Bicycle rear sprocket assembly

Abstract

The present invention provides a bicycle rear sprocket assembly comprising at least one sprocket and an inner cavity. The at least one sprocket includes at least ten internal splines configured to mesh with a bicycle hub assembly. The at least ten internal splines have an internal spline tip diameter. The inner cavity has a maximum outer diameter greater than one of the internal spline tip diameters.

Description

Rear Sprocket Assembly of Bicycle The present invention relates to a rear sprocket assembly of a bicycle. Cycling is becoming an increasingly popular form of recreation and 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 for competition, the bicycle industry is constantly improving various components of the bicycle. One bicycle component that has been fully redesigned is the sprocket assembly. According to a first aspect of the present invention, a rear sprocket assembly of a bicycle includes at least one sprocket and an inner cavity. The at least one sprocket includes at least ten internal spline teeth configured to engage with a bicycle hub assembly. The at least ten internal spline teeth have an internal spline pitch diameter. The inner cavity has a maximum outer diameter greater than the internal spline pitch diameter. In the case of the rear sprocket assembly of a bicycle according to the first aspect, compared with a sprocket including nine or fewer internal spline teeth, the at least ten internal spline teeth reduce the rotational force applied to each of the at least ten internal spline teeth. This improves the durability of the at least one sprocket and / or improves the freedom to select the material of the at least one sprocket without reducing the durability of the at least one sprocket. In addition, the inner cavity saves the weight of the rear sprocket assembly of the bicycle. According to a second aspect of the present invention, the rear sprocket assembly of a bicycle according to the first aspect is configured such that a total number of the at least ten internal spline teeth is equal to or greater than 20. In the case of the rear sprocket assembly of a bicycle according to the second aspect, compared with a sprocket including nine or fewer internal spline teeth, the at least twenty internal spline teeth further reduce the rotational force applied to each of the at least twenty internal spline teeth. This further improves the durability of the at least one sprocket and / or improves the freedom to select the material of the at least one sprocket without reducing the durability of the at least one sprocket. According to a third aspect of the present invention, the rear sprocket assembly of a bicycle according to the second aspect is configured such that the total number of the at least ten internal spline teeth is equal to or greater than 25. In the case of the rear sprocket assembly of a bicycle according to the third aspect, compared with a sprocket including nine or fewer internal spline teeth, the at least twenty-five internal spline teeth further reduce the rotational force applied to each of the at least twenty internal spline teeth. This further improves the durability of the at least one sprocket and / or improves the freedom to select the material of the at least one sprocket without reducing the durability of the at least one sprocket. According to a fourth aspect of the present invention, the rear sprocket assembly of a bicycle according to the first aspect is configured such that the at least ten internal spline teeth have a first internal pitch angle and a second internal pitch angle different from the first internal pitch angle. In the case of a bicycle rear sprocket assembly according to the fourth aspect, the difference between the first internal pitch angle and the second internal pitch angle helps the user to correctly install the bicycle rear sprocket assembly onto the bicycle hub assembly, particularly 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 according to the first aspect is configured such that at least one of the at least ten internal spline teeth has a first spline shape different from a second spline shape of another one of the at least ten internal spline teeth. In the case of a bicycle rear sprocket assembly according to the fifth aspect, the difference between the first spline shape and the second spline shape helps the user to correctly install the bicycle rear sprocket assembly onto the bicycle hub assembly, particularly with respect to the circumferential position of each sprocket of the bicycle rear sprocket assembly. According to a sixth aspect of the present invention, the bicycle rear sprocket assembly according to the first aspect is configured such that at least one of the at least ten internal spline teeth has a first spline size different from a second spline size of another one of the at least ten internal spline teeth. In the case of a bicycle rear sprocket assembly according to the sixth aspect, the difference between the first size and the second size helps the user to correctly install the bicycle rear sprocket assembly onto the sprocket support body, particularly with respect to the circumferential position of each sprocket of the bicycle rear sprocket assembly. According to a seventh aspect of the present invention, a bicycle rear sprocket assembly includes at least one sprocket and an inner cavity. The at least one sprocket includes a plurality of internal spline teeth configured to engage with a bicycle hub assembly. At least two of the plurality of internal spline teeth are circumferentially arranged along a first internal pitch angle with respect to a rotation central axis of the bicycle rear sprocket assembly. The first internal pitch angle is in the range of 10 degrees to 20 degrees. The plurality of internal spline teeth have an internal spline top diameter. The inner cavity has a maximum outer diameter greater than the internal spline top diameter. In the case of a bicycle rear sprocket assembly according to the seventh aspect, compared to a sprocket support body including nine or fewer internal spline teeth, the first internal pitch angle reduces the rotational force applied to each of the at least ten internal spline teeth. This improves the durability of at least one sprocket and / or improves the freedom to select the material of at least one sprocket without reducing the durability of at least one sprocket. In addition, the inner cavity saves the weight of the bicycle rear sprocket assembly. According to an eighth aspect of the present invention, the bicycle rear sprocket assembly according to the seventh aspect is configured such that the first internal pitch angle is in the range of 12 degrees to 15 degrees. In the case of the bicycle rear sprocket assembly according to the eighth aspect, compared to a sprocket support body including nine or fewer internal spline teeth, the first internal pitch angle further reduces the rotational force applied to each of at least ten internal spline teeth. This further improves the durability of at least one sprocket and / or improves the freedom in selecting the