Abstract:
An all-terrain vehicle (ATV) includes various storage compartments so that the weight loaded onto the vehicle may be evenly distributed between the front and rear suspension of the ATV. The ATV is capable of hauling a variety of loads over various terrains. The ATV contains a rear storage compartment, at least two side storage compartments, a front storage compartment, and a front rack to enable the rider to carry or attach a wide variety of loads onto the ATV without causing the vehicle to overturn or flip up due to the additional weight. Additionally, the ATV may also include a tree guard positioned on each side of the ATV to protect the rear storage and side compartments and to prevent cargo on the rear storage compartment from being dislodged by trees that might protrude into the rider&#39;s path.

Description:
[0001]    This is a continuation application of U.S. Non-Provisional application Ser. No. 09/950,926, filed on Sep. 13, 2001. This application also claims priority to Provisional Patent Application Serial No. 60/232,572 filed on Sep. 13, 2000, the content of which is hereby incorporated by reference in its entirety. This application is also related to patent application Ser. No. 09/057,652, entitled “ALL TERRAIN VEHICLE” filed on Apr. 9, 1998, the content of which is hereby incorporated by reference in its entirety and to patent application Ser. No. 09/339,517, entitled “STRADDLE-TYPE ALL TERRAIN VEHICLE WITH PROGRESSIVE DIFFERENTIAL” filed on Jun. 24, 1999, the content of which is hereby incorporated by reference in its entirety. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of Invention  
           [0003]    The present invention relates to the field of all terrain vehicles, and more particularly, the invention relates to a vehicle including storage compartments that are capable of hauling a variety of loads over various terrains.  
           [0004]    2. Description of Related Art  
           [0005]    During the last decade or so, the popularity of all terrain vehicles (also referred to as “ATV&#39;s”) has greatly increased. These types of vehicles are indeed very practical and versatile since they may be used for work or leisure related tasks. By virtue of their relatively compact nature, their great mobility and their traction, they are capable of maneuvering over all types of surfaces, from the common back yard to more challenging off-the-road terrain. Since ATVs are also fairly powerful, these vehicles may be used to pull or push various objects such as a trailer or a snowplow.  
           [0006]    [0006]FIG. 1 illustrates a saddle-type vehicle  2  conventionally found in the prior art. The vehicle  2  comprises four wheels  10  mounted to a frame  12 . The front wheels are steerable through a steering member  14  connected to a steering mechanism (not shown). The frame  12  comprises an upper member  12 ′ extending on an upper portion of the vehicle  2  above a power unit  20  and a lower member  12 ″ extending on a lower portion thereof. A fuel tank  16  and a seat  18  are disposed on an upper portion of the frame  12 . The power unit  20 , which represents one of the heaviest components of the vehicle, is typically mounted in a central portion of the vehicle, usually below the fuel tank  16  and at a front portion of the seat  18 . The vehicle  2  includes a rear storage rack  22  and a front storage rack  24 , both of which are supported by the frame  12 . However, the load capacities of the storage racks  22 ,  24  are limited. Furthermore, the shape and location of some storage racks, including the storage racks  22 ,  24  can adversely affect the vehicle&#39;s handling and stability.  
           [0007]    Another conventional four wheeled ATV is designed with a flat bed rear cargo support attached to the rear of the vehicle, above the rear wheels and behind the seat. However, this ATV has a tendency to overturn when loaded with heavy rear cargoes and/or is driven over uneven off-road terrain, because its design is incapable of compensating for the dynamic force created on the vehicle due to the load. It is believed that this inability to handle a heavy load is due, at least in part, to the fact that the wheel base of these vehicles is too short. Other factors that may contribute to the instability of this prior art vehicle relates to the poor weight distribution between the front and rear wheels, and the suspension design. One such prior art vehicle that is susceptible to overturning is the Prohauler, which is manufactured by Yamaha™. Moreover, while other ATVs may have greater load capacities, such as about 800 lbs., they generally require three sets of wheels to support such a load. Also, prior art ATVs require multiple steps to secure and unsecure the flat bed rear cargo support.  
