TWI853325B - Bicycle rear sprocket assembly - Google Patents

Abstract

A bicycle rear sprocket assembly comprises at least one sprocket having a total tooth number that is equal to or larger than 15. The at least one sprocket includes at least ten internal spline teeth configured to engage with a bicycle hub assembly.

Description

Bicycle rear sprocket assembly

The present invention relates to a rear sprocket assembly for a bicycle.

Cycling is becoming an increasingly popular form of recreation as well as a means of transportation. In addition, cycling has become a very popular competitive sport for both amateurs and professionals. Whether the bicycle is used for recreation, transportation or competition, the bicycle industry is constantly improving the various components of the bicycle. One bicycle component that has been substantially redesigned is the drivetrain.

According to a first aspect of the present invention, a bicycle rear sprocket assembly includes at least one sprocket having a total number of teeth equal to or greater than 15. The at least one sprocket includes at least ten internal spline teeth configured to engage with a bicycle wheel hub assembly. In the case of the bicycle rear sprocket assembly according to the first aspect, the at least ten internal spline teeth reduce the rotational force applied to each of the at least ten internal spline teeth compared to a sprocket including nine or fewer internal spline teeth. This improves the durability of the at least one sprocket and/or improves the freedom to choose the material of the at least one sprocket without reducing the durability of the at least one sprocket. According to a second aspect of the present invention, the bicycle rear sprocket assembly as in the first aspect is configured so that a total number of the at least ten internal spline teeth is equal to or greater than 20. In the case of the bicycle rear sprocket assembly according to the second aspect, at least twenty internal spline teeth reduce the rotational force applied to each of the at least twenty internal spline teeth compared to a sprocket support body including nine or fewer internal spline teeth. This improves the durability of at least one sprocket and/or improves the freedom of selecting the material of at least one sprocket without reducing the durability of at least one sprocket. According to a third aspect of the present invention, the bicycle rear sprocket assembly as in the second aspect is configured so that the total number of the at least ten internal spline teeth is equal to or greater than 25. In the case of a bicycle rear sprocket assembly according to the third aspect, the at least twenty-five inner spline teeth further reduce the rotational force applied to each of the at least twenty-five inner spline teeth compared to a sprocket including nine or fewer inner spline teeth. This further improves the durability of at least one sprocket and/or improves the freedom to choose the material of at least one sprocket without reducing the durability of at least one sprocket. According to a fourth aspect of the present invention, the bicycle rear sprocket assembly as any one of the first to third aspects is configured so that the at least ten inner spline teeth have a first inner pitch angle and a second inner pitch angle different from the first inner pitch angle. In the case of a bicycle rear sprocket assembly according to the fourth aspect, the difference between the first inner pitch angle and the second inner pitch angle helps a user to correctly install the bicycle rear sprocket assembly to a bicycle wheel hub assembly, especially with respect to the circumferential position of each sprocket of the bicycle rear sprocket assembly. According to a fifth aspect of the present invention, the bicycle rear sprocket assembly as in any one of the first to fourth aspects is configured such that the at least one sprocket includes at least ten sprockets. In the case of a bicycle rear sprocket assembly according to the fifth aspect, at least ten sprockets enable a wide range of bicycle rear sprockets. According to a sixth aspect of the present invention, the bicycle rear sprocket assembly of any one of the first to fourth aspects is configured so that the at least one sprocket includes at least eleven sprockets. In the case of the bicycle rear sprocket assembly according to the sixth aspect, at least eleven sprockets achieve a wider range of bicycle rear sprockets. According to a seventh aspect of the present invention, the bicycle rear sprocket assembly of any one of the first to fourth aspects is configured so that the at least one sprocket includes at least twelve sprockets. In the case of the bicycle rear sprocket assembly according to the seventh aspect, at least twelve sprockets achieve a wider range of bicycle rear sprockets. According to an eighth aspect of the present invention, a bicycle rear sprocket assembly as in any one of the first to seventh aspects is configured so that the at least one sprocket includes a plurality of sprockets and at least one internal spline tooth configured to engage with a bicycle wheel hub assembly. The plurality of sprockets includes a largest sprocket having a tooth tip diameter. The at least one internal spline tooth has an internal spline top diameter. A ratio of the internal spline top diameter to the tooth tip diameter is in the range of 0.1 to 0.2. In the case of a bicycle rear sprocket assembly according to the eighth aspect, the ratio achieves a wide range of bicycle rear sprocket assemblies while improving the durability of at least one sprocket. According to a ninth aspect of the present invention, the bicycle rear sprocket assembly of any one of the first to eighth aspects is configured so that the at least one sprocket includes a first sprocket and a second sprocket. The first sprocket has a first total number of teeth. The second sprocket has a second total number of teeth less than the first total number of teeth. The first sprocket includes at least one first shift facilitating region to facilitate a first shifting operation of a bicycle chain from the second sprocket to the first sprocket, and includes at least one second shift facilitating region to facilitate a second shifting operation of the bicycle chain from the first sprocket to the second sprocket. In the case of the bicycle rear sprocket assembly according to the ninth aspect, at least one first shift promoting area and at least one second shift promoting area make the first shifting operation and the second shifting operation smoother. According to the tenth aspect of the present invention, the bicycle rear sprocket assembly as any one of the first to ninth aspects further includes a locking member, which is configured to prevent an axial movement of the at least one sprocket mounted on a bicycle wheel hub assembly relative to a rotational center axis of the bicycle rear sprocket assembly. The locking member includes a tubular main body portion and a protruding portion. The tubular main body portion has a center axis. The protruding portion extends radially outward from the tubular main body portion relative to the center axis of the tubular main body portion. The tubular body portion has an outer threaded portion configured to engage with an inner threaded portion of the bicycle wheel hub assembly. The protruding portion is configured to abut the at least one sprocket. In the case of the bicycle rear sprocket assembly according to the tenth aspect, it is possible to attach the bicycle rear sprocket assembly to the bicycle wheel hub assembly to prevent the at least one sprocket from axially moving relative to the bicycle wheel hub assembly. According to an eleventh aspect of the present invention, the bicycle rear sprocket assembly as in the tenth aspect is configured so that the tubular body portion has a first outer diameter equal to or less than 26 mm. In the case of a bicycle rear sprocket assembly according to the eleventh aspect, the first outer diameter realizes the wide range of the bicycle rear sprocket assembly while preventing axial movement of at least one sprocket relative to the bicycle wheel hub assembly. According to a twelfth aspect of the present invention, the bicycle rear sprocket assembly as in the eleventh aspect is configured so that the first outer diameter is equal to or greater than 25 mm. In the case of a bicycle rear sprocket assembly according to the twelfth aspect, the first outer diameter ensures the strength of the locking member while realizing the wide range of the bicycle rear sprocket assembly. According to a thirteenth aspect of the present invention, the bicycle rear sprocket assembly as in any one of the tenth to twelfth aspects is configured so that the protruding portion has a second outer diameter equal to or less than 32 mm. In the case of a bicycle rear sprocket assembly according to the thirteenth aspect, the second outer diameter realizes the wide range of the bicycle rear sprocket assembly while preventing at least one sprocket from axially moving relative to the bicycle wheel hub assembly. According to the fourteenth aspect of the present invention, the bicycle rear sprocket assembly such as the thirteenth aspect is configured so that the second outer diameter is equal to or greater than 30 mm. In the case of a bicycle rear sprocket assembly according to the fourteenth aspect, the second outer diameter ensures the strength of the locking member while realizing the wide range of the bicycle rear sprocket assembly. According to the fifteenth aspect of the present invention, the bicycle rear sprocket assembly such as any one of the tenth aspect to the fourteenth aspect is configured so that the locking member has a tool engaging portion. In the case of the bicycle rear sprocket assembly according to the fifteenth aspect, it is possible to easily attach the locking member to the bicycle wheel hub assembly and to easily detach the locking member from the bicycle wheel hub assembly. According to the sixteenth aspect of the present invention, the bicycle rear sprocket assembly as in any one of the first to fifteenth aspects further comprises a sprocket support. The at least one sprocket includes a plurality of sprockets attached to the sprocket support. In the case of the bicycle rear sprocket assembly according to the sixteenth aspect, it is possible to reduce the weight of the bicycle rear sprocket assembly. According to the seventeenth aspect of the present invention, the bicycle rear sprocket assembly such as the sixteenth aspect is configured so that the plurality of sprockets are attached to the sprocket support by an adhesive. In the case of the bicycle rear sprocket assembly according to the seventeenth aspect, it is possible to reduce or remove metal fasteners. This effectively reduces the weight of the bicycle rear sprocket assembly. According to the eighteenth aspect of the present invention, the bicycle rear sprocket assembly such as the sixteenth aspect or the seventeenth aspect is configured so that the sprocket support is made of a non-metallic material including a resin material. In the case of the bicycle rear sprocket assembly according to the eighteenth aspect, the non-metallic material more effectively reduces the weight of the bicycle rear sprocket assembly. According to a nineteenth aspect of the present invention, the bicycle rear sprocket assembly of any one of the first to eighteenth aspects further comprises a rear wheel hub adjacent surface, the rear wheel hub adjacent surface being configured to be adjacent to the bicycle wheel hub assembly in an axial direction relative to a rotation center axis of the bicycle rear sprocket assembly when the bicycle rear sprocket assembly is mounted to the bicycle wheel hub assembly. The at least one sprocket includes a plurality of sprockets, the plurality of sprockets including a largest sprocket. The largest sprocket has an axial inner surface and an axial outer surface disposed on an opposite side of the axial inner surface in the axial direction. The axial outer surface is closer to the rear wheel hub adjacent surface in the axial direction than the axial inner surface. An axial distance defined between the axial inner surface and the rear wheel hub adjacent surface in the axial direction is equal to or greater than 7 mm. In the case of the bicycle rear sprocket assembly according to the nineteenth aspect, the axial distance realizes a wide range of bicycle rear sprockets. According to the twentieth aspect of the present invention, the bicycle rear sprocket assembly such as the nineteenth aspect is configured so that the axial distance is equal to or greater than 10 mm. In the case of the bicycle rear sprocket assembly according to the twentieth aspect, the axial distance further realizes a wider range of bicycle rear sprockets. According to the twenty-first aspect of the present invention, a bicycle rear sprocket assembly includes at least one sprocket having a total number of teeth equal to or greater than 15. The at least one sprocket includes at least one internal spline tooth configured to engage with a bicycle wheel hub assembly. The at least one internal spline tooth has an internal spline top diameter equal to or less than 30 mm. In the case of the bicycle rear sprocket assembly according to the twenty-first aspect, it is possible to manufacture a bicycle rear sprocket having a total number of teeth equal to or less than 10. Therefore, it is possible to widen the gear range of the bicycle rear sprocket assembly on the high-speed gear side. The twenty-first aspect can be combined with any one of the first to twentieth aspects. According to the twenty-second aspect of the present invention, the bicycle rear sprocket assembly as in the twenty-first aspect is configured so that the inner spline top diameter is equal to or greater than 25 mm. In the case of the bicycle rear sprocket assembly according to the twenty-second aspect, it is possible to ensure the strength of at least one sprocket while widening the gear range of the bicycle rear sprocket assembly on the high-speed gear side. According to the twenty-third aspect of the present invention, the bicycle rear sprocket assembly as in the twenty-first aspect is configured so that the inner spline top diameter is equal to or greater than 29 mm. In the case of the bicycle rear sprocket assembly according to the twenty-third aspect, it is possible to further ensure the strength of at least one sprocket while widening the gear range of the bicycle rear sprocket assembly on the high-speed gear side. According to the twenty-fourth aspect of the present invention, the bicycle rear sprocket assembly as any one of the twenty-first to twenty-third aspects is configured so that the at least one inner spline tooth has an inner spline bottom diameter equal to or less than 28 mm. In the case of the bicycle rear sprocket assembly according to the twenty-fourth aspect, the inner spline bottom diameter can increase the radial length of the transmission surface of the at least one inner spline tooth. This improves the strength of at least one sprocket. According to the twenty-fifth aspect of the present invention, the bicycle rear sprocket assembly such as the twenty-fourth aspect is configured so that the inner spline bottom diameter is equal to or greater than 25 mm. In the case of the bicycle rear sprocket assembly according to the twenty-fifth aspect, it is possible to ensure the strength of at least one sprocket while widening the gear range of the bicycle rear sprocket assembly on the high-speed gear side. According to the twenty-sixth aspect of the present invention, the bicycle rear sprocket assembly such as the twenty-fourth aspect or the twenty-fifth aspect is configured so that the inner spline bottom diameter is equal to or greater than 27 mm. In the case of the bicycle rear sprocket assembly according to the twenty-sixth aspect, it is possible to surely ensure the strength of at least one sprocket while widening the gear range of the bicycle rear sprocket assembly on the high-speed gear side. According to the twenty-seventh aspect of the present invention, the bicycle rear sprocket assembly as any one of the twenty-first to twenty-sixth aspects is configured so that the at least one inner spline tooth includes a plurality of inner spline teeth, the plurality of inner spline teeth including a plurality of inner spline transmission surfaces for transmitting a transmission rotational force to the bicycle wheel hub assembly during pedaling. The plurality of inner spline transmission surfaces each include a radial outermost edge, a radial innermost edge, and a radial length defined from the radial outermost edge to the radial innermost edge. A sum of the radial lengths is equal to or greater than 7 mm. In the case of a bicycle rear sprocket assembly according to the twenty-seventh aspect, it is possible to increase the radial length of the plurality of inner spline transmission surfaces. This improves the strength of at least one sprocket. According to the twenty-eighth aspect of the present invention, the bicycle rear sprocket assembly as in the twenty-seventh aspect is configured so that the sum of the radial lengths is equal to or greater than 10 mm. In the case of a bicycle rear sprocket assembly according to the twenty-eighth aspect, it is possible to further increase the radial length of the plurality of internal spline transmission surfaces. This improves the strength of at least one sprocket. According to the twenty-ninth aspect of the present invention, the bicycle rear sprocket assembly as in the twenty-seventh aspect is configured so that the sum of the radial lengths is equal to or greater than 15 mm. In the case of a bicycle rear sprocket assembly according to the twenty-ninth aspect, it is possible to further increase the radial length of the plurality of external spline transmission surfaces. This further improves the strength of at least one sprocket. According to the thirtieth aspect of the present invention, the bicycle rear sprocket assembly as in any one of the twenty-first to twenty-ninth aspects is configured so that the at least one sprocket includes at least ten sprockets. In the case of a bicycle rear sprocket assembly according to the 30th aspect, at least ten sprockets realize the wide range of the bicycle rear sprocket assembly. According to the 31st aspect of the present invention, the bicycle rear sprocket assembly as in any one of the 21st to 29th aspects is configured so that the at least one sprocket includes at least eleven sprockets. In the case of a bicycle rear sprocket assembly according to the 31st aspect, at least eleven sprockets realize the wide range of the bicycle rear sprocket assembly. According to the 32nd aspect of the present invention, the bicycle rear sprocket assembly as in any one of the 21st to 29th aspects is configured so that the at least one sprocket includes at least twelve sprockets. In the case of a bicycle rear sprocket assembly according to the thirty-second aspect, at least twelve sprockets realize a wide range of bicycle rear sprocket assembly. According to the thirty-third aspect of the present invention, a bicycle rear sprocket assembly as any one of the twenty-first to thirty-second aspects is configured so that the at least one sprocket includes a plurality of sprockets. The plurality of sprockets includes a largest sprocket having a tooth tip diameter. A ratio of the inner spline top diameter to the tooth tip diameter is in the range of 0.1 to 0.2. In the case of a bicycle rear sprocket assembly according to the thirty-third aspect, the ratio realizes a wide range of bicycle rear sprocket assembly while improving the durability of at least one sprocket. According to the thirty-fourth aspect of the present invention, the bicycle rear sprocket assembly of any one of the twenty-first to thirty-second aspects is configured so that the at least one sprocket includes a first sprocket and a second sprocket. The first sprocket has a first total number of teeth. The second sprocket has a second total number of teeth less than the first total number of teeth. The first sprocket includes at least one first shift facilitating region to facilitate a first shifting operation of a bicycle chain from the second sprocket to the first sprocket, and includes at least one second shift facilitating region to facilitate a second shifting operation of the bicycle chain from the first sprocket to the second sprocket. In the case of a bicycle rear sprocket assembly according to the thirty-fourth aspect, at least one first shift-promoting region and at least one second shift-promoting region make the first shifting operation and the second shifting operation smoother. According to the thirty-fifth aspect of the present invention, the bicycle rear sprocket assembly of any one of the twenty-first to thirty-fourth aspects further comprises a locking member, which is configured to prevent an axial movement of the at least one sprocket mounted on a bicycle wheel hub assembly relative to a rotational center axis of the bicycle rear sprocket assembly. The locking member comprises a tubular main body portion and a protruding portion. The tubular main body portion has a center axis. The protruding portion extends radially outward from the tubular main body portion relative to the center axis of the tubular main body portion. The tubular body portion has an outer threaded portion configured to engage with an inner threaded portion of the bicycle wheel hub assembly. The protruding portion is configured to abut against the at least one sprocket. In the case of a bicycle rear sprocket assembly according to the thirty-fifth aspect, it is possible to attach the bicycle rear sprocket assembly to a bicycle wheel hub assembly to prevent at least one sprocket from axially moving relative to the bicycle wheel hub assembly. According to a thirty-sixth aspect of the present invention, the bicycle rear sprocket assembly of the thirty-fifth aspect is configured so that the tubular body portion has a first outer diameter equal to or less than 26 mm. In the case of a bicycle rear sprocket assembly according to the thirty-sixth aspect, the first outer diameter achieves a wide range of the bicycle rear sprocket assembly while preventing at least one sprocket from axially moving relative to the bicycle wheel hub assembly. According to the thirty-seventh aspect of the present invention, the bicycle rear sprocket assembly such as the thirty-sixth aspect is configured so that the first outer diameter is equal to or greater than 25 mm. In the case of the bicycle rear sprocket assembly according to the thirty-seventh aspect, the first outer diameter ensures the strength of the locking member while achieving the wide range of the bicycle rear sprocket assembly. According to the thirty-eighth aspect of the present invention, the bicycle rear sprocket assembly such as any one of the thirty-fifth aspect to the thirty-seventh aspect is configured so that the protruding portion has a second outer diameter equal to or less than 32 mm. In the case of the bicycle rear sprocket assembly according to the thirty-eighth aspect, the second outer diameter achieves the wide range of the bicycle rear sprocket assembly while preventing at least one sprocket from axially moving relative to the bicycle wheel hub assembly. According to the thirty-ninth aspect of the present invention, the bicycle rear sprocket assembly such as the thirty-eighth aspect is configured so that the second outer diameter is equal to or greater than 30 mm. In the case of the bicycle rear sprocket assembly according to the thirty-ninth aspect, the second outer diameter ensures the strength of the locking member while achieving the wide range of the bicycle rear sprocket assembly. According to the fortieth aspect of the present invention, the bicycle rear sprocket assembly such as any one of the thirty-fifth aspect to the thirty-ninth aspect is configured so that the locking member has a tool engaging portion. In the case of the bicycle rear sprocket assembly according to the fortieth aspect, it is possible to easily attach the locking member to the bicycle wheel hub assembly and to easily detach the locking member from the bicycle wheel hub assembly. According to the 41st aspect of the present invention, the bicycle rear sprocket assembly as any one of the 21st to 40th aspects further includes a sprocket support. The at least one sprocket includes a plurality of sprockets attached to the sprocket support. In the case of the bicycle rear sprocket assembly according to the 41st aspect, it is possible to reduce the weight of the bicycle rear sprocket assembly. According to the 42nd aspect of the present invention, the bicycle rear sprocket assembly as the 41st aspect is configured so that the plurality of sprockets are attached to the sprocket support by an adhesive. In the case of the bicycle rear sprocket assembly according to the 42nd aspect, it is possible to reduce or remove metal fasteners. This effectively reduces the weight of the bicycle rear sprocket assembly. According to the 43rd aspect of the present invention, the bicycle rear sprocket assembly such as the 41st aspect or the 42nd aspect is configured so that the sprocket support is made of a non-metal material including a resin material. In the case of the bicycle rear sprocket assembly according to the 43rd aspect, the non-metal material is more effective in reducing the weight of the bicycle rear sprocket assembly. According to the 44th aspect of the present invention, the bicycle rear sprocket assembly such as any one of the 21st aspect to the 43rd aspect further includes a rear wheel hub adjacent surface, and the rear wheel hub adjacent surface is configured to be adjacent to the bicycle wheel hub assembly in an axial direction relative to a rotation center axis of the bicycle rear sprocket assembly in a state where the bicycle rear sprocket assembly is mounted to the bicycle wheel hub assembly. The at least one sprocket includes a plurality of sprockets, and the plurality of sprockets includes a largest sprocket. The largest sprocket has an axial inner surface and an axial outer surface disposed on an opposite side of the axial inner surface in the axial direction. The axial outer surface is closer to the rear wheel hub adjacent surface in the axial direction than the axial inner surface. An axial distance defined between the axial inner surface and the rear wheel hub adjacent surface in the axial direction is equal to or greater than 7 mm. In the case of the bicycle rear sprocket assembly according to the 44th aspect, the axial distance realizes a wide range of the bicycle rear sprocket. According to the 45th aspect of the present invention, the bicycle rear sprocket assembly such as the 44th aspect is configured so that the axial distance is equal to or greater than 10 mm. In the case of the bicycle rear sprocket assembly according to the 45th aspect, the axial distance further realizes a wider range of the bicycle rear sprocket. According to the 46th aspect of the present invention, a bicycle rear sprocket assembly includes a plurality of sprockets, a rear wheel hub adjacent surface and an axial distance. The plurality of sprockets include a largest sprocket. The largest sprocket has an axial inner surface and an axial outer surface arranged on an opposite side of the axial inner surface in an axial direction relative to a rotation center axis of the bicycle rear sprocket assembly. The rear wheel hub adjacent surface is configured to be adjacent to the bicycle wheel hub assembly in the axial direction in a state where the bicycle rear sprocket assembly is mounted to a bicycle wheel hub assembly, and the axial outer surface is closer to the rear wheel hub adjacent surface in the axial direction than the axial inner surface. The axial distance defined between the axial inner surface and the rear wheel hub adjacent surface in the axial direction is equal to or greater than 7 mm. In the case of the bicycle rear sprocket assembly according to the forty-sixth aspect, the axial distance realizes a wide range of the bicycle rear sprocket. According to a 47th aspect of the present invention, the bicycle rear sprocket assembly such as the 46th aspect is configured so that the axial distance is equal to or greater than 10 mm. In the case of the bicycle rear sprocket assembly according to the 47th aspect, the axial distance further realizes a wider range of bicycle rear sprockets. According to a 48th aspect of the present invention, the bicycle rear sprocket assembly such as the 46th aspect or the 47th aspect is configured so that in a state where the bicycle rear sprocket assembly is mounted to the bicycle wheel hub assembly, the axial inner surface is positioned closer to an axial center plane of the bicycle wheel hub assembly than the rear wheel hub adjacent surface. In the case of a bicycle rear sprocket assembly according to the 48th aspect, the axial distance realizes a wider range of bicycle rear sprockets. According to the 49th aspect of the present invention, the bicycle rear sprocket assembly as in any one of the 46th to 48th aspects is configured so that a total number of the plurality of sprockets is 12. In the case of a bicycle rear sprocket assembly according to the 49th aspect, the total number of the plurality of sprockets realizes a wide range of bicycle rear sprockets. According to the 50th aspect of the present invention, the bicycle rear sprocket assembly as in any one of the 46th to 49th aspects is configured so that a total number of teeth of the largest sprocket is equal to or greater than 39. In the case of the bicycle rear sprocket assembly according to the fiftieth aspect, the total number of teeth of the largest sprocket realizes a wide range of bicycle rear sprockets. According to the fifty-first aspect of the present invention, the bicycle rear sprocket assembly of any one of the forty-sixth aspect to the forty-ninth aspect is configured so that the total number of teeth of the largest sprocket is equal to or greater than 45. In the case of the bicycle rear sprocket assembly according to the fifty-first aspect, the total number of teeth of the largest sprocket realizes a wider range of bicycle rear sprockets.

