top tube and a pair of seat stays. The upper frame member extends between a dropout associated with a rear wheel and a head tube. An opening is formed in the upper frame member. A lower frame member that includes a bottom tube, a bottom bracket, and a chain stay extends between the dropout and the head tube. A seat tube extends from the lower frame member toward the upper frame member and passes through the opening in the upper frame member. A pivot connects the seat tube to the upper frame member proximate the opening so that more of the seat tube is located between the pivot and the bottom bracket than extends beyond the upper frame member. 
     Another aspect of the invention that is useable with one or more of the above aspects discloses a method of allowing deflection of a seat tube. A seat tube is connected to a bottom bracket. The seat tube is connected to an upper frame member with a pivot that is located at an overlapping intersection of the seat tube and the upper frame member so that the seat tube can deflect from alignment along a line between the bottom bracket and the pivot. 
     These and various other features and advantages of the present invention will be made apparent from the following detailed description and the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The drawings illustrate one preferred embodiment presently contemplated for carrying out the invention. 
         FIG. 1  is a side elevation view of a bicycle having a bicycle frame assembly according to the present invention; 
         FIG. 2  is an elevated right hand perspective view of bicycle frame assembly shown in  FIG. 1  with the wheels, seat, drive and handlebar assemblies removed therefrom; 
         FIG. 3  is a view similar to  FIG. 2  of an intersection of the seat tube with the upper frame member of the bicycle frame assembly shown in  FIG. 1 ; 
         FIG. 4  is a cross-section of the intersection of the seat tube with the upper frame member taken along line  4 - 4  shown in  FIG. 3 ; 
         FIG. 5  is an exploded view of the assembly associated with the intersection of the seat tube and the upper frame member shown in  FIG. 3 ; and 
         FIG. 6  is a side elevation view of the bicycle frame assembly shown in  FIG. 2  and shows the loaded and loaded configurations of the seat tube associated with use of the bicycle frame assembly. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIG. 1  shows a bicycle  10  having a frame assembly  12  according to the present invention. Bicycle  10  includes a seat  16  and handlebars  18  that are attached to frame assembly  12 . A seat post  20  is connected to seat  16  and slidably engages a seat tube  22  of frame assembly  12 . A top tube  24  and a down tube  26  extend forwardly from seat tube  22  to a head tube  28  of frame  12 . Handlebars  18  are connected to a stem or steer tube  30  that passes through head tube  28  and is connected or integrally formed with a fork crown  32 . Understandably, handlebar  18  may include a stem that is constructed to slidably engage an interior cavity of steer tube  30 . It is appreciated that one or more of the structures of bicycle  10  and frame assembly  12  can be constructed from similar materials, a variety of different materials, and various combinations thereof. Preferably, frame assembly  12  and seat tube  22  are formed of metal-type materials, such as aluminum-type materials, carbon fiber materials, and/or materials that are sufficiently formable and robust enough to support the rider of bicycle  10 . 
     Fork assembly  14  includes a pair of fork blades or fork legs  34  that extend from generally opposite ends of fork crown  32  and are constructed to support a front wheel assembly  36  at an end thereof or dropout  38 . Dropouts  38  engage generally opposite sides of an axle  40  constructed to engage a hub  42  of front wheel assembly  36 . A number of spokes  44  extend from hub  42  to a rim  46  of front wheel assembly  36 . A tire  48  is engaged with rim  46  such that rotation of hub  42  and rim  46 , relative to fork legs  34 , rotates tire  48 . 
     Bicycle  10  includes a front brake assembly  50  having an actuator  52  attached to handlebars  18  and a pair of brake pads  53  positioned on generally opposite sides of front wheel assembly  36 . Brake pads  53  are constructed to engage a brake wall  54  of rim  46  thereby providing a stopping or slowing force to front wheel assembly  36 . A rear wheel assembly  56  includes a brake assembly  58  similar to front wheel brake assembly  50  but it is appreciated that one or both of front and rear wheel brake assemblies  50 ,  58  could be provided in other brake configurations such as a disk brake assembly wherein a rotor and a caliper are positioned proximate one or more of front wheel axle  40  or a rear axle  64 , respectively. A rear wheel  66  is positioned generally concentrically about rear axle  64 . 