           [0008]    Other vehicle designs are shown in U.S. Design Patent Nos. D445,066; D422,938; D439,549; D439,548; D427,109; D436,557; and D364,590. Each of these designs is capable of carrying a load in a rear bed, or box structure. These vehicles, however, are not considered to be true ATV&#39;s since they provide seating for a passenger, either with two separate seats (which are side by side) or with a long bench-style seat. Additionally, these vehicles share common characteristics, which are disadvantageous for purposes of operating as an ATV. In particular, the majority of these vehicles have a relatively low ground clearance, which prevents them from traversing rough terrain in true all-terrain conditions. However, those vehicles that are provided with a relatively high ground clearance also have a high center of gravity. The high ground clearance may allow for the traversal of rough terrain, but the high center of gravity makes these vehicles unstable while traversing this terrain.  
           [0009]    Furthermore, these vehicles have a decreased maneuvering capability, as compared to other ATV&#39;s. In particular, the turning radius is significantly increased. Additionally, the vehicles have a relatively wide stance due to their two person seating arrangement. The wide stance decreases the vehicle&#39;s ability to access some terrain features and makes it prone to hang-ups when traversing rough terrain, especially when coupled with a low ground clearance.  
           [0010]    Of course, these vehicles are able to carry relatively heavy loads, which makes them advantageous for certain applications. However, a high load capacity often is provided for by or necessitates an additional set of wheels at the rear of the vehicle. An extra set of wheels further decreases the vehicle&#39;s maneuverability and increases the overall weight of the vehicle. Additionally, when loaded, it has been found that the steerability of these vehicles is degraded due, at least in part, to the inability to appropriately distribute the load between the front and rear wheels of the vehicle.  
           [0011]    Another vehicle is disclosed in U.S. Pat. No. 5,076,387, which includes a storage receptacle that is integrally formed with a rear fender. The storage receptacle is formed as a recess within the rear fender. The recess extends below upper frame members of the frame of the vehicle. Additionally, the recess extends forwardly within the rear fender to a position beneath a seat of the vehicle. In this manner, the storage receptacle is not moveable, in particular pivotable, so as to facilitate removal of load therefrom.  
         SUMMARY OF THE INVENTION  
         [0012]    It is therefore an aspect of the invention to overcome the deficiencies noted above with respect to prior art ATVs, for example, by providing a four-wheeled ATV with a relatively high load capacity, while maintaining substantially all ATV functionality.  
           [0013]    It is another aspect to provide an ATV with a relatively high load capacity, while maintaining a high degree of maneuverability.  
           [0014]    It is another aspect to provide an ATV that has a high ground clearance and a low center of gravity when loaded.  
           [0015]    It is yet another aspect to provide an ATV that has a distribution of unloaded weight providing 50% of the weight of the vehicle on the front wheels and 50% of the weight on the rear wheels.  
           [0016]    It is another aspect to provide an ATV with a high load capacity that has four-wheel drive capability.  
           [0017]    It is yet another aspect to provide an ATV with a high load capacity that maintains steerability when loaded.  
           [0018]    It is another aspect to provide an ATV with a box bed situated at a rear portion thereof such that the bed is easily tilted by a user to dump a load from the box bed.  
           [0019]    It is another aspect to provide an ATV with a rear storage compartment having a high load capacity, without the tendency of the ATV to overturn when traversing over various terrain.  
           [0020]    Another aspect of the invention is to provide additional storage compartments formed on the fenders of the ATV. These additional storage compartments may be formed integrally with or attached to the fenders.  
           [0021]    A further aspect of the invention is to provide an ATV having a rear storage compartment that can be easily (un)secured and in which the load can be deposited a safe distance away from the rear of the ATV.  
           [0022]    Other aspects of the invention relate to providing a tree guard, preferably connected to the frame and/or the floorboards of the ATV, that can protect the rear storage compartment from damage caused by traveling close to trees. The tree guard may also provide a support for the additional side storage compartments that are integrally formed with or separately attached to the front and/or rear fenders of the ATV.  
           [0023]    In accordance with one embodiment of the invention a straddle-type vehicle is provided that includes a frame, a pair of front wheels suspended from a front portion of the frame, and a pair of rear wheels suspended from a rear portion of the frame and defining a rear axle. The vehicle also includes a power unit mounted on the frame and a rear storage compartment positioned over the rear portion of the frame. The rear storage compartment has a center of gravity positioned over the rear axle.  