This application is a continuation-in-part of U.S. Patent Application No. 15/608,924 filed on May 30, 2017. The contents of the application are incorporated herein by reference in their entirety. An embodiment will now be described with reference to the accompanying drawings, in which similar reference numerals designate corresponding or identical elements in the various drawings. First, referring to Figure 1, a bicycle transmission system 10 according to one embodiment includes a bicycle wheel hub assembly 12 and a bicycle rear sprocket assembly 14. The bicycle wheel hub assembly 12 is secured to a bicycle frame BF. The bicycle rear sprocket assembly 14 is mounted on the bicycle wheel hub assembly 12. A bicycle brake rotor 16 is mounted on the bicycle wheel hub assembly 12. The bicycle transmission system 10 further includes a crank assembly 18 and a bicycle chain 20. The crank assembly 18 includes a crank axle 22, a right crank arm 24, a left crank arm 26, and a front sprocket 27. The right crank arm 24 and the left crank arm 26 are fastened to the crank axle 22. The front sprocket 27 is fastened to at least one of the crank axle 22 and the right crank arm 24. The bicycle chain 20 engages with the front sprocket 27 and the bicycle rear sprocket assembly 14 to transmit the pedaling force from the front sprocket 27 to the bicycle rear sprocket assembly 14. The crank assembly 18 includes the front sprocket 27 as a single sprocket in the illustrated embodiment. However, the crank assembly 18 may include a plurality of front sprockets. The bicycle rear sprocket assembly 14 is a rear sprocket assembly. However, the structure of the bicycle rear sprocket assembly 14 can be applied to the front sprocket. In the present application, the following directional terms "front", "rear", "forward", "rearward", "left", "right", "lateral", "upward", and "downward", and any other similar directional terms refer to those directions based on a user (e.g., a rider) sitting on a seat (not shown) of a bicycle and facing the handlebars (not shown). Therefore, these terms, when used to describe the bicycle transmission system 10, the bicycle wheel hub assembly 12, or the bicycle rear sprocket assembly 14, should be interpreted with respect to a bicycle equipped with the bicycle transmission system 10, the bicycle wheel hub assembly 12, or the bicycle rear sprocket assembly 14 as used in an upright riding position on a horizontal surface. As seen in FIGS. 2 and 3 , the bicycle wheel hub assembly 12 and the bicycle rear sprocket assembly 14 have a rotation center axis A1. The bicycle rear sprocket assembly 14 is rotatably supported by the bicycle wheel hub assembly 12 about the rotation center axis A1 relative to the bicycle frame BF ( FIG. 1 ). The bicycle rear sprocket assembly 14 is configured to engage with the bicycle chain 20 to transmit a transmission rotational force F1 between the bicycle chain 20 and the bicycle rear sprocket assembly 14 during pedaling. During pedaling, the bicycle rear sprocket assembly 14 rotates about the rotation center axis A1 in a transmission rotational direction D11. The transmission rotation direction D11 is defined along the circumferential direction D1 of the bicycle wheel hub assembly 12 or the bicycle rear sprocket assembly 14. The reverse rotation direction D12 is the opposite direction of the transmission rotation direction D11 and is defined along the circumferential direction D1. As seen in FIG. 2 , the bicycle wheel hub assembly 12 includes a sprocket support body 28. The bicycle rear sprocket assembly 14 is mounted on the sprocket support body 28 to transmit a transmission rotation force F1 between the sprocket support body 28 and the bicycle rear sprocket assembly 14. The bicycle wheel hub assembly 12 further includes a wheel hub axle 30. The sprocket support body 28 is rotatably mounted on the wheel hub axle 30 around a rotation center axis A1. The bicycle rear sprocket assembly 14 further includes a locking member 32. The locking member 32 is fastened to the sprocket support body 28 to hold the bicycle rear sprocket assembly 14 relative to the sprocket support body 28 in an axial direction D2 parallel to the rotation center axis A1. As seen in FIG. 4 , the bicycle wheel hub assembly 12 is fastened to the bicycle frame BF by the wheel fastening structure WS. The wheel hub axle 30 has a through hole 30A. The fastening rod WS1 of the wheel fastening structure WS extends through the through hole 30A of the wheel hub axle 30. The wheel hub axle 30 includes a first shaft end 30B and a second shaft end 30C. The wheel hub axle 30 extends along the rotation center axis A1 between the first axis end 30B and the second axis end 30C. The first axis end 30B is disposed in the first groove BF11 of the first frame BF1 of the bicycle frame BF. The second axis end 30C is disposed in the second groove BF21 of the second frame BF2 of the bicycle frame BF. The wheel hub axle 30 is fixed between the first frame BF1 and the second frame BF2 by the wheel fastening structure WS. The wheel fastening structure WS includes a structure known in the applied bicycle. Therefore, for the sake of brevity, it will not be described in detail here. As seen in Figures 4 and 5, the bicycle wheel hub assembly 12 further includes a brake rotor support body 34. The brake rotor support body 34 is rotatably mounted on the wheel hub axle 30 about a rotation center axis A1. The brake rotor support body 34 is coupled to the bicycle brake rotor 16 (FIG. 1) to transmit the braking rotational force from the bicycle brake rotor 16 to the brake rotor support body 34. As seen in FIG. 5, the bicycle wheel hub assembly 12 further includes a wheel hub body 36. The wheel hub body 36 is rotatably mounted on the wheel hub axle 30 about a rotation center axis A1. In this embodiment, the sprocket support body 28 is a separate component from the wheel hub body 36. The brake rotor support body 34 is integrally provided with the wheel hub body 36 as a one-piece, unitary component. However, the sprocket support body 28 may be integrally provided with the wheel hub body 36. The brake rotor support body 34 may be a separate member from the wheel hub body 36. The wheel hub body 36 includes a first flange 36A and a second flange 36B. A first wheel hub (not shown) is coupled to the first flange 36A. A second wheel hub (not shown) is coupled to the second flange 36B. The second flange 36B is spaced apart from the first flange 36A in the axial direction D2. The first flange 36A is provided between the sprocket support body 28 and the second flange 36B in the axial direction D2. The second flange 36B is disposed between the first flange 36A and the brake rotor support body 34 in the axial direction D2. The locking member 32 includes an outer threaded portion 32A. The sprocket support body 28 includes an inner threaded portion 28A. In a state where the locking member 32 is fastened to the sprocket support body 28, the outer threaded portion 32A is threadedly engaged with the inner threaded portion 28A. As seen in FIG. 6 , the locking member 32 is configured to prevent at least one sprocket mounted on the bicycle wheel hub assembly 12 from axially moving relative to the rotational center axis A1 of the bicycle rear sprocket assembly 14. As seen in FIG5 , the locking member 32 includes a tubular main body portion 32C and a protruding portion 32B. The tubular main body portion 32C has a center axis A2. The protruding portion 32B extends radially outward from the tubular main body portion 32C relative to the center axis A2 of the tubular main body portion 32C. The tubular main body portion 32C has an outer threaded portion 32A configured to engage with the inner threaded portion 28A of the bicycle wheel hub assembly 12. As seen in FIG6 , the protruding portion 32B is configured to abut at least one sprocket. In this embodiment, the protruding portion 32B is configured to abut the sprocket SP1. The tubular main body portion 32C has a first outer diameter ED1 equal to or less than 26 mm. The first outer diameter ED1 is equal to or greater than 25 mm. In this embodiment, the first outer diameter ED1 is 25.45 mm. However, the first outer diameter ED1 is not limited to this embodiment and the above range. The protrusion 32B has a second outer diameter ED2 equal to or less than 32 mm. The second outer diameter ED2 is equal to or greater than 30 mm. In this embodiment, the second outer diameter ED2 is 31.5 mm. However, the second outer diameter ED2 is not limited to this embodiment and the above range. As seen in Figure 5, the locking member 32 has a tool engaging portion 32D. The tool engaging portion 32D is arranged on the inner peripheral surface 32C1 of the tubular main body portion 32C to engage with the tool. The tool engaging portion 32D includes a plurality of tool engaging grooves 32D1 arranged on the inner peripheral surface 32C1 of the tubular main body portion 32C. However, the structure of the tool engaging portion 32D is not limited to this embodiment. In the illustrated embodiment, the tool engaging portion 32D may be omitted from the locking member 32, or may have another shape different from the tool engaging portion 32D. As seen in FIG. 6 , the bicycle wheel hub assembly 12 further includes a ratchet structure 38. The sprocket support body 28 is operably coupled to the wheel hub body 36 by the ratchet structure 38. The ratchet structure 38 is configured to couple the sprocket support body 28 to the wheel hub body 36, thereby rotating the sprocket support body 28 together with the wheel hub body 36 in the transmission rotation direction D11 ( FIG. 5 ) during pedaling. The ratchet structure 38 is configured to allow the sprocket support body 28 to rotate relative to the wheel hub body 36 in the reverse rotation direction D12 (Figure 5) during idling. Therefore, the ratchet structure 38 can be interpreted as a one-way coupling structure 38. The ratchet structure 38 includes a structure known in the bicycle field. Therefore, for the sake of brevity, it will not be described in detail here. The bicycle wheel hub assembly 12 includes a first bearing 39A and a second bearing 39B. The first bearing 39A and the second bearing 39B are arranged between the sprocket support body 28 and the wheel hub shaft 30 to rotatably support the sprocket support body 28 relative to the wheel hub shaft 30 around the rotation center axis A1. In this embodiment, each of the sprocket support body 28, the brake rotor support body 34, and the hub body 36 is made of a metal material such as aluminum, iron, or titanium. However, at least one of the sprocket support body 28, the brake rotor support body 34, and the hub body 36 may be made of a non-metallic material. As seen in FIGS. 7 and 8, the sprocket support body 28 includes at least one external spline tooth 40 configured to engage with the bicycle rear sprocket assembly 14 (FIG. 6). The sprocket support body 28 includes a plurality of external spline teeth 40 configured to engage with the bicycle rear sprocket assembly 14 (FIG. 6). That is, at least one external spline tooth 40 includes a plurality of external spline teeth 40. The sprocket support body 28 includes at least nine external spline teeth 40 configured to engage with the bicycle rear sprocket assembly 14 (FIG. 6). The sprocket support body 28 includes at least ten external spline teeth 40 configured to engage with the bicycle rear sprocket assembly 14 (FIG. 6). The sprocket support body 28 includes a base support member 41 having a tubular shape. The base support member 41 extends along the rotation center axis A1. The external spline teeth 40 extend radially outward from the base support member 41. The sprocket support body 28 includes a larger diameter portion 42, a flange 44, and a plurality of spiral external spline teeth 46. The larger diameter portion 42 and the flange 44 extend radially outward from the base support member 41. The larger diameter portion 42 is disposed between the plurality of external spline teeth 40 and the flange 44 in the axial direction D2. The larger diameter portion 42 and the flange 44 are disposed between the plurality of external spline teeth 40 and the plurality of spiral external spline teeth 46 in the axial direction D2. As seen in FIG6 , the bicycle rear sprocket assembly 14 is retained in the axial direction D2 between the larger diameter portion 42 and the protruding portion 32B of the locking member 32. The larger diameter portion 42 may have an internal cavity so that a transmission structure such as a one-way coupling structure may be accommodated in the internal cavity. The larger diameter portion 42 may be omitted from the bicycle wheel hub assembly 12 as desired. As seen in FIG9 , the total number of the at least ten external spline teeth 40 is equal to or greater than 20. The total number of the at least ten external spline teeth 40 is equal to or greater than 25. In this embodiment, the total number of the at least ten external spline teeth 40 is 26. However, the total number of external spline teeth 40 is not limited to this embodiment and the above range. At least ten external spline teeth 40 have a first external pitch angle PA11 and a second external pitch angle PA12. At least two of the plurality of external spline teeth 40 are circumferentially arranged at the first external pitch angle PA11 relative to the rotation center axis A1 of the bicycle wheel hub assembly 12. At least two of the plurality of external spline teeth 40 are circumferentially arranged at the second external pitch angle PA12 relative to the rotation center axis A1 of the bicycle wheel hub assembly 12. In this embodiment, the second external pitch angle PA12 is different from the first external pitch angle PA11. However, the second external pitch angle PA12 may be substantially equal to the first external pitch angle PA11. In this embodiment, the external spline teeth 40 are configured at a first external pitch angle PA11 in the circumferential direction D1. Two of the external spline teeth 40 are configured at a second external pitch angle PA12 in the circumferential direction D1. However, at least two of the external spline teeth 40 may be configured at another external pitch angle in the circumferential direction D1. The first external pitch angle PA11 is in the range of 10 to 20 degrees. The first external pitch angle PA11 is in the range of 12 to 15 degrees. The first external pitch angle PA11 is in the range of 13 to 14 degrees. In this embodiment, the first external pitch angle PA11 is 13.3 degrees. However, the first external pitch angle PA11 is not limited to this embodiment and the above range. The second pitch angle PA12 is in the range of 5 to 30 degrees. In this embodiment, the second external pitch angle PA12 is 26 degrees. However, the second external pitch angle PA12 is not limited to this embodiment and the above range. The external spline teeth 40 have shapes that are substantially the same as each other. The external spline teeth 40 have spline sizes that are substantially the same as each other. When viewed along the rotation center axis A1, the external spline teeth 40 have profiles that are substantially the same as each other. However, as seen in Figure 10, at least one of the at least ten external spline teeth 40 may have a first spline shape that is different from the second spline shape of another of the at least ten external spline teeth 40. At least one of the at least ten external spline teeth 40 may have a first spline size that is different from the second spline size of another of the at least ten external spline teeth 40. When viewed along the rotation center axis A1, at least one of the at least ten external spline teeth 40 may have a profile different from the profile of another of the at least ten external spline teeth 40. In FIG. 10 , one of the external spline teeth 40 has a spline shape different from the spline shapes of the other teeth of the external spline teeth 40. One of the external