The present disclosure, in general, relates to the field of vehicles. Particularly, but not exclusively, the present disclosure relates to suspension systems for two-wheeled vehicles. Further, embodiments of the present disclosure relate to a rear suspension system for a two-wheeled vehicle.
BACKGROUND OF THE DISCLOSURE
[002] Conventionally, two-wheeled vehicles such as, but not limited to, motorcycles are provided with suspension systems for improved handling and braking performance. Suspension systems also enhance passenger safety and ride-comfort by insulating passengers from bumps, and vibrations. Motorcycles are generally provided with a pair of telescopic fork tubes for front suspension system and a swingarm with at least one shock absorber for rear suspension system. On road two-wheelers are provided with two shock absorbers (also referred to as twin shock-absorbers) for rear suspension system. Commonly, a damper (such as a hydraulic piston type damper) including a coil spring (also known as compression spring) is employed as shock absorber in rear suspension systems. The swingarm of the rear suspension system is coupled to the rear axle of the vehicle. That is, the swingarm and the rear axle are connected such that the rear axle is free to move up and down (relative to ground), to enable a rear wheel of the vehicle to maneuver bumps and potholes in the road. The rear suspension system including the shock absorbers is configured to dampen shock impulse and dissipate kinetic energy resulting therefrom.
[003] Rear suspension systems of motorcycles, that include shock absorbers, are configured by taking into consideration parameters such as, but not limited to, weight of the vehicle, average weight range of the passengers, average load range to which the vehicle is subjected, and typical driving speed ranges of the vehicle. A damping coefficient of the shock absorber and a spring constant (also referred to as spring rate) of the coil spring is often fixed and is configured during assembly of

the suspension system. Configuring the coil spring to be stiff with higher spring constant enables quick restoration of the coil spring to initial state (subsequent to deflection of the coil spring). On the contrary, configuring the coil spring to be less stiff with a lower spring constant enables higher absorption of energy, in comparison with a stiffer spring. However, a major drawback associated with such rear suspension systems (i.e., systems that have coil springs with fixed spring constant) is that the coil spring is only configured to handle a limited range of road conditions and weight conditions. Accordingly, usage of vehicles in terrains and load ranges beyond such limited range, makes ride uncomfortable for the passengers and negatively affects fuel efficiency and performance of the vehicle.
[004] Drawbacks associated with above-described rear suspension systems are overcome by having a combination of two coil springs where one spring is positioned inside the other in a co-axial manner. However, usage of two springs increases costs associated with rear suspension systems and further requires re-design and re-configuration of the entire rear suspension system for accommodating two springs. Further, usage of two springs increases number of moving parts and associated wear and tear, whereby requiring frequent maintenance and regular servicing of the suspension system.
[005] The present disclosure is directed to overcome one or more limitations stated above or any other limitations associated with the conventional configuration of the rear suspension systems used in two-wheelers.
SUMMARY OF THE DISCLOSURE
[006] One or more shortcomings of the prior art are overcome by a rear suspension system for a two-wheeled vehicle as claimed and additional advantages are provided through the rear suspension system as claimed in the present disclosure. Additional features and advantages are realized through the techniques of the present disclosure. Other embodiments and aspects of the disclosure are described in detail herein and are considered a part of the claimed disclosure.

[007] In one non-limiting embodiment of the present disclosure, a rear suspension system for a two-wheeled vehicle is disclosed. The system includes a first suspension device positioned between a wheel and a body frame of the vehicle. The first suspension device includes a first compression spring. Further, a second suspension device is positioned between the wheel and the body frame of the vehicle. The second suspension device includes a second compression spring. The first compression spring and the second compression spring are configured with different spring rates. In comparison with the conventional spring system having only one changeover point, the system provides two changeover points for the same number of springs.
[008] In an embodiment of the present disclosure, at least one of the first compression spring and the second compression spring includes a first portion defined with first pitch and a second portion defined with second pitch. A length of the first portion and the second portion of the first compression spring is different from a length of the first portion and the second portion of the second compression spring. Such configuration of the first compression spring and the second compression spring enables achieving more than one spring rate in each spring, when subjected to different load conditions.
[009] In an embodiment of the present disclosure, a position of the first portion and the second portion of the first compression spring is different from a position of the first portion and the second portion of the second compression spring. Such configuration of the first compression spring and the second compression spring enables achieving more than one spring rate in each spring, when subjected to different load conditions.
[010] In an embodiment of the present disclosure, the second suspension device is configured parallel to the first suspension device. Such configuration of the system enables employing the system in two-wheeled vehicles such as, but not limited to, motorcycles.