           [0024]    In accordance with another embodiment of the invention provides a straddle-type vehicle including a frame, a pair of front wheels suspended from a front portion of the frame, and a pair of rear wheels suspended from a rear portion of the frame. The vehicle also includes a power unit mounted on the frame, a seat pivoted over the power unit, and a rear storage compartment positioned over the rear portion of the frame. The vehicle further includes a front storage rack and compartment positioned adjacent the front wheels and a side compartment on each side of the seat. Each of the side compartments is positioned between the front and rear wheels. The rear storage compartment, the front storage rack and compartment and the side compartment have a combined load capacity of about 800 lbs.  
           [0025]    Yet another embodiment of the invention provides a straddle-type vehicle including a frame, a pair of front wheels suspended from a front portion of the frame, and a pair of rear wheels suspended from a rear portion of the frame. The vehicle also includes a power unit mounted on the frame and at least one side compartment structure coupled to the frame on a lateral side of the frame between the pairs of front and rear wheels. The side compartment structure is configured to define a storage receptacle.  
           [0026]    Other aspects, objects and features of the invention will become apparent by reference to the following specification and to the drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0027]    The following is a description by way of preferred embodiments, reference being made to the following drawings, in which:  
         [0028]    [0028]FIG. 1 is a side view of saddle-type vehicle according to the prior art;  
         [0029]    [0029]FIG. 2 is a side view of an ATV according to one preferred embodiment of the present invention;  
         [0030]    [0030]FIG. 2A is a front view of the ATV shown in FIG. 2;  
         [0031]    [0031]FIG. 3 is a partial top perspective view from the left side of the ATV shown in FIG. 2, with the seat in the open position;  
         [0032]    [0032]FIG. 4 is a top plan view of the ATV shown in FIG. 2;  
         [0033]    [0033]FIG. 5 is a right side view of the ATV shown in FIG. 2, with the rear storage compartment in the open position;  
         [0034]    [0034]FIGS. 6 and 7 are schematic views illustrating a pivoting operation of the rear storage compartment;  
         [0035]    [0035]FIG. 8 is a side perspective view of a pivoting frame on which the rear storage compartment is mounted;  
         [0036]    [0036]FIG. 9 is a partial left side view of the pivoting frame shown in FIG. 8, which shows one of the compliant pins;  
         [0037]    [0037]FIG. 10 is a partial top perspective view of the ATV shown in FIG. 2, with the rear storage compartment in the open position;  
         [0038]    [0038]FIG. 11 is a schematic view illustrating the securing mechanism for securing the rear storage compartment to the frame of the ATV;  
         [0039]    [0039]FIG. 12 is a rear perspective view of the ATV shown in FIG. 2;  
         [0040]    [0040]FIG. 13 is a partial front perspective view of the ATV shown in FIG. 2 illustrating a side storage compartment;  
         [0041]    [0041]FIG. 14 is a detailed view of the right rear shock absorber according to the present invention;  
         [0042]    [0042]FIGS. 15 and 16 are detailed views of a cam mechanism according to the present invention in two different positions;  
         [0043]    [0043]FIG. 17 is a partial top view of the tree guard according to the present invention, with the side storage compartment being removed;  
         [0044]    [0044]FIG. 18 is a side view of the rear main frame used with the ATV shown in FIG. 2, in its unattached condition; and  
         [0045]    [0045]FIG. 19 is a top plan view of the rear main frame shown in FIG. 18. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0046]    A preferred embodiment of an ATV  100  according to the present invention is illustrated in FIG. 2. The ATV  100  includes a pair of front wheels  102  and a pair of rear wheels  104 . The front and rear wheels  102 ,  104  are suspended from a frame, which is more clearly visible in other Figures. The ATV  100  also includes a seat  106  that is pivotally mounted to the ATV  100 , as shown in FIG. 3, to allow access to a power unit, e.g., an engine. As shown in FIG. 3, a fixed pin  108  is mounted on a front main frame  110 F of the ATV  100 . The pin  108  is provided with an enlarged head portion that is received within a receiving orifice provided in the bottom of the seat  106 . A lever  112  can be activated in a known manner to force a retaining member within the orifice to release the seat  106 .  