spline teeth 40 has a spline size different from the spline size of the other teeth of the external spline teeth 40. When viewed along the rotation center axis A1, one of the external spline teeth 40 has a profile different from the profile of the other teeth of the external spline teeth 40. As seen in FIG. 11 , each of the at least ten external spline teeth 40 has an external spline transmission surface 48 and an external spline non-transmission surface 50. The plurality of external spline teeth 40 include a plurality of external spline transmission surfaces 48 for receiving the transmission rotational force F1 from the bicycle rear sprocket assembly 14 ( FIG. 6 ) during pedaling. The plurality of external spline teeth 40 include a plurality of external spline non-transmission surfaces 50. The external spline transmission surfaces 48 may contact the bicycle rear sprocket assembly 14 to receive the transmission rotational force F1 from the bicycle rear sprocket assembly 14 ( FIG. 6 ) during pedaling. The external spline transmission surfaces 48 face in the reverse rotational direction D12. The external spline non-transmission surface 50 is disposed on the opposite side of the external spline transmission surface 48 in the circumferential direction D1. The external spline non-transmission surface 50 faces the transmission rotation direction D11, so as not to receive the transmission rotation force F1 from the bicycle rear sprocket assembly 14 during pedaling. At least ten external spline teeth 40 have a circumferential maximum width MW1, respectively. The external spline teeth 40 have a circumferential maximum width MW1, respectively. The circumferential maximum width MW1 is defined as the maximum width that receives the thrust F2 applied to the external spline teeth 40. The circumferential maximum width MW1 is defined as a straight line distance based on the external spline transmission surface 48. The plurality of external spline transmission surfaces 48 each include a radial outermost edge 48A and a radial innermost edge 48B. The external spline transmission surface 48 extends from the radial outermost edge 48A to the radial innermost edge 48B. The first reference circle RC11 is defined on the radial innermost edge 48B and is centered on the rotation center axis A1. The first reference circle RC11 intersects the external spline non-transmission surface 50 at the reference point 50R. The circumferential maximum width MW1 extends from the radial innermost edge 48B to the reference point 50R in the circumferential direction D1. The plurality of external spline non-transmission surfaces 50 each include a radial outermost edge 50A and a radial innermost edge 50B. The external spline non-transmission surface 50 extends from the radial outermost edge 50A to the radial innermost edge 50B. The reference point 50R is set between the radial outermost edge 50A and the radial innermost edge 50B. However, the reference point 50R may coincide with the radial innermost edge 50B. The sum of the circumferential maximum widths MW1 is equal to or greater than 55 mm. The sum of the circumferential maximum widths MW1 is equal to or greater than 60 mm. The sum of the circumferential maximum widths MW1 is equal to or greater than 65 mm. In this embodiment, the sum of the circumferential maximum widths MW1 is 68 mm. However, the sum of the circumferential maximum widths MW1 is not limited to this embodiment and the above range. As seen in FIG. 12 , at least one external spline tooth 40 has an external spline top diameter DM11. The external spline top diameter DM11 is equal to or greater than 25 mm. The external spline top diameter DM11 is equal to or greater than 29 mm. The external spline top diameter DM11 is equal to or less than 30 mm. In this embodiment, the external spline top diameter DM11 is 29.6 mm. However, the external spline top diameter DM11 is not limited to this embodiment and the above range. At least one external spline tooth 40 has an external spline bottom diameter DM12. At least one external spline tooth 40 has an external spline tooth root circle RC12, and the external spline tooth root circle RC12 has an external spline bottom diameter DM12. However, the external spline tooth root circle RC12 may have another diameter different from the external spline bottom diameter DM12. The external spline bottom diameter DM12 is equal to or less than 28 mm. The external spline bottom diameter DM12 is equal to or greater than 25 mm. The external spline bottom diameter DM12 is equal to or greater than 27 mm. In this embodiment, the external spline bottom diameter DM12 is 27.2 mm. However, the external spline bottom diameter DM12 is not limited to this embodiment and the above range. The larger diameter portion 42 has an outer diameter DM13 that is larger than the outer spline top diameter DM11. The outer diameter DM13 is in the range of 32 mm to 40 mm. In this embodiment, the outer diameter DM13 is 35 mm. However, the outer diameter DM13 is not limited to this embodiment. As seen in FIG. 11 , each of the plurality of external spline drive surfaces 48 includes a radial length RL11 defined from a radial outermost edge 48A to a radial innermost edge 48B. The sum of the radial lengths RL11 of the plurality of external spline drive surfaces 48 is equal to or greater than 7 mm. The sum of the radial lengths RL11 is equal to or greater than 10 mm. The sum of the radial lengths RL11 is equal to or greater than 15 mm. In this embodiment, the sum of the radial lengths RL11 is 19.5 mm. However, the sum of the radial lengths RL11 is not limited to this embodiment. The plurality of external spline teeth 40 have radial lengths RL12. The radial lengths RL12 are defined from the external spline tooth root circle RC12 to the radial outermost ends 40A of the plurality of external spline teeth 40, respectively. The sum of the radial lengths RL12 is equal to or greater than 12 mm. In this embodiment, the sum of the radial lengths RL12 is 31.85 mm. However, the sum of the radial lengths RL12 is not limited to this embodiment. At least one of the at least nine external spline teeth 40 has an asymmetric shape relative to the circumferential tooth tip centerline CL1. The circumferential tooth tip centerline CL1 is a line connecting the rotation center axis A1 and the circumferential center point CP1 of the radial outermost end 40A of the external spline tooth 40. However, at least one of the external spline teeth 40 may have a symmetric shape relative to the circumferential tooth tip centerline CL1. At least one of the at least nine external spline teeth 40 includes an external spline driving surface 48 and an external spline non-driving surface 50. The external spline driving surface 48 has a first external spline surface angle AG11. The first external spline surface angle AG11 is defined between the external spline driving surface 48 and the first radial line L11. The first radial line L11 extends from the rotation center axis A1 of the bicycle wheel hub assembly 12 to the radial outermost edge 48A of the external spline drive surface 48. The first external pitch angle PA11 or the second external pitch angle PA12 is defined between adjacent first radial lines L11 (see, for example, FIG. 9). The external spline non-drive surface 50 has a second external spline surface angle AG12. The second external spline surface angle AG12 is defined between the external spline non-drive surface 50 and the second radial line L12. The second radial line L12 extends from the rotation center axis A1 of the bicycle wheel hub assembly 12 to the radial outermost edge 50A of the external spline non-drive surface 50. In this embodiment, the second external spline surface angle AG12 is different from the first external spline surface angle AG11. The first external spline surface angle AG11 is smaller than the second external spline surface angle AG12. However, the first external spline surface angle AG11 may be equal to or greater than the second external spline surface angle AG12. The first external spline surface angle AG11 is in the range of 0 to 10 degrees. The second external spline surface angle AG12 is in the range of 0 to 60 degrees. In this embodiment, the first external spline surface angle AG11 is 5 degrees. The second external spline surface angle AG12 is 45 degrees. However, the first external spline surface angle AG11 and the second external spline surface angle AG12 are not limited to this embodiment and the above ranges. As seen in FIGS. 13 and 14 , the brake rotor support body 34 includes at least one additional external spline tooth 52 configured to engage with the bicycle brake rotor 16 ( FIG. 4 ). In this embodiment, the brake rotor support body 34 includes an additional base support member 54 and a plurality of additional external spline teeth 52. The additional base support member 54 has a tubular shape and extends from the hub body 36 along the rotation center axis A1. The additional external spline teeth 52 extend radially outward from the additional base support member 54. The total number of additional external spline teeth 52 is 52. However, the total number of additional external spline teeth 52 is not limited to this embodiment. As seen in FIG14 , at least one additional external spline tooth 52 has an additional external spline top diameter DM14. As seen in FIG15 , the additional external spline top diameter DM14 is larger than the external spline top diameter DM11. The additional external spline top diameter DM14 is substantially equal to the outer diameter DM13 of the larger diameter portion 42. However, the additional external spline top diameter DM14 may be equal to or smaller than the external spline top diameter DM11. The additional external spline top diameter DM14 may be different from the outer diameter DM13 of the larger diameter portion 42. As seen in FIG. 16 , the wheel hub axle 30 includes an axial contact surface 30B1 for contacting the bicycle frame BF. In this embodiment, the axial contact surface 30B1 can contact the first frame BF1 of the bicycle frame BF. The first frame BF1 includes a frame contact surface BF12. In a state where the bicycle wheel hub assembly 12 is fastened to the bicycle frame BF by the wheel fastening structure WS, the axial contact surface 30B1 contacts the frame contact surface BF12. The first axial length AL11 is defined from the axial contact surface 30B1 to the larger diameter portion 42 in the axial direction D2 relative to the rotation center axis A1. The first axial length AL11 is in the range of 35 mm to 41 mm. The first axial length AL11 may be equal to or greater than 39 mm. The first axial length AL11 may also be in the range of 35 mm to 37 mm. In this embodiment, the first axial length AL11 is 36.2 mm. However, the first axial length AL11 is not limited to this embodiment and the above range. The larger diameter portion 42 has an axial end 42A farthest from the axial contact surface 30B1 in the axial direction D2. The second axial length AL12 is defined from the axial contact surface 30B1 to the axial end 42A in the axial direction D2. The second axial length AL12 is in the range of 38 mm to 47 mm. The second axial length AL12 may be in the range of 44 mm to 45 mm. The second axial length AL12 may also be in the range of 40 mm to 41 mm. In this embodiment, the second axial length AL12 is 40.75 mm. However, the second axial length AL12 is not limited to this embodiment and the above range. The axial length AL13 of the larger diameter portion 42 is in the range of 3 mm to 6 mm. In this embodiment, the axial length AL13 is 4.55 mm. However, the axial length AL13 is not limited to this embodiment and the above range. As seen in Figure 17, the bicycle rear sprocket assembly 14 includes at least one sprocket. At least one sprocket includes a plurality of sprockets. At least one sprocket includes at least ten sprockets. At least one sprocket includes at least eleven sprockets. At least one sprocket includes at least twelve sprockets. The plurality of sprockets include a largest sprocket SP12. The largest sprocket SP12 has a tooth tip diameter TD1. The plurality of sprockets also include a smallest sprocket SP1. The smallest sprocket SP1 may also be referred to as sprocket SP1. The largest sprocket SP12 may also be referred to as sprocket SP12. In this embodiment, at least one sprocket further includes sprockets SP2 to SP11. Sprocket SP1 corresponds to a high-speed gear. Sprocket SP12 corresponds to a low-speed gear. In this embodiment, the total number of the plurality of sprockets is 12. However, the total number of sprockets of the bicycle rear sprocket assembly 14 is not limited to this embodiment. The smallest sprocket SP1 includes at least one sprocket gear SP1B. The total number of at least one sprocket gear SP1B of the smallest sprocket SP1 is equal to or less than 10. In this embodiment, the total number of at least one sprocket gear SP1B of the smallest sprocket SP1 is 10. However, the total number of at least one sprocket gear SP1B of the smallest sprocket SP1 is not limited to this embodiment and the above range. The largest sprocket SP12 includes at least one sprocket gear SP12B. The total number of teeth of the largest sprocket SP12 is equal to or greater than 39. The total number of teeth of the largest sprocket SP12 is equal to or greater than 45. The total number of at least one sprocket gear SP12B of the largest sprocket SP12 is equal to or greater than 46. The total number of at least one sprocket gear SP12B of the largest sprocket SP12 is equal to or greater than 50. In this embodiment, the total number of at least one sprocket gear SP12B of the largest sprocket SP12 is 51. However, the total number of at least one sprocket gear SP12B of the largest sprocket SP12 is not limited to this embodiment and the above range. The tooth tip diameter TD1 is the diameter of the circle defined by the tooth tip of the sprocket gear SP12B. The sprocket SP2 includes at least one sprocket gear SP2B. The sprocket SP3 includes at least one sprocket gear SP3B. The sprocket SP4 includes at least one sprocket gear SP4B. The sprocket SP5 includes at least one sprocket gear SP5B. Sprocket SP6 includes at least one sprocket gear SP6B. Sprocket SP7 includes at least one sprocket gear SP7B. Sprocket SP8 includes at least one sprocket gear SP8B. Sprocket SP9 includes at least one sprocket gear SP9B. Sprocket SP10 includes at least one sprocket gear SP10B. Sprocket SP11 includes at least one sprocket gear SP11B. The total number of at least one sprocket gear SP2B is 12. The total number of at least one sprocket gear SP3B is 14. The total number of at least one sprocket gear SP4B is 16. The total number of at least one sprocket gear SP5B is 18. The total number of at least one sprocket gear SP6B is 21. The total number of at least one sprocket gear SP7B is 24. The total number of at least one sprocket gear SP8B is 28. The total number of at least one sprocket gear SP9B is 33. The total number of at least one sprocket gear SP10B is 39. The total number of at least one sprocket gear SP11B is 45. At least one sprocket has a total number of teeth equal to or greater than 15. For example, the total number of teeth of sprocket SP4 is 16. The total number of teeth of sprocket SP5 is 18. The total number of teeth of sprocket SP6 is 21. The total number of teeth of sprocket SP7 is 24. The total number of teeth of sprocket SP8 is 28. The total number of teeth of sprocket SP9 is 33. The total number of teeth of sprocket SP10 is 39. The total number of teeth of sprocket SP11 is 45. The total number of teeth of sprocket SP12 is 51. The total number of sprocket teeth of each of sprockets SP2 to SP11 is not limited to this embodiment. At least one of sprockets SP1 to SP12 may include a total number of teeth equal to or greater than 15. As seen in FIG. 18 , sprockets SP1 to SP12 are separate components from each other. However, at least one of sprockets SP1 to SP12 may be at least partially provided integrally