[Oil] In an embodiment of the present disclosure, at least one of the first suspension device and the second suspension device includes a damping unit. The damping unit includes a cylinder and a piston moveable within the cylinder. The first compression spring is positioned coaxially with the cylinder of the damping unit of the first suspension device. Further, the second compression spring is positioned coaxially with the cylinder of the damping unit of the second suspension device. Such configuration of the system enables employing the damping units in rear suspension systems of two-wheeled vehicles such as, but not limited to, motorcycles.
[012] In an embodiment of the present disclosure, the first compression spring has a first spring rate for a first range of load and a second spring rate for a second range of load. Such configuration of the first compression spring enables achieving more than one spring rate in the first compression spring, when subjected to different load conditions.
[013] In an embodiment of the present disclosure, the second compression spring has a first spring rate for the first range of load and a second spring rate for the second range of load. Such configuration of the second compression spring enables achieving more than one spring rate in the second compression spring, when subjected to different load conditions.
[014] In an embodiment of the present disclosure, magnitude of the second range of load is greater than magnitude of the first range of load. Such configuration of the system enables employment of the system under different load conditions.
[015] In an embodiment of the present disclosure, magnitude of the second spring rate is greater than magnitude of the first spring rate. Such configuration of the system enables employment of the system under different load conditions and operational requirements.
[016] In an embodiment of the present disclosure, spring rate of the first compression spring and the second compression spring is dependent on length and

position of the first portion and the second portion of each of the first compression spring and the second compression spring, respectively. Such configuration of the system enables achieving different spring rates (which is progressive) under different load conditions.
[017] In an embodiment of the present disclosure, the system is configured to have a progressive spring rate with a plurality of changeover points. The progressive spring rate and the plurality of changeover points are dependent on spring rate of the first compression spring and the second compression spring. Such configuration of the system enables employment of the system under different load conditions and operational requirements.
[018] In an embodiment of the present disclosure, the progressive spring rate is dependent on magnitude of load acting on each of the first compression spring and the second compression spring. The system is configured to exhibit a progressive spring rate and suspension characteristics, whereby increasing ride comfort for the passengers.
[019] In an embodiment of the present disclosure, the progressive spring rate is varied by varying the first pitch and the second pitch of each of the first compression spring and the second compression spring, respectively. Such configuration of the system makes the system suitable for handling a wide range of road conditions and weight conditions, whereby catering to extensive operational requirements of the vehicle.
[020] In one non-limiting embodiment of the present disclosure, a two-wheeled vehicle is disclosed. The two-wheeled vehicle includes a body frame having a front fork, a head tube, a down tube and a pair of seat rails. A seating assembly is coupled to the pair of seat rails and mounted on the body frame. Further, a steering handlebar is pivotally coupled to the head tube. A front wheel and a rear wheel are rotatably coupled to the body frame. The two-wheeled vehicle also includes a rear suspension system. The rear-suspension system includes a first suspension device positioned

between a wheel and the body frame of the vehicle. The first suspension device includes a first compression spring. Further, a second suspension device is positioned between the wheel and the body frame of the vehicle. The second suspension device includes a second compression spring. The first compression spring and the second compression spring are configured with different spring rates. The system of the two-wheeled vehicle is configured to exhibit progressive spring rate with a plurality of changeover points, which makes the suspension characteristic of the system dynamic and adaptable to instant road conditions.
[021] The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
[022] The novel features and characteristics of the disclosure are set forth in the appended claims. The disclosure itself, however, as well as a preferred mode of use, further objectives, and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying figures. One or more embodiments are now described, by way of example only, with reference to the accompanying figures wherein like reference numerals represent like elements and in which:
[023] Figure 1 illustrates a schematic side view of a vehicle including a rear suspension system, in accordance with an embodiment of the present disclosure.
[024] Figure 2 illustrates another schematic side view of the vehicle of Figure 1;
[025] Figure 3 a illustrates a first suspension device of the rear suspension system, in accordance with an embodiment of the present disclosure;
[026] Figure 3b illustrate a second suspension device of the rear suspension system, in accordance with an embodiment of the present disclosure;

[027] Figure 4a illustrates a first compression spring of the first suspension device of Figure 3 a;
[028] Figure 4b illustrates a second compression spring of the second suspension device of Figure 3b;
[029] Figure 5 illustrates a graph of suspension characteristics for a conventional rear suspension system of a vehicle;
[030] Figure 6 illustrates a graph of suspension characteristics for the rear suspension system, in accordance with an embodiment of the present disclosure;
[031] Figure 7 illustrates a graph of wheel rate of the vehicle comprising the rear suspension system, in accordance with an embodiment of the present disclosure;
[032] The figures depict embodiments of the disclosure for purposes of illustration only. One skilled in the art will readily recognize from the following description that alternative embodiments of the apparatus illustrated herein may be employed without departing from the principles of the disclosure described herein.
DETAILED DESCRIPTION
[033] While the embodiments in the disclosure are subject to various modifications and alternative forms, specific embodiments thereof have been shown by the way of example in the figures and will be described below. It should be understood, however that it is not intended to limit the disclosure to the particular forms disclosed, but on the contrary, the disclosure is to cover all modifications, equivalents, and alternative falling within the scope of the disclosure.
[034] Before describing detailed embodiments, it may be observed that the novelty and inventive step that are in accordance with the present disclosure resides in a rear suspension system for a two-wheeled vehicle. It is to be noted that a person skilled in the art can be motivated from the present disclosure and modify the