     A pair of seat stays  62 ,  68  ( FIG. 2 ) and a pair of chain stays  70 ,  71  ( FIG. 2 ) extend rearward relative to seat tube  22  and offset rear axle  64  from a crankset  72 . Crankset  72  includes a set of pedals  74  that is operationally connected to a flexible drive member such as a chain  76  via one or more variable diameter chain gears or a chain ring or sprocket  78 . Rotation of chain  76  communicates a drive force to a gear cluster  80  positioned proximate rear axle  64 . Gear cluster  80  is generally concentrically orientated with respect to rear axle  64  and includes a number of variable diameter gears. 
     Gear cluster  80  is operationally connected to a hub  82  of rear wheel  66 . A number of spokes  84  extend radially between hub  82  and a rim  86  of rear wheel  66  of rear wheel assembly  56 . As is commonly understood, rider operation of pedals  74  drives chain  76  thereby driving rear wheel  66  which in turn propels bicycle  10 . Fork assembly  14  is constructed to support a forward end  88  of bicycle  10  above a ground surface  90 . Handlebar  18  is connected to frame  12  and fork assembly  14  such that operator manipulation of handlebar  18  is communicated to fork assembly  14  to facilitate rotation of front wheel assembly  36  relative to frame assembly  12  along a longitudinal axis, indicated by arrow  175 , of bicycle  10 . As is commonly understood, such manipulation of handlebar  18  steers bicycle  10  during riding. 
     Understandably, the construction of bicycle  10  shown in  FIG. 1  is merely exemplary of a number of bicycle configurations. That is, whereas bicycle  10  is shown as what is commonly understood as a street or road bike, it is appreciated that the present invention is applicable to a number of bicycle configurations including those bicycles with more aggression suspension systems commonly found in off-road or mountain bike frame configurations, and/or hybrids, cross-over or multi-purpose bicycle frame configurations. 
     Referring to  FIGS. 1 and 2 , top tube  24  and seat stays  68  extend in a fairly continuous manner to form an upper frame member  100  that extends from head tube  28  to a pair of dropouts  102 ,  103  that support rear axle  64 . Upper frame member  100  can be formed as one piece and/or assembled from a distinct top tube  24 , seat stays  68 , and/or an optional lug  104  that is disposed between the top tube  24  and the seat stays  68 . It is appreciated that seat stays  62 ,  68  and top tube  24  of upper frame member  100  could be formed as a unitary structure, a number of discrete permanently connected elements, or connected to one another via an optional lug  104  associated with an overlap area  105  of seat tube  22  and upper frame member  100 . In a similar manner, it is also appreciated that down tube  26 , bottom bracket  110 , and chain stays  70 ,  71 , whose assemblies collectively define a lower frame member that extends from head tube  28  to one or more dropouts  102 ,  103  could be formed as a unitary assembly wherein bottom bracket  110  is formed with down tube  26  or chain stays  70 ,  71 , or an assembly wherein the chain stays  70 ,  71  and down tube  26  can be permanently affixed to a discrete bottom bracket lug or simply bottom bracket  110 . Once assembled, as plainly shown in  FIG. 1 , bicycle  10  includes a forward frame triangle that is a generally defined by the triangular shape of the direction of extension of the seat tube, the top tube, and the down tube of frame assembly  12  regardless of the methodology or number of discrete elements used to form the frame assembly. 
     As shown in  FIG. 2 , seat tube  22  includes a first end  108  that is secured to bottom bracket  110  of bicycle frame  12  and a second end  112  that extends in a generally upward direction beyond the location of the lug or overlap area  105  with upper frame member  100 . Preferably, seat post  20  ( FIG. 1 ) telescopically cooperates with seat tube  22  of frame assembly  12 . A passive pivot assembly  120  connects an upper portion of seat tube  22  to bicycle frame assembly  12  proximate overlap area  105  such that more of seat tube  22  extends between pivot assembly  120  and bottom bracket  110  than extends in an upward direction relative to the intersection of seat tube  22  and upper frame member  100 . 