with another of sprockets SP1 to SP12. The bicycle rear sprocket assembly 14 further includes a sprocket support member 56, a plurality of spacers 58, a first ring 59A, and a second ring 59B. In the illustrated embodiment, a plurality of sprockets SP1 to SP12 are attached to the sprocket support 56. For example, the plurality of sprockets SP1 to SP12 are attached to the sprocket support 56 by an adhesive. As seen in FIG. 19 , sprocket SP1 includes a sprocket body SP1A and a plurality of sprocket gears SP1B. The plurality of sprocket gears SP1B extend radially outward from the sprocket body SP1A. Sprocket SP2 includes a sprocket body SP2A and a plurality of sprocket gears SP2B. The plurality of sprocket gears SP2B extend radially outward from the sprocket body SP2A. Sprocket SP3 includes a sprocket body SP3A and a plurality of sprocket gears SP3B. A plurality of sprocket gears SP3B extend radially outward from the sprocket body SP3A. The sprocket SP4 includes a sprocket body SP4A and a plurality of sprocket gears SP4B. A plurality of sprocket gears SP4B extend radially outward from the sprocket body SP4A. The sprocket SP5 includes a sprocket body SP5A and a plurality of sprocket gears SP5B. A plurality of sprocket gears SP5B extend radially outward from the sprocket body SP5A. A first ring 59A is disposed between the sprocket SP3 and the sprocket SP4. A second ring 59B is disposed between the sprocket SP4 and the sprocket SP5. As shown in FIG. 20 , sprocket SP6 includes a sprocket body SP6A and a plurality of sprocket gears SP6B. The plurality of sprocket gears SP6B extend radially outward from the sprocket body SP6A. Sprocket SP7 includes a sprocket body SP7A and a plurality of sprocket gears SP7B. The plurality of sprocket gears SP7B extend radially outward from the sprocket body SP7A. Sprocket SP8 includes a sprocket body SP8A and a plurality of sprocket gears SP8B. The plurality of sprocket gears SP8B extend radially outward from the sprocket body SP8A. As shown in FIG. 21 , sprocket SP9 includes a sprocket body SP9A and a plurality of sprocket gears SP9B. A plurality of sprocket gears SP9B extend radially outward from the sprocket body SP9A. The sprocket SP10 includes a sprocket body SP10A and a plurality of sprocket gears SP10B. A plurality of sprocket gears SP10B extend radially outward from the sprocket body SP10A. The sprocket SP11 includes a sprocket body SP11A and a plurality of sprocket gears SP11B. A plurality of sprocket gears SP11B extend radially outward from the sprocket body SP11A. The sprocket SP12 includes a sprocket body SP12A and a plurality of sprocket gears SP12B. A plurality of sprocket gears SP12B extend radially outward from the sprocket body SP12A. As seen in FIG. 22 , the sprocket support member 56 includes a hub engaging portion 60 and a plurality of support arms 62. The plurality of support arms 62 extend radially outward from the hub engaging portion 60. The support arms 62 include first to eighth attachment portions 62A to 62H. The plurality of spacers 58 include a plurality of first spacers 58A, a plurality of second spacers 58B, a plurality of third spacers 58C, a plurality of fourth spacers 58D, a plurality of fifth spacers 58E, a plurality of sixth spacers 58F, and a plurality of seventh spacers 58G. As seen in FIG. 23 , the first spacer 58A is disposed between the sprocket SP5 and the sprocket SP6. The second spacer 58B is disposed between the sprocket SP6 and the sprocket SP7. The third spacer 58C is disposed between the sprocket SP7 and the sprocket SP8. The fourth spacer 58D is disposed between the sprocket SP8 and the sprocket SP9. The fifth spacer 58E is disposed between the sprocket SP9 and the sprocket SP10. The sixth spacer 58F is disposed between the sprocket SP10 and the sprocket SP11. The seventh spacer 58G is disposed between the sprocket SP11 and the sprocket SP12. The sprocket SP6 and the first spacer 58A are attached to the first attachment portion 62A by an adhesive structure such as an adhesive. The sprocket SP7 and the second spacer 58B are attached to the second attachment portion 62B by an adhesive structure such as an adhesive. The sprocket SP8 and the third spacer 58C are attached to the third attachment portion 62C by an adhesive structure such as an adhesive. The sprocket SP9 and the fourth spacer 58D are attached to the fourth attachment portion 62D by an adhesive structure such as an adhesive. The sprocket SP10 and the fifth spacer 58E are attached to the fifth attachment portion 62E by an adhesive structure such as an adhesive. The sprocket SP11 and the sixth spacer 58F are attached to the sixth attachment portion 62F by an adhesive structure such as an adhesive. The sprocket SP12 and the seventh spacer 58G are attached to the seventh attachment portion 62G by an adhesive structure such as an adhesive. The sprocket SP5 and the second ring 59B are attached to the eighth attachment portion 62H by an adhesive structure such as an adhesive. The hub engaging portion 60, the sprockets SP1 to SP4, the first ring 59A, and the second ring 59B are held between the larger diameter portion 42 and the protruding portion 32B of the locking member 32 in the axial direction D2. In this embodiment, each of the sprockets SP1 to SP12 is made of a metal material such as aluminum, iron, or titanium. Each of the sprocket support 56, the first spacer 58A to the seventh spacer 58G, the first ring 59A, and the second ring 59B is made of a non-metal material such as a resin material. The sprocket support 56 is made of a non-metallic material including a resin material. However, at least one of the sprockets SP1 to SP12 may be at least partially made of a non-metallic material. At least one of the sprocket support 56, the first spacer 58A to the seventh spacer 58G, the first ring 59A and the second ring 59B may be at least partially made of a metal material such as aluminum, iron or titanium. At least one sprocket includes at least one internal spline tooth configured to engage with the bicycle wheel hub assembly 12. As seen in Figures 24 and 25, at least one sprocket includes at least ten internal spline teeth configured to engage with the bicycle wheel hub assembly 12. At least one inner spline tooth includes a plurality of inner spline teeth. Thus, at least one sprocket includes a plurality of inner spline teeth configured to engage with the bicycle wheel hub assembly 12. In this embodiment, the sprocket SP1 includes at least ten inner spline teeth 64 configured to engage with the bicycle wheel hub assembly 12. In this embodiment, the sprocket SP1 includes inner spline teeth 64 configured to engage with the outer spline teeth 40 of the sprocket support body 28 of the bicycle wheel hub assembly 12. The sprocket body SP1A has an annular shape. The inner spline teeth 64 extend radially inward from the sprocket body SP1A. As seen in FIG. 26 , the total number of at least ten inner spline teeth 64 is equal to or greater than 20. The total number of at least ten inner spline teeth 64 is equal to or greater than 25. In this embodiment, the total number of inner spline teeth 64 is 26. However, the total number of inner spline teeth 64 is not limited to this embodiment and the above range. At least ten inner spline teeth 64 have a first inner pitch angle PA21 and a second inner pitch angle PA22. At least two of the plurality of inner spline teeth 64 are circumferentially arranged at the first inner pitch angle PA21 relative to the rotation center axis A1 of the bicycle rear sprocket assembly 14. At least two of the plurality of internal spline teeth 64 are arranged circumferentially at a second internal pitch angle PA22 relative to the rotation center axis A1. In this embodiment, the second internal pitch angle PA22 is different from the first internal pitch angle PA21. However, the second internal pitch angle PA22 may be substantially equal to the first internal pitch angle PA21. In this embodiment, the internal spline teeth 64 are arranged circumferentially at the first internal pitch angle PA21 in the circumferential direction D1. Two of the internal spline teeth 64 are arranged at the second internal pitch angle PA22 in the circumferential direction D1. However, at least two of the internal spline teeth 64 may be arranged at another internal pitch angle in the circumferential direction D1. The first inner pitch angle PA21 is in the range of 10 degrees to 20 degrees. The first inner pitch angle PA21 is in the range of 12 degrees to 15 degrees. The first inner pitch angle PA21 is in the range of 13 degrees to 14 degrees. In this embodiment, the first inner pitch angle PA21 is 13.3 degrees. However, the first inner pitch angle PA21 is not limited to this embodiment and the above range. The second inner pitch angle PA22 is in the range of 5 degrees to 30 degrees. In this embodiment, the second inner pitch angle PA22 is 26 degrees. However, the second inner pitch angle PA22 is not limited to this embodiment and the above range. At least one of the at least ten inner spline teeth 64 has a first spline shape that is different from the second spline shape of another one of the at least ten inner spline teeth 64. At least one of the at least ten internal spline teeth 64 has a first spline size that is different from a second spline size of another of the at least ten internal spline teeth 64. At least one of the at least ten internal spline teeth 64 has a cross-sectional shape that is different from the cross-sectional shape of another of the at least ten internal spline teeth 64. However, as seen in FIG. 27 , the internal spline teeth 64 may have the same shape as one another. The internal spline teeth 64 may have the same size as one another. The internal spline teeth 64 may have the same cross-sectional shape as one another. As seen in FIG. 28 , at least one internal spline tooth 64 includes an internal spline drive surface 66 and an internal spline non-drive surface 68. At least one inner spline tooth 64 includes a plurality of inner spline teeth 64. The plurality of inner spline teeth 64 include a plurality of inner spline transmission surfaces 66 for receiving the transmission rotational force F1 from the bicycle wheel hub assembly 12 ( FIG. 6 ) during pedaling. The plurality of inner spline teeth 64 include a plurality of inner spline non-transmission surfaces 68. The inner spline transmission surfaces 66 may contact the sprocket support body 28 to transmit the transmission rotational force F1 from the sprocket SP1 to the sprocket support body 28 during pedaling. The inner spline transmission surfaces 66 face the transmission rotational direction D11. The inner spline non-transmission surface 68 is disposed on the opposite side of the inner spline transmission surface 66 in the circumferential direction D1. The inner spline non-transmission surface 68 faces the reverse rotational direction D12 so as not to transmit the transmission rotational force F1 from the sprocket SP1 to the sprocket support body 28 during pedaling. At least ten inner spline teeth 64 have a circumferential maximum width MW2, respectively. The inner spline teeth 64 have a circumferential maximum width MW2, respectively. The circumferential maximum width MW2 is defined as the maximum width for receiving the thrust F3 applied to the inner spline teeth 64. The circumferential maximum width MW2 is defined as a straight line distance based on the inner spline transmission surface 66. The inner spline transmission surface 66 includes a radial outermost edge 66A and a radial innermost edge 66B. The inner spline transmission surface 66 extends from the radial outermost edge 66A to the radial innermost edge 66B. The second reference circle RC21 is defined on the radial outermost edge 66A and is centered on the rotation center axis A1. The second reference circle RC21 intersects the inner spline non-transmission surface 68 at the reference point 68R. The circumferential maximum width MW2 extends from the radial innermost edge 66B in a straight line to the reference point 68R in the circumferential direction D1. The inner spline non-transmission surface 68 includes a radial outermost edge 68A and a radial innermost edge 68B. The inner spline non-transmission surface 68 extends from the radial outermost edge 68A to the radial innermost edge 68B. The reference point 68R is set between the radial outermost edge 68A and the radial innermost edge 68B. The sum of the circumferential maximum widths MW2 is equal to or greater than 40 mm. The sum of the circumferential maximum widths MW2 is equal to or greater than 45 mm. The sum of the circumferential maximum widths MW2 is equal to or greater than 50 mm. In this embodiment, the sum of the circumferential maximum widths MW2 is 50.8 mm. However, the sum of the circumferential maximum widths MW2 is not limited to this embodiment. As seen in FIG. 29 , at least one inner spline tooth 64 has an inner spline top diameter DM21. At least one inner spline tooth 64 has an inner spline tooth root circle RC22, and the inner spline tooth root circle RC22 has the inner spline top diameter DM21. However, the inner spline tooth root circle RC22 may have another diameter different from the inner spline top diameter DM21. The inner spline top diameter DM21 is equal to or less than 30 mm. The inner spline top diameter DM21 is equal to or greater than 25 mm. The inner spline top diameter DM21 is equal to or greater than 29 mm. In this embodiment, the inner spline top diameter DM21 is 29.6 mm. However, the inner spline top diameter DM21 is not limited to this embodiment and the above range. In this embodiment, the ratio of the inner spline top diameter DM21 to the tooth tip diameter TD1 is in the range of 0.1 to 0.2. The tooth tip diameter TD1 of the largest sprocket SP12 (Figure 1) is in the range of 183.7 mm to 207.9 mm. The ratio of the inner spline top diameter DM21 to the tooth tip diameter TD1 is in the range of 0.14 to 0.17. However, the ratio of the inner spline top diameter DM21 to the tooth tip diameter TD1 is not limited to the above range. At least one inner spline tooth 64 has an inner spline bottom diameter DM22 equal to or less than 28 mm. The inner spline bottom diameter DM22 is equal to or greater than 25 mm. The inner spline bottom diameter DM22 is equal to or greater than 27 mm. In this embodiment, the inner spline bottom diameter DM22 is 27.7 mm. However, the inner spline bottom diameter DM22 is not limited to this embodiment and the above range. As seen in Figure 28, the plurality of inner spline transmission surfaces 66 include a radial outermost edge 66A and a radial innermost edge 66B. The plurality of inner spline transmission surfaces 66 each include a radial length RL21 defined from the radial outermost edge 66A to the radial innermost edge 66B. The sum of the radial lengths RL21 of the plurality of inner spline transmission surfaces 66 is equal to or greater than 7 mm. The sum of the radial lengths RL21 is equal to or greater than 10 mm. The sum of the radial lengths RL21 is equal to or greater than 15 mm. In this embodiment, the sum of the radial lengths RL21 is 19.5 mm. However, the sum of the radial lengths RL21 is not limited to this embodiment and the above range. The plurality of internal spline teeth 64 have an additional radial length RL22. The additional radial lengths RL22 are defined from the internal spline tooth root circle RC22 to the radial innermost ends 64A of the plurality of internal spline teeth 64. The sum of the additional radial lengths RL22 is equal to or greater than 12 mm. In this embodiment, the sum of the additional radial lengths RL22 is 27.95 mm. However, the sum of the additional radial lengths RL22 is not limited to this embodiment and the above range. At least one of the inner spline teeth 64 has an asymmetric shape relative to the circumferential tooth tip center line CL2. The circumferential tooth tip center line CL2 is a line connecting the rotation center axis A1 and the circumferential center point CP2 of the radial