various constructions of the rear suspension system, and the two-wheeled vehicle including the rear suspension system. However, such modification should be construed within the scope of the present disclosure. Accordingly, the drawings are showing only those specific details that are pertinent to understanding the embodiments of the present disclosure so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having benefit of the description herein.
[035] In the present disclosure, the term "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any embodiment or implementation of the present subject matter described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments.
[036] The terms "comprises", "comprising", or any other variations thereof used in the disclosure, are intended to cover non-exclusive inclusions, such that an apparatus, device, assembly, mechanism, system, and method that comprises a list of components does not include only those components but may include other components not expressly listed or inherent to such apparatus, system, assembly, or device. In other words, one or more elements in a system proceeded by "comprises... a" does not, without more constraints, preclude the existence of other elements or additional elements in the system or apparatus or method.
[037] The terms like "at least one" and "one or more" may be used interchangeably or in combination throughout the description.
[038] While the present disclosure is illustrated in the context of a two-wheeled vehicle, however, the rear suspension system and aspects and features thereof can be used with other type of vehicles as well. The terms "modular vehicle", "vehicle", "two-wheeled vehicle", "electric vehicle", "EV" and "motorcycle" have been interchangeably used throughout the description. The term "vehicle" comprises vehicles such as motorcycles, scooters, bicycles, mopeds, scooter type vehicle, and the like.

[039] The terms "front/forward", "rear/rearward/back/backward",
"up/upper/top", "down/lower/lower ward/downward, bottom", "left/leftward", "right/rightward" used therein represents the directions as seen from a vehicle driver sitting astride.
[040] Reference will now be made to the exemplary embodiments of the disclosure, as illustrated in the accompanying drawings. Wherever possible, same numerals will be used to refer to the same or like parts. Embodiments of the disclosure are described in the following paragraphs with reference to FIGS. 1 to 7. In FIGS. 1 to 7, the same element or elements which have same functions are indicated by the same reference signs.
[041] Embodiments of the present disclosure disclose a rear suspension system (also referred to as the 'system' hereinafter) for a two-wheeled vehicle. The system includes a first suspension device positioned between a wheel and a body frame of the vehicle. The first suspension device includes a first compression spring. Further, a second suspension device is positioned between the wheel and the body frame of the vehicle. The second suspension device includes a second compression spring. The first compression spring and the second compression spring are configured with different spring rates.
[042] In an embodiment, the term ' spring' or 'coil spring' or 'compression spring' as used herein refers to a resilient member employed in rear suspension systems of two-wheeled vehicles. Although the rear suspension system of the present disclosure is described in the context of a two-wheeler vehicle and in context of a motorcycle, such description is not intended to limit the disclosure to the particular forms disclosed, but on the contrary, the disclosure is to cover all modifications, equivalents, and alternative falling within the scope of the disclosure. Accordingly, it is to be understood by a person skilled in the art that the system of the present disclosure may be employed in other vehicle, device, apparatus, and machine, that

has similar suspension requirements and that which requires similar suspension characteristics.
[043] The disclosure is described in the following paragraphs with reference to Figures 1 to 7. In the figures, the same element or elements which have same functions are indicated by the same reference signs. It is to be noted that, the entire set up of the system including mounting or coupling arrangements used for mounting/coupling of the system to the body frame of the vehicles is not illustrated in the figures for the purpose of simplicity. One skilled in the art would appreciate that the system as disclosed in the present disclosure may be used with more than two damping units and with more than one spring in each damping unit comprised in the rear suspension system.
[044] Figures 1 and 2 illustrate a two-wheeled vehicle (100) (also referred to in as the 'vehicle' hereinafter) in accordance with an embodiment of the present disclosure. The vehicle (100) referred to herein, embodies a motorcycle. However, the vehicle (100) may include any other two-wheeled vehicle such as, but not limited to, scooters, mopeds, and the like. The vehicle (100) may also include vehicles such as three-wheeled vehicle, all-terrain vehicles (ATV) and the like, without limiting scope of the present disclosure. Figure 1 illustrates a schematic first side view of the vehicle (100) such as a motorcycle, of conventional construction. Figure 2 illustrates a schematic second side view of the vehicle (100). The first side view depicted in Figure 1 may be a right-side view of the vehicle (100), when the vehicle (100) is viewed from a front direction, depicted by pointer A in Figure 1. Further, the second side view depicted in Figure 2 may be a left-side view of the vehicle (100), when the vehicle (100) is viewed from the front direction, depicted by pointer A in Figure 1.
[045] As illustrated in Figures 1 and 2, the vehicle (100) of the present disclosure comprises one or more body parts, such as a body frame (101), a front fork (2), a steering handle bar (3) (also called as handlebar), a front wheel (4), a seat (5), a swing arm (6), a tail light (7), a rear wheel (8), a front fender (9), a rear fender (10),