         [0047]    Referring back to FIG. 2, the ATV  100  includes a front fender  114  over the front wheels  102  and a rear fender  116  over the rear wheels  104 . A front storage rack  190  and cover  192  are provided above the front fender  114 . A front storage compartment (not shown) is below the cover  192 . The front storage rack  190 , cover  192  and front storage compartment are described more fully in the U.S. patent application Ser. No. 09/057,652 cross-referenced above. Front and rear mudguards  118 ,  120 , respectively, extend downwardly from the front and rear fenders  114 ,  116 . A pair of handlebars  122  are provided to steer the front wheels  102 .  
         [0048]    The ATV  100  has a virtually unobstructed walk-through clearance area  140  located in front of the seat  107 . The clearance area  140  facilitates a rider&#39;s entrance on to and exit from the ATV  100 , as can be more easily seen in FIGS. 2 and 5. The clearance area  140  may also be used as additional storage area to permit the rider to position an item in a convenient area in front of the rider for easy and quick retrieval, such as snacks or other items, as described and illustrated (FIGS.  15 - 17 ) in the U.S. patent application Ser. No. 09/057,652 cross-referenced above. Further, as shown in FIG. 2A, the front portion of the ATV  100  also includes a bumper  160 , a front grille  175  and headlamps  185 . In addition, the cross-referenced U.S. patent application Ser. No. 09/057,652 includes a more complete description of other details and advantages of the clearance area, in addition to other general features of the ATV  100 . Although the present invention is described in reference to a step-through vehicle, the present invention may be utilized with other types of recreational vehicles.  
         [0049]    Further, as shown in FIG. 2, the ATV  100  includes a rear storage compartment  200  that is positioned above the rear wheels  104  and behind the seat  106 . The storage compartment  200  may be manufactured using a rotomolding process, which is known in the art. Although the rotomolding process can produce a storage compartment that is sturdy, strong, and durable, it is also possible to manufacture the storage compartment  200  using another process, such as injection molding. The rear storage compartment  200  includes a generally flat floor portion  202  (better visible in the top plan view of FIG. 4), side wall portions  204 , a front wall portion  206  and a rear wall portion  208 . The wall portions,  204 ,  206 ,  208  extend upwardly away from the floor portion  202  to define a compartment, as better shown in FIG. 4. The rear wall portion  208  may be pivotably connected to the bottom or side wall portions  202 ,  204 , like a tailgate. A pair of retaining members  209  (FIG. 12) hold the rear wall portion  208  in the upright position.  
         [0050]    It is also contemplated that the storage compartment  200  may be in the form of a substantially flat bed. For this embodiment (not shown), it is contemplated that the wall portions  204 - 208  may be significantly reduced in height, or eliminated altogether. Alternatively, one or more of the wall portions, for example, the front wall portion  206 , may remain, while other wall portions (e.g.,  204 ,  208 ) are eliminated.  
         [0051]    It is also contemplated that the wall portions  204 - 208  may be detachable from the flat floor portion  202 . In this manner, the rear storage compartment  200  may provide the box-type arrangement shown in FIG. 2, and be convertible into a flat bed arrangement. For this embodiment, it is contemplated that the wall portions  204 - 208  may be entirely removable, or may be pivotally connected at bottom edges thereof to the flat floor portion  202  so as to be pivoted from upright arrangements such as shown in FIG. 2 to either horizontally extending positions or depending positions relative to the flat floor portion  202 , such as shown in FIGS. 2A and 4. It is noted that it may be advantageous to provide a connection of the wall portions  204 - 208  such that the wall portions are pivotable into a horizontally extending position, such that a horizontal supporting surface is provided by the flat floor portion  202  and substantially flat upwardly facing surfaces  204 ′,  208 ′ of the wall portions  204 - 208 .  
         [0052]    As shown in FIG. 5, the rear storage compartment  200  is capable of pivoting from the closed position shown in FIG. 2 to an open or unloading position. The mechanism that allows for such pivoting will be discussed in relation to FIGS.  6 - 8 . FIGS. 6 and 7 are schematic views showing the rear storage compartment  200  attached to a pivoting frame  235 . FIG. 6 corresponds to the position of the rear storage compartment  200  shown in FIG. 2, and FIG. 7 corresponds to the position of the rear storage compartment  200  shown in FIG. 5. As shown in FIG. 8, the pivoting frame  235  includes longitudinal members  212  and links  213 . The pivoting frame  235  also includes front and rear cross supports  217 ,  219 . The longitudinal members  212  provide rigidity to the pivoting frame  235 . As shown in FIG. 5, the links  213  are coupled to a rear main frame  110 R.  