innermost end 64A of the inner spline tooth 64. However, at least one of the inner spline teeth 64 may have a symmetric shape relative to the circumferential tooth tip center line CL2. At least one of the inner spline teeth 64 includes an inner spline driving surface 66 and an inner spline non-driving surface 68. The inner spline driving surface 66 has a first inner spline surface angle AG21. The first inner spline surface angle AG21 is defined between the inner spline transmission surface 66 and the first radial line L21. The first radial line L21 extends from the rotational center axis A1 of the bicycle rear sprocket assembly 14 to the radial outermost edge 66A of the inner spline transmission surface 66. The first inner pitch angle PA21 or the second inner pitch angle PA22 is defined between adjacent first radial lines L21 (see, for example, FIG. 26). The inner spline non-transmission surface 68 has a second inner spline surface angle AG22. The second inner spline surface angle AG22 is defined between the inner spline non-transmission surface 68 and the second radial line L22. The second radial line L22 extends from the rotational center axis A1 of the bicycle rear sprocket assembly 14 to the radial outermost edge 68A of the inner spline non-driving surface 68. In this embodiment, the second inner spline surface angle AG22 is different from the first inner spline surface angle AG21. The first inner spline surface angle AG21 is less than the second inner spline surface angle AG22. However, the first inner spline surface angle AG21 may be equal to or greater than the second inner spline surface angle AG22. The first inner spline surface angle AG21 is in the range of 0 to 10 degrees. The second inner spline surface angle AG22 is in the range of 0 to 60 degrees. In this embodiment, the first inner spline surface angle AG21 is 5 degrees. The second inner spline surface angle AG22 is 45 degrees. However, the first inner spline surface angle AG21 and the second inner spline surface angle AG22 are not limited to this embodiment and the above range. As seen in FIG. 30 , the inner spline teeth 64 are engaged with the outer spline teeth 40 to transmit the transmission rotational force F1 from the sprocket SP1 to the sprocket support body 28. The inner spline transmission surface 66 can contact the outer spline transmission surface 48 to transmit the transmission rotational force F1 from the sprocket SP1 to the sprocket support body 28. In a state where the inner spline transmission surface 66 contacts the outer spline transmission surface 48, the inner spline non-transmission surface 68 is spaced apart from the outer spline non-transmission surface 50. As seen in FIG. 31 , sprocket SP2 includes a plurality of internal spline teeth 70. Sprocket SP3 includes a plurality of internal spline teeth 72. Sprocket SP4 includes a plurality of internal spline teeth 74. First ring 59A includes a plurality of internal spline teeth 76. As seen in FIG. 32 , hub engaging portion 60 of sprocket support 56 includes a plurality of internal spline teeth 78. The plurality of internal spline teeth 70 have a structure substantially the same as that of the plurality of internal spline teeth 64. The plurality of internal spline teeth 72 have a structure substantially the same as that of the plurality of internal spline teeth 64. The plurality of internal spline teeth 74 have a structure substantially the same as the structure of the plurality of internal spline teeth 64. The plurality of internal spline teeth 76 have a structure substantially the same as the structure of the plurality of internal spline teeth 64. The plurality of internal spline teeth 78 have a structure substantially the same as the structure of the plurality of internal spline teeth 64. Therefore, for the sake of brevity, they will not be described in detail herein. As seen in FIG. 6 , the bicycle rear sprocket assembly 14 further includes a rear wheel hub abutting surface 80. The rear wheel hub abutting surface 80 is configured to abut the bicycle wheel hub assembly 12 in the axial direction D2 relative to the rotation center axis A1 of the bicycle rear sprocket assembly 14 in a state where the bicycle rear sprocket assembly 14 is mounted to the bicycle wheel hub assembly 12. In this embodiment, the rear wheel hub abutting surface 80 abuts the larger diameter portion 42 of the sprocket support body 28 in the axial direction D2. The rear wheel hub abutting surface 80 is provided on the wheel hub engaging portion 60 of the sprocket support member 56. However, the position of the rear wheel hub abutting surface 80 is not limited to this embodiment. The largest sprocket SP12 has an axial inner surface SP12C and an axial outer surface SP12D disposed on the opposite side of the axial inner surface SP12C in the axial direction D2 relative to the rotation center axis A1 of the bicycle rear sprocket assembly 14. The axial outer surface SP12D is closer to the rear wheel hub adjacent surface 80 in the axial direction D2 than the axial inner surface SP12C. As seen in FIG. 15 , the bicycle wheel hub assembly 12 has an axial center plane CPL that bisects the bicycle wheel hub assembly 12 in the axial direction D2. The axial center plane CPL of the bicycle wheel hub assembly 12 is perpendicular to the rotation center axis A1. As seen in FIG. 6 , in a state where the bicycle rear sprocket assembly 14 is mounted to the bicycle rear wheel hub assembly 12 , the axial inner surface SP12C is positioned closer to the axial center plane CPL of the bicycle rear wheel hub assembly 12 than the rear wheel hub adjacent surface 80. An axial distance AD1 defined between the axial inner surface SP12C and the rear wheel hub adjacent surface 80 in the axial direction D2 is equal to or greater than 7 mm. The axial distance AD1 is equal to or greater than 10 mm. However, the axial distance AD1 is not limited to the above range. As seen in FIGS. 9 and 10 , the sprocket support body 28 includes a wheel hub indicator 28I disposed at an axial end of the base support member 41 . When viewed along the rotation center axis A1, the wheel hub indicator 28I is disposed in the region of the second outer pitch angle PA12. In this embodiment, the wheel hub indicator 28I includes a dot. However, the wheel hub indicator 28I may include other shapes, such as a triangle and a line. In addition, the wheel hub indicator 28I may be a separate component attached to the sprocket support body 28, for example, by an adhesive structure such as an adhesive. The position of the wheel hub indicator 28I is not limited to this embodiment. As seen in Figures 26 and 27, the sprocket SP1 includes a sprocket indicator SP1I disposed at an axial end of the sprocket body SP1A. When viewed along the rotation center axis A1, the sprocket indicator SP1I is disposed in the region of the second inner pitch angle PA22. In this embodiment, the sprocket indicator SP1I includes a dot. However, the sprocket indicator SP1I may include other shapes, such as a triangle and a line. In addition, the sprocket indicator SP1I may be a separate component attached to the sprocket SP1, for example, by an adhesive structure such as an adhesive. The position of the sprocket indicator SP1I is not limited to this embodiment. The sprocket indicator SP1I may be provided to any one of the other sprockets SP2 to SP12. The sprocket indicator SP1I may also be provided to the sprocket support member 56. Modification Figure 33 illustrates a bicycle rear sprocket assembly 214 according to a modification of the bicycle rear sprocket assembly 14. As seen in Figure 33, the bicycle rear sprocket assembly 214 includes a sprocket SP1 and a plurality of sprockets SP202 to SP212. The sprockets SP202 to SP212 have substantially the same structure as the sprockets SP2 to SP12. As shown in FIG. 33 and FIG. 34, for example, the sprocket SP212 includes a sprocket body SP12A and a plurality of sprocket teeth SP12B. One of the sprockets SP202 to SP212 may also be referred to as a first sprocket. Another sprocket adjacent to the first sprocket may also be referred to as a second sprocket. That is, at least one sprocket of the bicycle rear sprocket assembly 214 includes a first sprocket and a second sprocket. The first sprocket has a first total number of teeth. The second sprocket has a second total number of teeth less than the first total number of teeth. The second sprocket is adjacent to the first sprocket in the axial direction D2, and there is no other sprocket between the first sprocket and the second sprocket. As shown in FIG. 33 , for example, the first sprocket SP212 has a first total number of teeth of 51. The second sprocket SP211 has a second total number of teeth of 45. The sprockets SP212 and SP211 may also be referred to as the first sprocket SP212 and the second sprocket SP211. The sprockets SP211 and SP210 may also be referred to as the first sprocket SP211 and the second sprocket SP210. The sprockets SP210 and SP209 may also be referred to as the first sprocket SP210 and the second sprocket SP209. Sprockets SP209 and SP208 may also be referred to as first sprocket SP209 and second sprocket SP208. Sprockets SP208 and SP207 may also be referred to as first sprocket SP208 and second sprocket SP207. Sprockets SP207 and SP206 may also be referred to as first sprocket SP207 and second sprocket SP206. Sprockets SP206 and SP205 may also be referred to as first sprocket SP206 and second sprocket SP205. Sprockets SP205 and SP204 may also be referred to as first sprocket SP205 and second sprocket SP204. Sprockets SP204 and SP203 may also be referred to as first sprocket SP204 and second sprocket SP203. The sprockets SP203 and SP202 may also be referred to as the first sprocket SP203 and the second sprocket SP202. The sprockets SP202 and SP1 may also be referred to as the first sprocket SP202 and the second sprocket SP1. As seen in FIG. 34, for example, the first sprocket SP212 includes at least one first shift facilitating region SP212X to facilitate a first shifting operation of the bicycle chain 20 from the second sprocket SP211 to the first sprocket SP212. The first sprocket SP212 includes at least one second shift facilitating region SP212Y to facilitate a second shifting operation of the bicycle chain 20 from the first sprocket SP212 to the second sprocket SP211. In this embodiment, the first sprocket SP212 includes a plurality of first shift promoting areas SP212X to promote a first shifting operation of the bicycle chain 20 from the second sprocket SP211 to the first sprocket SP212. The first sprocket SP212 includes a plurality of second shift promoting areas SP212Y to promote a second shifting operation of the bicycle chain 20 from the first sprocket SP212 to the second sprocket SP211. The first sprocket SP212 includes a plurality of first shift promoting grooves SP212X1 and a plurality of second shift promoting grooves SP212Y1. The first shift promoting grooves SP212X1 are disposed in the first shift promoting areas SP212X. The second shift promoting grooves SP212Y1 are disposed in the second shift promoting areas SP212Y. As seen in FIG35, a first shift facilitating groove SP212X1 is provided on the axial outer surface SP12D to reduce interference between the first sprocket SP212 and the bicycle chain 20 (FIG33) in a first shifting operation. A second shift facilitating groove SP212Y1 is provided on the axial outer surface SP12D to reduce interference between the first sprocket SP212 and the bicycle chain 20 (FIG33) in a second shifting operation. The second shift facilitating groove SP212Y1 is spaced apart from the first shift facilitating groove SP212X1 in a circumferential direction D1. As seen in FIG36, a plurality of sprocket teeth SP12B of the first sprocket SP212 include a plurality of shift facilitating teeth SP212B1 to SP212B3. The shift promoting teeth SP212B1 to SP212B3 are arranged in the second shift promoting area SP212Y. As seen in FIG. 34, the second shift promoting area SP212Y is defined in the circumferential direction D1 by the second shift promoting groove SP212Y1 and the shift promoting teeth SP212B3. As seen in FIG. 37, the shift promoting teeth SP212B1 include the promoting groove SP212R1. The shift promoting teeth SP212B2 include the promoting groove SP212R2. The shift promoting teeth SP212B3 include the promoting groove SP212R3. The promoting groove SP212R1 is arranged on the axial inner surface SP12C to promote the derailment of the bicycle chain 20 from the first sprocket SP212 in the second shifting operation. The promotion groove SP212R2 is provided on the axial inner surface SP12C to promote the derailment of the bicycle chain 20 from the first sprocket SP212 in the second shifting operation. The promotion groove SP212R3 is provided on the axial inner surface SP12C to promote the derailment of the bicycle chain 20 from the first sprocket SP212 in the second shifting operation. The first shift promotion area and the second shift promotion area of each of the sprockets SP202 to SP211 have substantially the same structure as the first shift promotion area SP212X and the second shift promotion area SP212Y of the first sprocket SP212, respectively. For the sake of brevity, they will not be described in detail here. As used herein, the term "shift facilitating region" is intended to be an area that is intentionally designed to facilitate the shifting operation of a bicycle chain from one sprocket to another axially adjacent sprocket in the area. As seen in FIG. 38 , in the above-described embodiment, the external spline teeth 40 may include a groove 40G disposed between the external spline driving surface 48 and the external spline non-driving surface 50 in the circumferential direction D1. The groove 40G reduces the weight of the bicycle wheel hub assembly 12. As seen in FIG. 39 , in the above-described embodiment, the internal spline teeth 64 may include a groove 64G disposed between the internal spline driving surface 66 and the internal spline non-driving surface 68 in the circumferential direction D1. The groove 64G reduces the weight of the bicycle rear sprocket assembly 14. As used herein, the term "comprising" and its derivatives are intended to be open terms that specify the existence of stated features, elements, components, groups, integers and/or steps but do not exclude the existence of other unstated features, elements, components, groups, integers and/or steps. This concept also applies to words of similar meanings, such as the terms "having", "including" and their derivatives. The terms "component", "section", "part", "component", "element", "body" and "structure" when used in the singular can have dual meanings of a single component or a plurality of components. The ordinal numbers such as "first" and "second" described in this application are merely identifiers and do not have any other meanings, such as a specific order and the like. In addition, for example, the term "first element" itself does not imply the existence of a "second element", and the term "second element" itself does not imply the existence of a "first element". The term "pair" as used herein can cover configurations in which paired elements have shapes or structures that are different from each other, except configurations in which paired elements have shapes or structures that are the same as each other. Therefore, the terms "one", "one or more" and "at least one" can be used interchangeably herein. Finally, degree terms such as "substantially", "approximately" and "roughly" as used herein mean a reasonable amount of deviation of the modified term so that the final result is not significantly changed. All numerical values described in this application can be understood to include terms such as "substantially", "approximately" and "roughly". Obviously, in view of the above teachings, many modifications and variations of the present invention are possible. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced other than as specifically described herein.