a headlight (11), an engine (12), a fuel tank (13), a rear grip (14), a rear suspension system (15), a saree guard (16), a rider step (17), a pillion step (18), a stand device (20) and a stand spring (19). The front wheel (4) and the rear wheel (8) may be rotatably coupled to the body frame (101). It may be noted that the vehicle (100) as depicted in Figures 1 and 2 includes above stated parts, however, those ordinarily skilled in the art would appreciate that the vehicle (100) may include other parts such as, a down tube, a pair of seat rails to mount the seat (5) or a seating assembly (5), battery, torque rod, rear view mirrors and the like, without limiting the scope of the present disclosure.
[046] The present disclosure relates to the rear suspension system (15) of the vehicle (100). The rear suspension system (15) of the vehicle (100) may include two suspension devices (21 (visible in Figure 1) and 22 (visible in Figure 2)) mounted parallel to each other. However, the two suspension devices (21 and 22) may also be mounted such that the two suspension devices (21 and 22) are not parallel to each other. Such mounting may depend on type of suspension system and springs employed in such suspension system. Springs employed in such suspension system may be mounted either parallel or non-parallel to each other. However, as Figures 1 and 2 illustrate the first side view and the second side view of the vehicle (100), only one of the two suspension devices (21 and 22) is visible in the Figures 1 and 2. Accordingly, it is to be understood by those ordinarily skilled in the art, that the rear suspension system (15) of the vehicle (100) includes two suspension devices (21 and 22) that are mounted parallel to each other, with a first suspension device (21) mounted on the right-side of the vehicle (100) and a second suspension device (22) mounted on the left-side of the vehicle (100). Alternatively, it is also to be understood that the first suspension device (21) may be mounted on the left-side of the vehicle (100) and the second suspension device (22) may be mounted on the right-side of the vehicle (100). The first and the second suspension devices (21 and 22) may be coupled to at least one of the body frame (101), the swing arm (6) and to a rear axle (not shown in Figures) of the rear wheel (8) such that the rear axle of the rear wheel (8) is free to move up and down (relative to

ground), whereby enabling the rear wheel (8) of the vehicle (100) to maneuver bumps and potholes in the road. The first suspension device (21) and the second suspension device (22) may be mounted with a distance therebetween, where such distance is the space/volume within which at least a portion of the rear wheel (8), the swing arm (6) of the vehicle (100) is accommodated.
[047] The rear suspension system (15) (also referred to as the ' system' hereinafter) of the present disclosure is described with reference to Figures 1 to 7. The system (15) includes the first suspension device (21) and the second suspension device (22). Figures 3a and 3b illustrate the first suspension device (21) and the second suspension device (22) of the system (15). The first suspension device (21) may be positioned between the rear wheel (8) and the body frame (101) of the vehicle (100). Further, the second suspension device (22) is positioned between the rear wheel (8) and the body frame (101) of the vehicle (100), whereas on the opposite side of the vehicle (100). That is, the first suspension device (21) may be mounted on the right-side of the vehicle (100) and the second suspension device (22) may be mounted on the left-side of the vehicle (100). Alternatively, the first suspension device (21) may be mounted on the left-side of the vehicle (100) and the second suspension device (22) may be mounted on the right-side of the vehicle (100). The second suspension device (22) may be positioned parallel to the first suspension device (21) with an interval therebetween. The first suspension device (21) may include a first compression spring (23), while the second suspension device (22) may include a second compression spring (24).
[048] Figures 4a and 4b illustrate the first compression spring (23) and the second compression spring (24), in accordance with an embodiment of the present disclosure. The first compression spring (23) and the second compression spring (24) are configured with different spring rates.
[049] In an embodiment, each of the first suspension device (21) and the second suspension device (22) includes a damping unit (25a, 25b). The first suspension device (21) includes a first damping unit (25a). The second suspension device (22)

includes a second damping unit (25b). Each of the damping unit (25a, 25b) includes a cylinder and a piston moveable within the cylinder. The first damping unit (25a) includes a first cylinder (26a) and a first piston (27a) moveable within the first cylinder (26a). The first compression spring (23) is positioned coaxially with at least one of the first cylinder (26a) and the first piston (27a) of the first damping unit (25a). The second damping unit (25b) includes a second cylinder (26b) and a second piston (27b) moveable within the second cylinder (26b). The second compression spring (24) is positioned coaxially with at least one of the second cylinder (26b) and the second piston (27b) of the second damping unit (25b).
[050] In an embodiment, each of the first compression spring (23) and the second compression spring (24) includes a first portion (28a, 28b) defined with first pitch and a second portion (29a, 29b) defined with second pitch. As illustrated in the Figure 4a, the first compression spring (23) includes a first portion (28a) defined with first pitch and a second portion (29a) defined with second pitch. Similarly, the second compression spring (24) includes a first portion (28b) defined with first pitch and a second portion (29b) defined with second pitch. The term 'pitch' as used herein refers to distance from center of one coil to the center of an adjacent coil of the spring. That is, the pitch of the spring is measured from wire centre to wire centre of two adjacent coils of the spring. The pitch of the spring is measured parallel to a length axis of the spring.
[051] In an embodiment of the first compression spring (23), the first pitch of the first portion (28a) may be different from the second pitch of the second portion (29a). Similarly, in an embodiment of the second compression spring (24), the first pitch of the first portion (28b) may be different from the second pitch of the second portion (29b). Further, the first pitch of the first portion (28a) of the first compression spring (23) may be different from the first pitch of the first portion (28b) of the second compression spring (24). Likewise, the second pitch of the second portion (29b) of the second compression spring (24) may be different from the second pitch of the second portion (29a) of the first compression spring (23). However, in an embodiment, the first pitch of the first portion (28a) of the first