     Passive pivot assembly  120  completes the linkage between upper frame member  100 , which includes top tube  24  and the structures associated with seat stays  62 ,  68 . A lower end of seat tube  22  is secured to lower frame member  101 , which includes the down tube  26  and bottom bracket  110  and preferably one of more chain stays  70 ,  71 . As explained above, seat tube  22 , top tube  24  and down tube  25  collectively generally define the forward triangle of frame assembly  12 . Frame assembly  12  has a fairly robust and stable feel during use but is also constructed to provide impact dampening performance in a manner that does not allow changing of the relative connection points of any of the respective members of the forward frame triangle. As described further below with respect to  FIG. 6 , the non-bonded rigid yet pivotable connection of seat tube  22  with upper frame member  100  allows deflection of seat tube  22  in a vertical plane and in a direction along the longitudinal length of the seat tube  22  so as to allow the frame assembly  12  to provide a limited degree of suspension performance or vertical compliance without altering the orientation of the connection points of any of the frame members relative to one another. 
     As shown in  FIGS. 3-5 , overlap area  105  includes a passage  130  that is shaped to allow seat tube  22  to pass therethrough. An opening  132  ( FIG. 5 ) is formed laterally through seat tube  22  and shaped to rotationally cooperate with pivot assembly  120 . As mentioned above, it is envisioned that seat tube  22  merely pass over an axis or longitudinal area associated with one or more of the top tube, the seat stays, and/or a fabrication lug being formed therebetween. It is envisioned that the seat tube could be perforated or otherwise contoured to pass generally around the more horizontal structure of the top tube and/or the seat stays associated with upper frame member  100 . As another alternative, the seat tube could pass rearward relative to the closed structure of top tube  24  so as to be positioned in the space generally flanked by the seat stays. Each configuration allows limited passive pivoting between seat stays  70 ,  71  and the adjacent structure of upper frame member  100  of bicycle frame assembly  12 . 
     As shown in  FIG. 3 , passage  130  is bounded on a forward side  131  by an end wall associated with top tube  24  or a portion of the respective frame lug  104 . A first optional gasket  134  is disposed between forward side  131  of overlap area  105  and top tube  24  and generally surrounds a forward side  136 , and opposite lateral sides  138 ,  140  of seat tube  22 . Optional gasket  134  prevents moisture and/or dirt and/or debris from entering the pivot area associated with passage  130  and the passage of seat tube  22  therethrough but does not otherwise interfere with the flexion of seat tube  22  during use of bicycle  10  as described further below with respect to  FIG. 6 . Passage  130  is bounded on opposite lateral sides by side walls  142 ,  144  of upper frame member  100 . An optional rear web wall  146  completes the definition of passage  130  such that upper frame member  100  completely surrounds seat tube  22  with web wall  146  extending laterally between seat stays  62 ,  68 . 
     As shown in  FIGS. 4 and 5 , pivot assembly  120  includes a first bolt or other fastener  150 , a second bolt or other fastener  152 , a guide sleeve  154 , and first and second bearings or bushings  156 ,  158 . Each of fasteners  150 ,  152  includes a threaded portion  160 , a stem portion  162 , and a head portion  164 . The radial diameter of each fastener  150 ,  152  gradually increase from the respective threaded portion  160  to the stem portion  162  to the head portion  164 . One or each of head portions  164  includes a drive surface  166  that is shaped to cooperate with a driving tool, such as a hex driver or the like for securing each of first and second fasteners  150 ,  152  relative to pivot assembly  120 . Although shown as being formed on an interior radial surface of fasteners  150 ,  152 , it is appreciated that driving surface  166  could have any number of shapes and/or be provided on a radial exterior surface of the corresponding fastener  150 ,  152 . It is further appreciated that one of fasteners  150 ,  152  could formed integrally with sleeve  154  such that operation of one respective fastener secures pivot assembly  120  relative to bicycle frame assembly  12 . 