10: Bicycle transmission system 12: Bicycle wheel hub assembly 14: Bicycle rear sprocket assembly 16: Bicycle brake rotor 18: Crank assembly 20: Bicycle chain 22: Crank axle 24: Right crank arm 26: Left crank arm 27: Front sprocket 28: Sprocket support body 28A: Internal threaded portion 30: Wheel hub axle 30A: Through hole 30B: First shaft end 30B1: Axial contact surface 30C: Second shaft end 32: Locking member 32A: External threaded portion 32B: Protruding portion 32C: Tubular body portion 32C1: Inner peripheral surface 32D: Tool engaging portion 32D1: Tool engaging groove 34: Brake rotor support body 36: Hub body 36A: First flange 36B: Second flange 38: Ratchet structure/one-way coupling structure 39A: First bearing 39B: Second bearing 40: External spline teeth 40A: Radial outermost end 40G: Groove 41: Base support 42: Larger diameter portion 42A: Axial end 44: Flange 46: Spiral external spline teeth 48: External spline transmission surface 48A: radial outermost edge 48B: radial innermost edge 50: external spline non-driving surface 50A: radial outermost edge 50B: radial innermost edge 50R: reference point 52: additional external spline teeth 54: additional base support 56: sprocket support 58: spacers 58A: first spacer 58B: second spacer 58C: third spacer 58D: fourth spacer 58E: fifth spacer 58F: sixth spacer 58G: seventh spacer 59A: first ring 59B: second ring 60: hub engagement portion 62: Support arm 62A: First attachment portion 62B: Second attachment portion 62C: Third attachment portion 62D: Fourth attachment portion 62E: Fifth attachment portion 62F: Sixth attachment portion 62G: Seventh attachment portion 62H: Eighth attachment portion 64: Internal spline teeth 64A: Radial innermost end 64G: Groove 66: Internal spline driving surface 66A: Radial outermost edge 66B: Radial innermost edge 68: Internal spline non-driving surface 68A: Radial outermost edge 68B: Radial innermost edge 68R: Reference point 70: Internal spline teeth 72: Inner spline teeth 74: Inner spline teeth 76: Inner spline teeth 78: Inner spline teeth 80: Rear wheel hub adjacent surface 214: Bicycle rear sprocket assembly A1: Rotation center axis A2: Center axis AD1: Axial distance AG11: First outer spline surface angle AG12: Second outer spline surface angle AG21: First inner spline surface angle AG22: Second inner spline surface angle AL11: First axial length AL12: Second axial length AL13: Axial length BF: Bicycle frame BF1: First frame BF2: Second frame BF11: First groove BF12: Frame contact surface BF21: Second groove CL1: Circumferential tooth tip centerline CL2: Circumferential tooth tip centerline CP1: Circumferential center point CP2: Circumferential center point CPL: Axial center plane D1: Circumferential direction D2: Axial direction D11: Transmission rotation direction D12: Reverse rotation direction DM11: External spline top diameter DM12: External spline bottom diameter DM13: Outer diameter DM14: Additional external spline top diameter DM21: Internal spline top diameter DM22: Internal spline bottom diameter ED1: First outer diameter ED2: Second outer diameter F1: Transmission rotation force F2: Thrust F3: Thrust IV-IV: Line L11: First radial line L12: Second radial line L21: First radial line L22: Second radial line MW1: Maximum circumferential width MW2: Maximum circumferential width PA11: First external pitch angle PA12: Second external pitch angle PA21: First internal pitch angle PA22: Second internal pitch angle RC11: First reference circle RC12: External spline tooth root circle RC21: Second reference circle RC22: Internal spline tooth root circle RL11: Radial length RL12: Radial length RL21: Radial length RL22: Additional radial length SP1: Sprocket SP1A: Sprocket body SP1B: sprocket gear SP2: sprocket SP2A: sprocket body SP2B: sprocket gear SP3: sprocket SP3A: sprocket body SP3B: sprocket gear SP4: sprocket SP4A: sprocket body SP4B: sprocket gear SP5: sprocket SP5A: sprocket body SP5B: sprocket gear SP6: sprocket SP6A: sprocket body SP6B: sprocket gear SP7: sprocket SP7A: sprocket body SP7B: sprocket gear SP8: sprocket SP8A: sprocket body SP8B: sprocket gear SP9: sprocket SP9A: Sprocket body SP9B: Sprocket gear SP10: Sprocket SP10A: Sprocket body SP10B: Sprocket gear SP11: Sprocket SP11A: Sprocket body SP11B: Sprocket gear SP12: Sprocket SP12A: Sprocket body SP12B: Sprocket gear SP12C: Axial inner surface SP12D: Axial outer surface SP202: Sprocket SP203: Sprocket SP204: Sprocket SP205: Sprocket SP206: Sprocket SP207: Sprocket SP208: Sprocket SP209: Sprocket SP210: Sprocket SP211: sprocket SP212: sprocket SP212B1: shift-promoting teeth SP212B2: shift-promoting teeth SP212B3: shift-promoting teeth SP212R1: promoting groove SP212R2: promoting groove SP212R3: promoting groove SP212X: first shift-promoting area SP212X1: first shift-promoting groove SP212Y: second shift-promoting area SP212Y1: second shift-promoting groove TD1: tooth tip diameter WS: wheel fastening structure WS1: fastening rod XVI-XVI: line XXIII-XXIII: line