compression spring (23) may be similar or substantially equal to the second pitch of the second portion (29b) of the second compression spring (24). Correspondingly, the second pitch of the second portion (29a) of the first compression spring (23) may be similar or substantially equal to the first pitch of the first portion (28b) of the second compression spring (24). In such embodiment, the spring rate of the first compression spring (23) and the second compression spring (24) may be varied by varying material, wire diameter and number of coils comprised in each portion of the springs (23 and 24).
[052] In an embodiment, the first pitch and the second pitch of each of the first compression spring (23) and the second compression spring (24) is configured based on operational requirements of the vehicle (100) and may be based on parameters such as, but not limited to, weight of the vehicle (100), average weight range of the passengers, average load range to which the vehicle (100) is subjected, and typical driving speed ranges of the vehicle (100).
[053] In an embodiment, a length of the first portion (28a) and the second portion (29a) of the first compression spring (23) may be different from a length of the first portion (28b) and the second portion (29b) of the second compression spring (24). In a total length of the first compression spring (23), length of the first portion (28a) and the second portion (29a) may be configured in a ratio of 30:70. However, the length of the first portion (28a) and the second portion (29a) may also be configured in a ratio of 20:80, 40:60, 50:50 and the like. Correspondingly, in a total length of the second compression spring (24), length of the first portion (28b) and the second portion (29b) may be configured in a ratio of 30:70. However, the length of the first portion (28b) and the second portion (29b) may also be configured in a ratio of 20:80, 40:60, 50:50 and the like.
[054] In an embodiment, a position of the first portion (28a) and the second portion (29a) of the first compression spring (23) may be different from a position of the first portion (28b) and the second portion (29b) of the second compression spring (24). The first portion (28a) and the second portion (29a) of the first

compression spring (23) may be positioned such that the first portion (28a) and the second portion (29a) corresponds to a top portion and a bottom portion of the first compression spring (23). Alternatively, the first portion (28a) and the second portion (29a) of the first compression spring (23) may be positioned to correspond to the bottom portion and the top portion of the first compression spring (23). Further, the first portion (28b) and the second portion (29b) of the second compression spring (24) may be positioned such that the first portion (28b) and the second portion (29b) corresponds to a top portion and a bottom portion of the second compression spring (23). Alternatively, the first portion (28b) and the second portion (29b) of the second compression spring (24) may be positioned as the bottom portion and the top portion of the second compression spring (23).
[055] In an embodiment, by virtue of above-described configuration of the springs (23 and 24), the first portion (28a) and the second portion (29a) of the first compression spring (23) may have a first spring rate (kia) and a second spring rate (kib), respectively. The term 'spring rate' (also referred to as spring constant) as used herein refers to magnitude of force required to compress the spring by unit length. Further, the first portion (28b) and the second portion (29b) of the second compression spring (24) may have a first spring rate (k2a) and a second spring rate (k2b) . Further, effective spring rate (Ki) of the first compression spring (23) may be derived by the following equation:
_ Kla * K2a Kla + K2a
Similarly, effective spring rate (K2) of the second compression spring (24) may be derived by the following equation:
_ K2a * K2b ^2a + K2b
[056] Further, magnitude of the second spring rate (kib and k2b) may be greater than magnitude of the first spring rate (kiaandk2a). By virtue of the above-described configuration of the springs (23 and 24) including different spring rates, the first compression spring (23) may have a higher compression than the compression of

the second compression spring (24). Alternatively, the first compression spring (23) may have a lower compression than the compression of the second compression spring (24). The spring rates (kia, kit,, k2a, and k2b) of the first portions (28a, 29a) and the second portions (28b, 29b) of the first compression spring (23) and the second compression spring (24) is dependent on parameters such as, but not limited to number of coils, wire diameter, pitch, and material of the springs (23, 24).
[057] Furthermore, effective spring rate of the system (15) (with the springs (23 and 24 arranged in parallel to each other) may be derived by the following equation:
Ke = ^1 + K2
Effective spring rate of the system (15) is dependent on parameters such as, but not limited, at least one of a length and position of the first portion (28a, 28b) and the second portion (29a, 29b) of each of the first compression spring (23) and the second compression spring (24), respectively.
[058] By virtue of the above-described configuration of the springs (23 and 24) included in the damping units (21 and 22), the system (15) is configured to have a progressive spring rate with a plurality of changeover points. The term 'progressive spring rate' as used herein refers to a phenomenon of change (may be a gradual change or sharp change) in effective spring rate of the system (15). In an embodiment, the term 'progressive spring rate' or the change in effective spring rate of the system (15) may refer to an increase in the effective spring rate of the system (15). Change in effective spring rate of the system (15) may take place at the plurality of changeover points. In an embodiment, effective spring rate (Ke) of the system (15) may not change gradually, but changes in a stepwise manner by adding one additional step to the overall stiffness of the system (15). Such configuration results in in a multiple stage stiffness (may be three or more stages of stiffness) system (15) for better progression of the effective spring rate (Ke). The effective spring rate of the system (15) may increase, with increase in load acting on the system (15). That is, the system (15) is configured to have a varying spring rate for varying ranges of load. The system (15) is configured to have an increasing