     Each bushing  156 ,  158  includes an outer radial surface  170 , an inner radial surface  172 , an outboard lateral surface  174 , and an inboard lateral surface  176 . As used herein, the inboard and outboard lateral directions associated with surfaces  174 ,  176  of each bushing  156 ,  158  refers to the orientation of surfaces  170 ,  174  relative to a longitudinal vertical plane that contains longitudinal axis  175  of bicycle  10  and the relative position of the respective surfaces and/or structures relative to the same. For example, surfaces  176  of bushings  156 ,  158  are nearer a longitudinal axis, indicated by line  178 , of upper frame member  100 . Accordingly, surfaces  174  are further outboard and surfaces  176  are further inboard relative to one another and longitudinal axis  178  of upper frame member  100  along a longitudinal axis, indicated by line  180 , of pivot assembly  120 . As shown in  FIG. 5 , the longitudinal axis  180  of pivot assembly  120  is oriented in a crossing direction relative to, and is preferably normal to, longitudinal axis  178  of upper frame member  100 . 
     Still referring to  FIGS. 4 and 5 , a first opening  184  and the second opening  186  are formed in each of the respective sidewalls  142 ,  144  of upper frame member  100  and centered along axis  180  of pivot assembly  120 . A seat  188  extends circumferentially about at least one of openings  184 ,  186  in the lateral outboard facing surface of the respective sidewall  142 ,  144 . Seat  188  is defined by a lip  190  that extends circumferentially about the corresponding opening  184 ,  186  and is shaped to cooperate with sleeve  154  and a corresponding bushing  156 ,  158 . 
     Sleeve  154  includes a stem portion  194 , the head portion  196 , and an opening  198  formed therethrough. Sleeve  154  is constructed to slidably cooperate with openings  184 ,  186  in a direction aligned with axis  180 . When assembled, head portion  196  of sleeve  154  traverses an overlapping area between opening  184  and a seat  199  associated with opening  132  of seat tube  22  as well as opening  200  associated with optional gasket  134 . Optional gasket  134  includes a second opening  202  that, when assembled, is also concentrically oriented with respect axis  180  of pivot assembly  120  and cooperates with the other of fasteners  150 ,  152 . Opening  132  of seat tube  22  circumferentially cooperates with stem portion  194  of sleeve  154  when the longitudinal axis of opening  132  is aligned axis  180  of pivot assembly  120 . As explained further below with respect to  FIG. 6 , the axis of opening  132  of seat tube  22  is formed along a plane, indicated by line  204 , that is offset in a forward direction relative to longitudinal axis  175  of bicycle  10  and with respect to a longitudinal axis  206  of seat tube  22 . 
     Threaded portions  160  of each fastener  150 ,  152  operatively cooperate with a threaded surface  210  ( FIG. 4 ) formed on an inner radial surface of sleeve  154 . Bushings  156 ,  158  rotatably cooperate with stem portion  162  of each of fasteners  150 ,  152  and cooperate with seats  188  defined by upper frame member  100 . As shown in  FIGS. 4 and 5 , pivot assembly  120  can include another optional gasket  214  that cooperates with the laterally outboard directed sides of pivot assembly  120 . Gasket  214  includes a first arm  216  and a second arm  218  that extend in a generally upward direction relative to a web wall  220 . The laterally inboard facing side of each arm  216 ,  218  includes a lip  221  that is shaped to snuggly cooperate with a radially outboard directed surface of head portion  164  of a respective fastener  150 ,  152 . Preferably, upper frame member  100  includes a recess  222  that is shaped to mimic the shape of gasket  214  such that when assembled, gasket  214  provides a generally smooth contour along the exterior surface of upper frame member  100  associated with pivot assembly  120 . 
     When assembled, pivot assembly  120  provides a secure connection between upper frame member  100  and seat tube  22  and does so in a manner that prevents lateral, longitudinal, and vertical movement of seat tube  22  relative to upper frame member  100  but allows rotation of seat tube  22  about axis  180  associated with opening  132  which is collinear with pivot assembly  120  relative to upper frame member  100 . Such a connection allows only flexion or flexing movement of seat tube  22  relative to the other structural members of bicycle frame assembly  12  during use of bicycle  10 . 