         [0053]    As cargo is being unloaded from the rear storage compartment  200 , the pivoting frame  235  pivots about the rear main frame  110 R such that the rear storage compartment  200  extends substantially outward from the rear of the ATV  100 . Thus, the cargo is unloaded at a safe distance (equal to the length of the links  213 ) rearwardly away from the rear of the ATV  100 . Further, an axis P about which the rear storage compartment pivots (relative to the rear main frame  110 R) is located between the front and rear walls  206 ,  208  of the rear storage compartment  200  relatively closer to the rear wall  208 . Accordingly, upon pivoting, the pivoting frame  235  pivots from the position shown in FIGS. 2 and 6 to the position shown FIGS. 5 and 7. Any portion of the load positioned rearwardly of the pivot axis P will not be added to the force required to raise the storage compartment  200 . In addition, this portion of the load to the rear of the storage compartment  200  will assist (by gravity) in lifting a portion of the load in the storage compartment that is forward of the pivot axis P. Accordingly, less effort is required to pivot the storage compartment  200 .  
         [0054]    It is also contemplated that in order to facilitate manual operation of the storage compartment  200 , a piston assembly  300  shown in FIG. 10, may be connected between the rear main frame  110 R and the pivoting frame  235 . The piston assembly  300  may be in the form of a hydraulic or pneumatic damper, such as a type suitable to slow movement of the storage compartment  200  relative to the main frame  110 R. It is also contemplated that the piston assembly  300  may be in the form of a hydraulic or pneumatic extension cylinder, such as a type suitable to apply a force on the pivoting frame  235  as the storage compartment  200  is pivoted to the open position, shown in FIG. 7. As shown in FIG. 10, the piston assembly  300  is disposed in a substantially horizontal position. The piston assembly  300  extends as the storage compartment  200  is pivoted into the open position and retracts as the storage compartment  200  is pivoted into the closed position.  
         [0055]    As shown in FIG. 9, the pivoting frame  235  also includes at least one compliant pin  242  that is attached to the cross support  217 . The compliant pin  242  is shown schematically in FIGS. 6 and 7, but it is not visible in FIG. 8 since it is hidden by the cross support  217 . The compliant pin  242  includes a pre-loaded spring  243  that surrounds a shaft  244  having a head in the form of a conical tapered tip  246 . A rubber bumper  249  is provided between the spring  243  and the tip  246 . The upper portion of the compliant pin  242  includes a bolt  251  for fastening the compliant pin  242  to the cross support member  217 .  
         [0056]    As illustrated in FIG. 10, the rear main frame  110 R includes a pair of pin receptacles  250 . Each receptacle  250  includes an aperture  252  and a reciprocating retaining member  254  (FIG. 11) in communication with the aperture  252 . A handle  240  (FIG. 10) is provided to reciprocate the retaining members  254  to selectively lock and unlock the rear storage compartment  200 . The handle  240  is connected to a first link  245  pivotably mounted to the rear main frame  110 R. The first link  245  is connected to a second link  241 , which is coupled with the retaining member  254  provided within each receptacle  250 . A spring  260  maintains the assembly in the position shown in FIG. 10. The handle  240  may be located on either side of the ATV in a location that is easily accessible for the rider. To disengage the retaining members  254  and thereby pivot the rear storage compartment  200 , the rider activates the handle  240 , which transfers the motion through the linkage assembly  241  to shift each of the retaining members  254  radially away from the aperture  252  so that the retaining member  254  releases the conical tip  246  of the complaint pin  242 . It is also contemplated that any other suitable handle structure can be used to reciprocate the retaining members  254 .  
         [0057]    Referring to FIG. 11, upon pivoting the storage compartment  200  into the horizontal position, gravity or manual movement of the compartment  200  urges the tip  246  past the retaining member  254 , at which point the retaining member  254  slides over the flat side  246 A of the tip  246 . The bumper  249  engages the receptacle  250  to serve as a cushion. (It is noted that bumpers  249  may also serve to attenuate vibration of the storage compartment  200 .) At this point, the rear storage compartment  200  is secured in the horizontal position. To release the tip  246  from the receptacle  250 , the rider need only move the handle  240  away from the rear main frame  110 R to move the retaining member  254  out of engagement with the tip  246 .  