A more complete appreciation of the present invention and its many attendant advantages will be readily obtained and likewise become better understood with reference to the following detailed description when considered in conjunction with the accompanying drawings, wherein: FIG. 1 is a schematic diagram of a bicycle transmission system according to one embodiment. FIG. 2 is an exploded perspective view of the bicycle transmission system illustrated in FIG. 1 . FIG. 3 is another perspective view of the bicycle transmission system illustrated in FIG. 2 . FIG. 4 is a cross-sectional view of the bicycle transmission system taken along line IV-IV of FIG. 2 . FIG. 5 is an exploded perspective view of a bicycle wheel hub assembly of the bicycle transmission system illustrated in FIG. 2 . FIG. 6 is an enlarged cross-sectional view of the bicycle transmission system illustrated in FIG. 4 . FIG. 7 is a perspective view of the sprocket support body of the bicycle wheel hub assembly of the bicycle transmission system illustrated in FIG. 2. FIG. 8 is another perspective view of the sprocket support body of the bicycle wheel hub assembly of the bicycle transmission system illustrated in FIG. 2. FIG. 9 is a side view of the sprocket support body illustrated in FIG. 7. FIG. 10 is a side view of the sprocket support body of the bicycle wheel hub assembly according to the modification. FIG. 11 is an enlarged cross-sectional view of the sprocket support body illustrated in FIG. 7. FIG. 12 is a cross-sectional view of the sprocket support body illustrated in FIG. 7. FIG. 13 is a perspective view of the bicycle wheel hub assembly of the bicycle transmission system illustrated in FIG. 2. FIG. 14 is a side view of the bicycle wheel hub assembly of the bicycle transmission system illustrated in FIG. 2. FIG. 15 is a rear view of the bicycle wheel hub assembly of the bicycle transmission system illustrated in FIG. 2. FIG. 16 is a cross-sectional view of the bicycle wheel hub assembly taken along line XVI-XVI of FIG. 5. FIG. 17 is a side view of the bicycle rear sprocket assembly of the bicycle transmission system illustrated in FIG. 2. FIG. 18 is an exploded perspective view of the bicycle rear sprocket assembly illustrated in FIG. 17. FIG. 19 is a partially exploded perspective view of the bicycle rear sprocket assembly illustrated in FIG. 17. FIG. 20 is another partially exploded perspective view of the bicycle rear sprocket assembly illustrated in FIG. 17. FIG. 21 is another partially exploded perspective view of the bicycle rear sprocket assembly illustrated in FIG. 17. FIG. 22 is another partially exploded perspective view of the bicycle rear sprocket assembly illustrated in FIG. 17. FIG. 23 is a perspective cross-sectional view of the bicycle rear sprocket assembly taken along line XXIII-XXIII of FIG. 17. FIG. 24 is a perspective view of the smallest sprocket of the bicycle rear sprocket assembly illustrated in FIG. 17. FIG. 25 is another perspective view of the smallest sprocket of the bicycle rear sprocket assembly illustrated in FIG. 17. FIG. 26 is a side view of the smallest sprocket of the bicycle rear sprocket assembly illustrated in FIG. 17. FIG. 27 is a side view of the smallest sprocket according to the modification. FIG. 28 is an enlarged cross-sectional view of the smallest sprocket illustrated in FIG. 24. FIG. 29 is a cross-sectional view of the smallest sprocket illustrated in FIG. 24. FIG. 30 is a cross-sectional view of the sprocket support body and the smallest sprocket of the bicycle transmission system illustrated in FIG. 2. FIG. 31 is a partially exploded perspective view of the bicycle rear sprocket assembly illustrated in FIG. 17. FIG. 32 is a perspective view of the sprocket support member of the bicycle rear sprocket assembly illustrated in FIG. 17. FIG. 33 is a side view of the bicycle rear sprocket assembly according to the modification. FIG. 34 is a side view of the first sprocket of the bicycle rear sprocket assembly illustrated in FIG. 33. FIG. 35 is a partial perspective view of the first sprocket of the bicycle rear sprocket assembly illustrated in FIG. 33. FIG. 36 is another side view of the first sprocket of the bicycle rear sprocket assembly illustrated in FIG. 33. FIG. 37 is another partial perspective view of the first sprocket of the bicycle rear sprocket assembly illustrated in FIG. 33. FIG. 38 is an enlarged cross-sectional view of the modified sprocket support body. FIG. 39 is an enlarged cross-sectional view of the modified smallest sprocket.