     As mentioned above, other interactions between seat tube  22  and frame assembly  12  are envisioned that allow similar deflection of the seat tube  22 . For instance, seat tube  22  could include a passage like passage  130  or otherwise be contoured so that the seat tube passed around the top tube/seat stays/lug and/or such that the top tube/seat stays/lug pass through the seat tube. Still another alternative includes connecting the seat stays to the upper frame member or top tube at a location forward of the seat tube such that the seat tube would be positioned in an area generally flanked by the seat stays. Referring to  FIG. 6 , although an axis, indicated by line  180 , of pivot assembly  120  is offset in an forward direction relative to the longitudinal axis  206  of seat tube  22 , is appreciated that axis  180  could be oriented to intersect axis  206  or offset in a rearward direction relative thereto so as to alter the deflection performance of seat tube  22  and/or to better suit the preferences of a given rider or class of users. 
     Referring to  FIG. 6 , during normal use of frame assembly  12 , seat tube  22  maintains a generally “at rest” configuration as represented by seat tube  22  shown in  FIG. 6 . Preferably, seat tube  22  has a fairly linear at rest orientation. Understandably, during normal use, some initial deflection of seat tube  22  may occur depending on the weight and preferred orientation of the rider during normal use over relatively smooth terrain. During an impact event, indicated by arrow  230 , a downward and rearward bending moment is imparted to seat tube  22  by the interaction of the rider with the rear portion of a saddle, which is commonly offset to the rear of the longitudinal centerline  206  of seat tube  22 . Such loading of the seat tube allows seat tube  22  to pivot in a passive manner about pivot assembly  120  and results in a rearward deflection of an upper portion  232  of seat tube  22  positioned above pivot assembly  120  and a forward deflection of a lower portion  234  of seat tube  22  that is positioned between pivot assembly  120  and bottom bracket  110  relative to the at-rest orientation. 
     The deflection of seat tube  22  relative to upper frame member  100  and lower frame member  101  is shown graphically in  FIG. 6  by line  236 . Such a configuration allows near the entirety of seat tube  22  to deflect from an at rest position to a “bent” orientation, represented by line  236  to improve the vertical compliance of frame assembly  12 . Supporting an upper end of seat tube  22  proximate the intersection of seat tube  22  with upper frame member  100  provides a fairly rigid feel of frame assembly  12  during all riding conditions but mitigates the communication of undampened travel surface discontinuities to the rider via rider interaction with the bicycle seat. Such performance improves rider comfort and decreases rider discomfort commonly associated with extended rides. Preferably, seat tube  22  deflects no more than 15 degrees from an at rest orientation and more preferably, seat tube  22  deflects no more than 7 degrees from a rest position in response to rider interaction with seat  16 . Such a configuration has been shown to provide a desired degree of responsiveness to rider interaction with the bicycle frame and does so in a manner that improves the vertical compliance of the bicycle frame assembly without unduly detracting from the same. However, it is appreciated that any desired range of deflection can be provided. Preferably, the greatest deflection value is associated with a deflection that a rider will tolerate and still feel comfortable on the bicycle during most riding conditions to a near unperceivable deflection during most riding conditions. 
     As shown in the experimental data below, frame assembly  12  provides greater longitudinal deflection of the seat tube with comparable lateral stiffness for bicycle frames having similar shapes and with nearly negligible contribution to the overall weight of the bicycle frame assembly. It is further envisioned that the forward and/or rearward orientation of the pivot axis relative to the longitudinal axis of the seat tube can be manipulated to satisfy a wide variety of rider performance preferences and/or to alter the deflection performance of the seat tube. It is further appreciated that the construction of the seat tube can be manipulated to further alter the vertical compliance of the frame assembly while providing a robust bicycle frame assembly. 
     