         [0058]    If the tip  246  of the compliant pin  242  does not initially register with the aperture  252  in the receptacle  250 , the shaft  244  is designed to shift or tilt slightly so that the tip  246  will slide into the aperture  252 . If the tip  246  is misaligned and encounters the periphery of the aperture  252 , the shaft  244  will be forced upwardly against the force of the pre-loaded spring  243 . Upon compression of the spring  243 , the shaft  244  will tilt to achieve alignment with the aperture  252 , as shown in FIG. 11. Furthermore, the tip  246  of the shaft  244  is tapered or cone shaped to facilitate the insertion of the tip  246  into the aperture  252 . Once the tip  246  enters the aperture  252 , the spring  243  expands causing the shaft  244  to return to its original orientation, which is normal to the cross support  217 . It is noted that the springs  243  may also serve to attenuate vibration of the storage compartment  200 .  
         [0059]    Conventional four wheeled ATVs that have included a rear flat bed are prone to overturning, e.g., flipping up, when the ATV is driven through off-road terrain, especially if the vehicle was saddled with additional weight. However, the weight distribution, suspension and wheelbase of the ATV  100  in FIG. 2 reduces the likelihood of such mishaps, which will be discussed in detail below.  
         [0060]    In particular, as illustrated in FIG. 5, a length L of the wheel base has been increased compared to a conventional ATV. The wheel base extends longitudinally from imaginary axis x 1  to an imaginary axis x 2 , which axes are defined by the axles of the front and rear pairs of wheels. The wheel base has been extended to add stability to the ATV  100  so that it is more resistant to tipping over. The extended wheel base also helps to evenly distribute the load between the front and rear wheels. The ATV  100  has a 50/50 weight distribution over the front and rear wheels when unloaded. This provides a more stable platform for the rear storage compartment  200  so that the ATV can traverse uneven or off-road terrain. This is especially important when the ATV has been loaded with additional weight.  
         [0061]    It is contemplated that, in order to provide greater stability of the ATV  100 , the wheel base of the ATV may be extended by about 10 inches relative to a conventional ATV. Of course, the extension distance can be varied depending on the particular ATV application. In particular, the wheel base may be adjusted in order to correspondingly adjust the turning radius of the ATV. For example, the wheel base of the ATV  100  may be from 55 inches to 65 inches.  
         [0062]    Further, the center of gravity of the rear storage compartment  200  is positioned so that it is centered on a rear axle  141  of the ATV  100 , shown in FIG. 2. In FIG. 2, an arrow designates the center of gravity of the box bed  200 . The rear storage compartment  200  is positioned above a pair of rear shock absorbers  155 . The shock absorbers  155  are perpendicular to both the axle  141  and the bottom portion  202  of the rear storage compartment  200 . This overall architecture aids in evenly distributing the weight of the load and enables higher load capacity. Although the rear storage compartment  200  is described as having a substantially rectangular box shape, in keeping within the spirit of the invention, other configurations may be used.  
         [0063]    The location and distribution of the weight of the various storage compartments will now be discussed. Generally, FIG. 2 illustrates the vehicle according to the invention including various additional storage compartments that are strategically designed and positioned so that the weight of the load is advantageously distributed. The novel design of the ATV  100  also allows it to be adaptable to contain several additional storage compartments.  
         [0064]    For example, a side compartment  225  may be provided on each lateral portion of the ATV  100 . In one contemplated embodiment, shown in FIG. 13, each side compartment  225  may be formed integrally with respective rear fenders  116  for storage of additional materials within storage receptacles provided by the side compartments  225 . As shown, the side compartments  225  are defined by a laterally outwardly facing wall portion  225 A, spaced from a engine enclosure  226 ; a forwardly facing wall portion  225 B, which is connected to and extends outwardly from the engine enclosure  226 ; a laterally facing wall portion  226 C, which is provided by a portion of the engine enclosure  226 ; and a rearward wall portion which is provided by the rear fender structure  116 . Additionally, the wall portion  225 A may form a lip portion  225 E that extends along the fender structure  116 .  
         [0065]    It is contemplated that the side compartments  225  may alternatively be formed integrally with the front fender  114  in a similar manner. It may also be possible to provide the side compartments  225  formed integrally with the rear fender  116 , while an additional pair of side compartments (not shown) are formed integrally with the front fender  114 .  