14: Bicycle rear sprocket assembly

20: Bicycle chain

A1: Rotation center axis

D1: Circumferential direction

D11: Transmission rotation direction

D12: Reverse rotation direction

SP1: sprocket

SP1B: sprocket gear

SP2: sprocket

SP2B: sprocket gear

SP3: Sprocket

SP3B: sprocket gear

SP4: sprocket

SP4B: sprocket gear

SP5: Chain wheel

SPSB: sprocket gear

SP6: Sprocket

SP6B: sprocket gear

SP7: sprocket

SP7B: sprocket gear

SP8: sprocket

SP8B: sprocket teeth

SP9: sprocket

SP9B: sprocket gear

SP10: Sprocket

SP10B: sprocket gear

SP11: Sprocket

SP11B: sprocket gear

SP12: Sprocket

SP12B: sprocket gear

TD1: Tooth tip diameter

XXIII-XXIII: Line

Claims (10)

A bicycle rear sprocket assembly, comprising: a plurality of sprockets, each of which includes at least ten internal spline teeth configured to engage with a bicycle hub assembly; the at least ten internal spline teeth including a plurality of internal spline transmission surfaces for transmitting rotational force to a sprocket support body of the bicycle hub assembly during pedaling; Each of the plurality of internal spline drive surfaces comprises: a radial outermost edge, a radial innermost edge, and a radial length defined from the radial outermost edge to the radial innermost edge, and; a sum of the radial lengths of the plurality of internal spline drive surfaces of the at least ten internal spline teeth is equal to or greater than 7 mm; the at least ten internal spline teeth are At least one of the inner spline teeth includes: an inner spline transmission surface having an inner spline surface angle defined between the inner spline transmission surface and a radial line extending from a rotational center axis of the bicycle rear sprocket assembly to a radial outermost edge of the inner spline transmission surface; the inner spline surface angle is in the range of 0 degrees to 10 degrees; wherein the plurality of sprockets include: a first sprocket having a first total number of teeth; and a second sprocket having a second total number of teeth less than the first total number of teeth; and wherein the first sprocket includes at least a first shift facilitating region to facilitate a first shifting operation of a bicycle chain from the second sprocket to the first sprocket. A bicycle rear sprocket assembly as claimed in claim 1, wherein the total number of one of the at least ten internal spline teeth is equal to or greater than 20. A bicycle rear sprocket assembly as claimed in claim 1, wherein the first sprocket includes at least one second shifting facilitating region to facilitate a second shifting operation of the bicycle chain from the first sprocket to the second sprocket. A bicycle rear sprocket assembly as claimed in claim 1, wherein the at least ten inner spline teeth have a first inner pitch angle and a second inner pitch angle different from the first inner pitch angle. A bicycle rear sprocket assembly as claimed in claim 1, further comprising a locking member configured to prevent the plurality of sprockets mounted on the bicycle wheel hub assembly from axially moving relative to the rotational center axis of the bicycle rear sprocket assembly, wherein the locking member comprises: a tubular main body portion having a center axis; and a protruding portion extending radially outward from the tubular main body portion relative to the center axis of the tubular main body portion, the tubular main body portion having an external threaded portion configured to engage with an internal threaded portion of the bicycle wheel hub assembly, and the protruding portion is configured to abut against one of the plurality of sprockets. A bicycle rear sprocket assembly as claimed in claim 5, wherein the locking member has a tool engaging portion. The bicycle rear sprocket assembly as claimed in claim 1 further comprises a sprocket support member, the plurality of sprockets being attached to the sprocket support member. The bicycle rear sprocket assembly of claim 1 further comprises a rear wheel hub adjacent surface which is configured to be adjacent to the bicycle wheel hub assembly in an axial direction relative to the rotation center axis of the bicycle rear sprocket assembly when the bicycle rear sprocket assembly is mounted to the bicycle wheel hub assembly, wherein the plurality of sprockets include a largest sprocket, the largest sprocket The sprocket has an axial inner surface and an axial outer surface disposed on an opposite side of the axial inner surface in the axial direction. The axial outer surface is closer to the rear wheel hub adjacent surface in the axial direction than the axial inner surface, and an axial distance defined between the axial inner surface and the rear wheel hub adjacent surface in the axial direction is equal to or greater than 7 mm. A bicycle rear sprocket assembly as claimed in claim 8, wherein the axial distance is equal to or greater than 10 mm. A bicycle rear sprocket assembly as claimed in claim 8, wherein in a state where the bicycle rear sprocket assembly is mounted to the bicycle wheel hub assembly, the axial inner surface is positioned closer to an axial center plane of the bicycle wheel hub assembly than the rear wheel hub adjacent surface.