effective spring rate with increase in load acting on the system (15). The system (15) may be configured such that the spring rate of the springs (23 and 24) increases with increase in load acting on the system (15). The system (15), as depicted in Figures 1 to 4, has two changeover points by virtue of being configured with two asymmetric springs (23 and 24). Further, the term 'changeover point' as used herein refers a load point/range at which there is an increase/change in effective spring rate of the system (15). Such 'changeover point' may be signified by a substantial increase in effective spring rate of the system (15), where the load required for unit compression of the springs (23 and 24) increases substantially.
[059] In an embodiment, the progressive spring rate and the plurality of changeover points are dependent on spring rate of the first compression spring (23) and the second compression spring (24). Further, the progressive spring rate is dependent on magnitude of load acting on each of the first compression spring (23) and the second compression spring (24). Furthermore, the progressive spring rate may be varied by varying length and position of the first portion (28a, 28b) and the second portion (29a, 29b) of each of the first compression spring (23) and the second compression spring (24), whereby varying position of the changeover point of the springs (23 and 24). In an embodiment, each of the first compression spring (23) and the second compression spring (24) may be configured to have more than one changeover point, by configuring the springs (23 and 24) to have multiple portions with varying/different pitch. In such embodiment, the system (15) may have a higher number of changeover points, resulting in higher degree of progressive spring rate.
[060] Figure 5 illustrates a graph of suspension characteristics (represented by curve 30) for a conventional rear suspension system. The conventional rear suspension system includes two identical springs, each of which is accommodated in a damping unit (suspension device) of the conventional rear suspension system. The conventional rear suspension system may include two damping units, each having one spring among the two identical springs. Each of the two identical springs may have a first portion and a second portion. The first portion of each of the two

identical springs may have a first pitch and the second portion of each of the two identical springs may have a second pitch. The first pitch of the first portion is different in comparison with the second pitch of the second portion. Spring rate of each of the two identical springs may be denoted by Kx and KY, respectively. The graph in Figure 5 is a plot of Load (in Newton) versus Stroke (in mm), where stroke refers to magnitude of total compression of the springs of the conventional rear suspension system. As can be seen in Figure 5, the conventional rear suspension system has an initial compression point B, which refers to initial compression of the springs of conventional rear suspension system for an initial load. Further, the conventional rear suspension system has an effective spring rate of Kci for a load range of up to 300 N to 350 N. It is to be noted that the load range values referred to in the description are for purpose of explanation of the embodiments depicted in Figures. However, it is also to be noted that the load range values may be different for different systems and spring configuration of the conventional rear suspension system. Further, the load ranges may also depend on configuration of the vehicle in which the suspension system is employed. Further, the effective spring rate Kci of the conventional rear suspension system (with the springs arranged in parallel) may be calculated as follows:
Kci = Kx + KY As the load increases beyond the load range of up to 300 N to 350 N, the first portion of each the two identical springs may undergo complete compression with no scope for further compression. Subsequent to such complete compression of the first portion of each the two identical springs, suspension characteristic only depends on compression of the second portion of the two identical springs. Accordingly, there is a change in effective spring rate, i.e., changes from Kci to Kc2, where Kc2 is a summation of spring rates of the second portions of the two identical springs (as there is no scope for further compression of the first portion of the springs). Accordingly, the conventional rear suspension system is characterized by a changeover point C, where the effective spring rate changes from Kci to Kc2.

[061] Figure 6 illustrates a graph of suspension characteristics for the system (15) of the present disclosure. The graph in Figure 6 is a plot of Load (in Newton) versus Stroke (in mm), where stroke refers to magnitude of total compression of the springs (23 and 24) of the system (15). Curve 31 and 32 represents suspension characteristics of the first compression spring (23) and the second compression spring (24), respectively. As can be seen in Figure 6, the system (15) has an initial compression point D, which refers to initial compression of the springs (23 and 24) of the system (15) for an initial load. The first compression spring (23) may have a first spring rate (kn) for the first range of load (in range of up to 200 N to 250 N). The first spring rate (kn) is characterized by (or comprises contribution from) compression of both the first portion (28a) and the second portion (29a) of the first compression spring (23). Further, suspension characteristic of the first compression spring (23) is characterized by a changeover point E, where the spring rate changes over to second spring rate (ki2) for a second range of load. The second spring rate (ki2) is characterized by (or comprises contribution from) compression of only the second portion (29a) of the first compression spring (23) (as the first portion (28a) will have undergone complete compression with no further scope for any compression of the coils comprised in first portion (28a)). Furthermore, the second compression spring (24) has a first spring rate (k2i) for the first range of load (in range of up to 400 N to 450 N). The first spring rate (k2i) is characterized by (or comprises contribution from) compression of both the first portion (28b) and the second portion (29b) of the second compression spring (24). Suspension characteristic of the second compression spring (24) is characterized by a changeover point F, where the spring rate changes over to second spring rate (k22) for the second range of load. The second spring rate (k22) is characterized by (or comprises contribution from) compression of only the second portion (29b) of the second compression spring (24) (as the first portion (28b) will have undergone complete compression with no further scope for any compression of the coils comprised in the first portion (28b)). Accordingly, in comparison with the conventional spring system having only one changeover point, the system (15) has two changeover points for the same number of springs. By having two changeover