         [0066]    Alternatively, instead of being integrally formed with the front or rear fenders  114 ,  116 , the side compartments  225  may be manufactured so that they are detachably mounted to the front or rear fenders  114 ,  116  or the frame  11 F. It is contemplated that the arrangement for detachably mounting the side compartments  225  may include, for example, Velcro™, a pin-and-groove arrangement, or another similar attachment mechanism. In this manner, the side compartments  225 , could be removed and used as portable storage containers. It is also contemplated that the side compartments  225  may be provided with lids or covers. For example, cover members may be provided that are removable from the side compartments  225  or are pivotally connected to the side compartments  225  so as to be pivoted open or closed.  
         [0067]    The placement of loads within the side compartments  225  facilitates an even distribution of load on the ATV  100 . The location of the side compartments  225  may be altered to correspondingly alter the distribution of load. For example, the side compartments  225  may be positioned at a relatively forward position to add weight to the forward portion of the ATV  100  (and vice-versa). Additionally, the side compartments  225  are preferably positioned relatively low on the ATV  100 . In this manner, load may be placed within the side compartments  225  and thereby lower the center of gravity without compromising ground clearance of the ATV  100 . This arrangement increases the stability of the ATV  100 . Of the side compartments  225  may be positioned anywhere between the front and rear wheels  102 ,  104 .  
         [0068]    The additional storage compartments of the ATV  100  greatly increase the storage and load capacity of the vehicle. The location and the shape of the compartments are designed so that the weight of the cargo is strategically distributed. As discussed previously, the ATV  100  is arranged such that, when unloaded, there is a distribution of weight of the vehicle including approximately 50% of the weight on the front wheels 102 and approximately 50% of the weight on the rear wheels  104 . The specific location and shape of the front rack  190 , side compartments  225 , and the rear compartment  200  (as well as the componetry of the ATV  100  itself) makes it possible to evenly distribute load over the vehicle to generally maintain the 50/50 weight distribution over the front and rear wheels  102 ,  104 . The following is an example of a relatively evenly distributed load totaling 440 lbs. with five elements: a first element of 90 lbs. (approximately 20% of the total load) is positioned on the front rack; a second element of 20 lbs. (approximately 4.5% of the total load) is disposed within the fuel tank as fuel; and operator provides a third element of 200 lbs. (approximately 45% of the total load) and is situated on the seat  106 ; a fourth element of 30 lbs. (approximately 7% of the total load) is split between right and left side compartments  225 ; and a fifth element of 100 lbs. (approximately 23% of the total load) is situated within the rear storage compartment  200 . Of course, other load distributions and placement of elements are possible.  
         [0069]    Another embodiment of the invention relates to the shock absorber  155  shown in FIG. 12. One end of each shock absorber  155  is connected to the rear axle  140  and the other end is connected to the rear main frame  110 R of the ATV  100 . Alternatively, a single shock absorber  155  could be used at the rear, provided that it is located in a generally central location. As shown in FIG. 12, each shock absorber  155  is substantially perpendicular to the axle  141 . Each shock absorber  155  is also perpendicular to the bottom portion  202  of the rear storage compartment  200 , as described.  
         [0070]    As shown in FIG. 14, each shock absorber  155  includes a spring having a top portion  155   a  and a bottom portion  155   b . The top portion  155   a  has loosely wound coils and the bottom portion  155   b  of each spring has tightly wound coils. During light loading or traveling on relatively smooth terrain, minor shocks are absorbed substantially by the loosely wound top coils  155   a  only. During heavy loading or traveling on rough terrain, heavy bumps are absorbed by both the top and bottom portions  155   a ,  155   b . The spring is sometimes referred to as a dual-rate spring.  
         [0071]    As shown in FIGS. 15 and 16, an adjustable cam  170  is mounted to a lower portion of each of the shock absorbers  155 . In FIG. 15, the cam  170  is positioned to provide a relatively soft ride. In FIG. 16, the cam  170  has been rotated to compress the spring to provide a relatively firmer ride. In FIG. 16, the spacing between the coils has been decreased. The rotation of the cam  170  adjusts the tautness of the dual-rate springs, which in turn adjusts the ride of the rear suspension.  