       
         
           
               
               
               
               
               
               
               
               
             
               
                   
               
               
                   
                   
                   
                   
                   
                 Head 
                   
                   
               
               
                   
                   
                   
                   
                 Full 
                 Tube 
               
               
                   
                   
                   
                   
                 Frame 
                 Stiffness 
                 BB 
               
               
                   
                   
                   
                   
                 Torsional 
                 N * m 
                 horizontal 
                 Vertical 
               
               
                   
                   
                 Frame 
                 Weight 
                 Stiffness 
                 per 
                 deflection 
                 Compliance 
               
               
                 Description 
                 Size 
                 Sample # 
                 (gram) 
                 (inches) 
                 degree 
                 (2) inches 
                 (inches) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 6SRS 
                 56 
                 2011- 
                 850 
                 0.1885 
                 78 
                 56 
                 0.86 
               
               
                 Baseline 
                 H3 
                 5428 
               
               
                 6SRS 
                 56 
                 2011- 
                 898 
                 0.186 
                  79* 
                 54 
                 1.38 
               
               
                 Pivot 
                 H3 
                 5697 
               
               
                   
               
            
           
         
       
     
     As shown in the data provided above, configuring a bicycle frame with the passive pivot connection between the seat tube and the upper frame member provides improved vertical compliance of the seat tube of approximately 60% with an increase in frame assembly weight of approximately 48 grams or only approximate 5% of the overall weight of the frame assembly. Accordingly, bicycle frame assembly  12  provides a bicycle frame have acceptable frame responsiveness with improved vertical compliance for improving rider comfort. 
     Therefore, one embodiment of the invention includes a bicycle frame assembly having a forward frame triangle that includes a top tube and a bottom tube. The top tube includes a first end that is connected to a head tube and a second end. The bottom tube includes a first end that is connected to the head tube and a second end. A bottom bracket is connected to the second end of the bottom tube. A seat tube extends in an upward direction from the bottom bracket. A pair of seat stays are connected to the top tube and extend in a rearward direction beyond the forward frame triangle. A pivot connects the seat tube to the forward frame triangle proximate the top tube at a location nearer a bicycle seat than the bottom bracket. 
     Another embodiment of the invention that includes one or more features combinable with the above embodiment includes a bicycle frame assembly having an upper frame member that includes a top tube and a pair of seat stays. The upper frame member extends between a dropout associated with a rear wheel and a head tube. An opening is formed in the upper frame member. A lower frame member that includes a bottom tube, a bottom bracket, and a chain stay extends between the dropout and the head tube. A seat tube extends from the lower frame member toward the upper frame member and passes through the opening in the upper frame member. A pivot connects the seat tube to the upper frame member proximate the opening so that more of the seat tube is located between the pivot and the bottom bracket than extends beyond the upper frame member. 
     Another embodiment of the invention that is useable with one or more of the aspects of the above embodiments discloses a method of allowing deflection of a seat tube. A seat tube is connected to a bottom bracket. The seat tube is connected to an upper frame member with a pivot that is located at an overlapping intersection of the seat tube and the upper frame member so that the seat tube can deflect from alignment along a line between the bottom bracket and the pivot. 
     The present invention has been described in terms of the preferred embodiment, and it is recognized that equivalents, alternatives, and modifications, aside from those expressly stated, are possible and within the scope of the appending claims.