points, the system (15) exhibits a progressive spring rate (with increase in effective spring rates across varying load ranges) and progressive suspension characteristics, whereby increasing ride comfort for the passengers. Such progressive spring rate with changing suspension characteristics is well illustrated in Figure 7.
[062] Figure 7 illustrates a graph of wheel rate of the vehicle (100) comprising the system (15). The graph in Figure 7 is a plot of suspension rate (in Newton/mm) versus Stroke (in mm), where stroke refers to magnitude of total compression of the springs (23 and 24) of the system (15). Curve 33 represents suspension rate of the conventional suspension system, where it is illustrated that there is only one changeover point 'C (as described earlier, 'B' is initial compression point). On the contrary, the system (15) has two changeover points (E and F) (as described earlier, 'D' is initial compression point), with three effective spring rates Kei, Ke2, and Ke3. The three effective spring rates Kei, Ke2, and Ke3 of the system (15) are dependent on parameters such as, but not limited to, magnitude of load acting on each of the first compression spring (23) and the second compression spring (24), pitch and length and each of the first portion and the second portion of the first compression spring (23) and the second compression spring (24). The first effective spring rate Kei is characterized by (or comprises contribution from) compression of the first portions (28a, 29a) and the second portions (28b, 29b) of each of the first compression spring (23) and the second compression spring (24). Further, the second effective spring rate Ke2 is characterized by (or comprises contribution from) compression of either of the first portions (28a, 29a) (as one among the two first portions (28a or 28b) will be completely compressed, without any further scope for compression of coils comprised therein) of the springs (23, 24) and the second portions (28b, 29b) of each of the first compression spring (23) and the second compression spring (24). Furthermore, the third effective spring rate Ke3 is characterized by (or comprises contribution from) compression of only the second portions (28b, 29b) of each of the first compression spring (23) and the second compression spring (24) (as both the first portions (28a and 28b) of the springs (23 and 24) will be completely compressed, without any further scope for compression

of coils comprised therein). By having two changeover points (E and F), the system (15) exhibits a progressive spring rate (with increase in effective spring rates across varying load ranges) and progressive suspension characteristics, whereby increasing ride comfort for the passengers.
[063] The system (15) is configured to exhibit progressive spring rate with a plurality of changeover points, which makes the suspension characteristic of the system (15) dynamic and adaptable to instant road conditions. In comparison with conventional suspension systems, the system (15) is configured to handle a wide range of road conditions and weight conditions, whereby catering to extensive operational requirements of the vehicle (100). Further, in comparison with the conventional spring system having only one changeover point, the system (15) provides two changeover points for the same number of springs. By having two changeover points, the system (15) exhibits a progressive spring rate and suspension characteristics, whereby increasing ride comfort for the passengers. In comparison with suspension systems that have damping units configured with two springs in each damping unit for achieving plurality of changeover points, the system (15) is configured to provide a similar suspension characteristics (i.e., progressive spring rate with a plurality of changeover points) with only one spring in each damping unit. Such configuration of the system (15) reduces and minimizes costs associated with rear suspension systems of two-wheeled vehicles. By having only one spring in each damping unit, the system (15) has lesser number of moving parts and reduced wear and tear, whereby eliminating requirement of frequent maintenance and servicing of suspension systems.
[064] The various embodiments of the present disclosure have been described above with reference to the accompanying drawings. The present disclosure is not limited to the illustrated embodiments; rather, these embodiments are intended to fully and completely disclose the subject matter of the disclosure to those skilled in this art. In the drawings, like numbers refer to like elements throughout. Thicknesses and dimensions of some components may be exaggerated for clarity.

[065] Herein, the terms "attached", "connected", "interconnected", "contacting", "mounted", "coupled" and the like can mean either direct or indirect attachment or contact between elements, unless stated otherwise.
[066] Well-known functions or constructions may not be described in detail for brevity and/or clarity. As used herein the expression "and/or" includes any and all combinations of one or more of the associated listed items.
[067] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises", "comprising", "includes" and/or "including" when used in this specification, specify the presence of stated features, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, operations, elements, components, and/or groups thereof.
[068] While considerable emphasis has been placed herein on the particular features of this disclosure, it will be appreciated that various modifications can be made, and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. These and other modifications in the nature of the disclosure or the preferred embodiments will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation.
EQUIVALENTS
[069] With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or