         [0072]    Full foot rests  210  (FIGS. 2, 4 and  17 ) are also provided on each side of the ATV  100 , between the front and rear mudguards  118 ,  120 . The full foot rests  210  provide increased comfort in contrast with the typical foot peg since the rider&#39;s weight is distributed over the entire bottom surface of the foot.  
         [0073]    The ATV  100  also has a tree guard  262  depicted in FIGS. 2, 5 and  17 . With typical ATV vehicles, as they travel through densely populated forest, trees could knock the cargo off the vehicle or strike the rear storage compartment  200  or side compartments  225 . However, the tree guard  262  protects the rear storage compartment  200  and its cargo, as well as the side compartments  225  and the rear fenders and mudguards. The tree guards  262  can be connected to a lower frame portion  110 L and may be formed integrally with the foot rests as shown in FIG. 17. The width of the tree guard  262  is at least equal to and preferably slightly wider than a width of the rear storage compartment  200 . The tree guard  262  may be constructed from tubular or stamped members. Thus, as the vehicle travels through a forest or wooded area, the tree guards  262  impace the tree instead of the storage compartments  200  or  225 . A portion  264  of the tree guard  262  may provide support for the side compartment  225 .  
         [0074]    It is contemplated that the overall frame of the ATV  100  may be unitary. However, another feature of the invention is that the overall frame of the ATV  100  frame may be split into the front main frame  110 F (FIG. 3) and the rear main frame  110 R. FIGS. 18 and 19 illustrate side and top plan views of the rear main frame  110 R. The rear main frame  110 R includes a fixed pivot point  157  about which the pivoting frame  235  (FIGS.  5 - 8 ) pivots. A plurality of connection points  161  are provided at the forward end of the rear main frame  110 R. The connection points  161  connect to the front main frame  110 F (FIG. 3). As shown in FIG. 19, a mounting plate  165  is provided for each receptacle  250  (FIG. 10). A mounting point  159  (FIGS. 14 and 18) provides an attachment point for the upper end of the shock absorber  155 . The front main frame  110 F includes an attachment point for each of the front shock absorbers. The connection points  161  between the front main frame  110 F and the rear main frame  110 R may be designed to intentionally break if a load exerted between the frame portions exceeds a predetermined limit. Stated differently, the joint may be provided with a mechanical “fuse”. The joint breaks before the load causes any damage to either the front main frame  110 F or the rear main frame  110 R. One advantage to the split frame design is that if one portion of the frame suffers any structural damage it can be easily replaced or repaired without having to replace the undamaged portion of the frame.  
         [0075]    As described, the front shock absorbers are attached to the front main frame  110 F and the rear shock absorbers are attached to the rear main frame  110 R. In contrast, the prior art vehicles typically attach the front and rear shock absorbers to a unitary main frame. Because the front main frame  110 F and the rear main frame  110 R are split, one of the frame members, e.g., the rear main frame  110 R, can be replaced with another frame portion that has a different design or utility. For example, the rear main frame  110 R, which pivotably supports the rear storage compartment  200 , can be replaced with a different rear frame that is suitable for example the ATV described in the application cross-referenced above. Consequently, because the front main frame  110 F does not change for most ATVs, the overall costs of the ATVs can be reduced since the same front main frame can be massed produced for use on a wide variety of ATVs. Moreover, the interchangeability of the frame parts permits the ATV to be easily fitted with new upgrades because only the newly-modified portion of the frame has to be changed out when new features are added or modifications are made to the vehicle. The front and rear main frames of the split-frame may be made of conventional construction and may be constructed from tubular or stamped members.  
         [0076]    Furthermore, it is contemplated that the ATV  100  may be provided with four-wheel drive capability. For example, the ATV  100  may include a progressive differential of the type disclosed in co-pending U.S. application Ser. No. 09/339,517, which has been incorporated by reference in its entirety. A progressive differential of this type may be used in the rear of the ATV coupled to the rear wheels  104  and/or may be used in the front of the ATV  100  coupled to the front wheels  102 . The progressive differential provides the four-wheel drive capability of the ATV  100 . The four-wheel drive capability may be advantageous for load carrying, and especially load carrying while traversing relatively rough terrain.  
         [0077]    The above description of a preferred embodiment should not be interpreted in any limiting manner since variations and refinements are possible which are within the spirit and scope of the present invention.