application. The various singular/plural permutations may be expressly set forth herein for sake of clarity.
[070] It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as "open" terms (e.g., the term "including" should be interpreted as "including but not limited to," the term "having" should be interpreted as "having at least," the term "includes" should be interpreted as "includes but is not limited to," etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases "at least one" and "one or more" to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles "a" or "an" limits any particular claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases "one or more" or "at least one" and indefinite articles such as "a" or "an" (e.g., "a" and/or "an" should typically be interpreted to mean "at least one" or "one or more"); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of "two recitations," without other modifiers, typically means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogous to "at least one of A, B, and C, etc." is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., "a system (100) having at least one of A, B, and C" would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances where a

convention analogous to "at least one of A, B, or C, etc." is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., "a system (100) having at least one of A, B, or C" would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase "A or B" will be understood to include the possibilities of "A" or "B" or "A and B."
[071] In addition, where features or aspects of the disclosure are described in terms of Markush groups, those skilled in the art will recognize that the disclosure is also thereby described in terms of any individual member or subgroup of members of the Markush group.
[072] While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.

We claim:

1. A rear suspension system (15) for a two-wheeled vehicle (100), comprising:
a first suspension device (21) positioned between a wheel (8) and a body frame (101) of the vehicle (100), the first suspension device (21) having a first compression spring (23); and
a second suspension device (22) positioned between the wheel (8) and the body frame (101) of the vehicle (100), the second suspension device (22) having a second compression spring (24);
wherein, the first compression spring (23) and the second compression spring (24) are configured with different spring rates.
2. The rear suspension system (15) as claimed in claim 1, wherein at least one
of the first compression spring (23) and the second compression spring (24)
comprises:
a first portion (28a, 28b) defined with first pitch and a second portion (29a, 29b) defined with second pitch;
wherein a length of the first portion (28a) and the second portion (29a) of the first compression spring (23) is different from a length of the first portion (28b) and the second portion (29b) of the second compression spring (24).
3. The rear suspension system (15) as claimed in claim 2, wherein a position of the first portion (28a) and the second portion (29a) of the first compression spring (23) is different from a position of the first portion (28b) and the second portion (29b) of the second compression spring (24).
4. The rear suspension system (15) as claimed in claim 1, wherein the second suspension device (22) is configured parallel to the first suspension device (21).

5. The rear suspension system (15) as claimed in claim 1, wherein at least one
of the first suspension device (21) and the second suspension device (22)
comprises:
a damping unit (25a, 25b) comprising a cylinder (26a, 26b) and a piston (27a, 27b) moveable within the cylinder (26a, 26b); wherein,
the first compression spring (23) is positioned coaxially with the cylinder (26a) of the damping unit (25a) of the first suspension device (21); and
the second compression spring (24) is positioned coaxially with the cylinder (26b) of the damping unit (25b) of the second suspension device (22).
6. The rear suspension system (15) as claimed in claim 1, wherein the first compression spring (23) has a first spring rate for a first range of load and a second spring rate for a second range of load.
7. The rear suspension system (15) as claimed in claim 1, wherein the second compression spring (24) has a first spring rate for the first range of load and a second spring rate for the second range of load.
8. The rear suspension system (15) as claimed in claim 6, wherein magnitude of the second range of load is greater than magnitude of the first range of load.
9. The rear suspension system (15) as claimed in claim 6, wherein magnitude of the second spring rate is greater than magnitude of the first spring rate.
10. The rear suspension system (15) as claimed in claim 1, wherein spring rate of the first compression spring (23) and the second compression spring (24) is dependent on length and position of the first portion (28a, 28b) and the

second portion (29a, 29b) of each of the first compression spring (23) and the second compression spring (24), respectively.
11. The rear suspension system (15) as claimed in claim 1, wherein the system (15) is configured to have a progressive spring rate with a plurality of changeover points, and wherein the progressive spring rate and the plurality of changeover points are dependent on spring rate of the first compression spring (23) and the second compression spring (24).
12. The rear suspension system (15) as claimed in claim 11, wherein the progressive spring rate is dependent on magnitude of load acting on each of the first compression spring (23) and the second compression spring (24).
13. The rear suspension system (15) as claimed in claim 11, wherein the progressive spring rate is varied by varying the first pitch and the second pitch of each of the first compression spring (23) and the second compression spring (24), respectively.
14. A two-wheeled vehicle (100), comprising:
a body frame (101) having a front fork (2), a head tube, a down tube and a pair of seat rails;
a seating assembly (5) coupled to the pair of seat rails and mounted on the body frame (101);
a steering handlebar (3) pivotally coupled to the head tube;
a front wheel (4) and a rear wheel (8) rotatably coupled to the body frame (101); and
a rear suspension system (15), comprising:
a first suspension device (21) positioned between awheel (8)
and a body frame (101) of the vehicle (100), the first suspension
device (21) having a first compression spring (23); and

a second suspension device (22) positioned between the wheel (8) and the body frame (101) of the vehicle (100), the second suspension device (22) having a second compression spring (24); wherein, each of the first compression spring (23) and the second compression spring (24) are configured with different spring rates.