material of at least one sprocket without reducing the durability of at least one sprocket. According to a ninth aspect of the present invention, the bicycle rear sprocket assembly according to the eighth aspect is configured such that the first internal pitch angle is in the range of 13 degrees to 14 degrees. In the case of the bicycle rear sprocket assembly according to the ninth aspect, compared to a sprocket support body including nine or fewer internal spline teeth, the first internal pitch angle further reduces the rotational force applied to each of at least ten internal spline teeth. This further improves the durability of at least one sprocket and / or improves the freedom in selecting the material of at least one sprocket without reducing the durability of at least one sprocket. According to a tenth aspect of the present invention, the bicycle rear sprocket assembly according to the seventh aspect is configured such that at least two of the plurality of internal spline teeth are circumferentially arranged relative to the rotation center axis at a second internal pitch angle. The second internal pitch angle is different from the first internal pitch angle. In the case of the bicycle rear sprocket assembly according to the tenth aspect, the difference between the first internal pitch angle and the second internal pitch angle helps a user to correctly mount the bicycle rear sprocket assembly to a bicycle hub assembly, particularly regarding the circumferential position of each sprocket of the bicycle rear sprocket assembly. According to an eleventh aspect of the present invention, the bicycle rear sprocket assembly according to any one of the first aspect to the tenth aspect is configured such that the at least one sprocket includes a first sprocket. The first sprocket includes a first sprocket body and a plurality of first sprocket teeth radially extending outward from the first sprocket body relative to a rotation center axis of the bicycle rear sprocket assembly. The first sprocket includes the plurality of internal spline teeth radially extending inward from the first sprocket body. In the case of the bicycle rear sprocket assembly according to the eleventh aspect, the plurality of internal spline teeth of the first sprocket improve the torque transmission efficiency of the bicycle rear sprocket assembly. According to a twelfth aspect of the present invention, the bicycle rear sprocket assembly according to the eleventh aspect is configured such that the first sprocket has a pitch diameter greater than the maximum outer diameter of the inner cavity. In the case of the bicycle rear sprocket assembly according to the twelfth aspect, it is possible to use the first sprocket as a lower-speed gear in the bicycle rear sprocket assembly. According to a thirteenth aspect of the present invention, the bicycle rear sprocket assembly according to the twelfth aspect is configured such that the pitch diameter of the first sprocket is the largest pitch diameter in the bicycle rear sprocket assembly. In the case of the bicycle rear sprocket assembly according to the thirteenth aspect, it is possible to use the first sprocket as a low-speed gear in the bicycle rear sprocket assembly. According to a fourteenth aspect of the present invention, the bicycle rear sprocket assembly according to the eleventh aspect is configured such that the at least one sprocket includes a second sprocket. The second sprocket includes a second sprocket body and a plurality of second sprocket teeth extending radially outward from the second sprocket body relative to the rotational center axis. The inner cavity is provided radially inward from the second sprocket body. In the case of the bicycle rear sprocket assembly according to the fourteenth aspect, it is possible to use the radially inner region of the second sprocket as the inner cavity. According to a fifteenth aspect of the present invention, the bicycle rear sprocket assembly according to the fourteenth aspect is configured such that the first sprocket is a member separate from the second sprocket. In the case of the bicycle rear sprocket assembly according to the fifteenth aspect, it is possible to improve the degree of freedom of design of one of the first sprocket and the second sprocket. According to a sixteenth aspect of the present invention, the bicycle rear sprocket assembly according to the fifteenth aspect further includes a coupling member that couples the first sprocket to the second sprocket. In the case of the bicycle rear sprocket assembly according to the sixteenth aspect, it is possible to improve the coupling strength between the first sprocket and the second sprocket by the coupling member. This improves the strength of the bicycle rear sprocket assembly by saving the weight of the bicycle rear sprocket assembly. According to a seventeenth aspect of the present invention, the bicycle rear sprocket assembly according to the sixteenth aspect is configured such that the coupling member is integrally provided with at least one of the first sprocket and the second sprocket as a single-piece integral member. In the case of the bicycle rear sprocket assembly according to the seventeenth aspect, it is possible to easily manufacture the coupling member. According to an eighteenth aspect of the present invention, the bicycle rear sprocket assembly according to the seventeenth aspect is configured such that the coupling member includes at least one coupling pin. In the case of the bicycle rear sprocket assembly according to the eighteenth aspect, it is possible to easily manufacture the coupling member. According to a nineteenth aspect of the present invention, the bicycle rear sprocket assembly according to any one of the fourteenth aspect to the eighteenth aspect is configured such that the plurality of first sprocket teeth and the plurality of second sprocket teeth are integrally provided with each other as a single-piece integral member. In the case of the bicycle rear sprocket assembly according to the nineteenth aspect, it is possible to improve the coupling strength between the first sprocket and the second sprocket by the coupling member. This improves the strength of the bicycle rear sprocket assembly by saving the weight of the bicycle rear sprocket assembly. According to a twentieth aspect of the present invention, the bicycle rear sprocket assembly according to any one of the first aspect to the nineteenth aspect is configured such that the at least ten internal spline teeth have an internal spline root diameter. The maximum outer diameter of the inner cavity is greater than the internal spline root diameter. In the case of the bicycle rear sprocket assembly according to the twentieth aspect, it is possible to enlarge the inner cavity. According to a twenty-first aspect of the present invention, the bicycle rear sprocket assembly according to any one of the first aspect to the twentieth aspect is configured such that at least one of the at least one sprocket includes a sprocket body and a plurality of sprocket teeth extending radially outward from the sprocket body with respect to a rotational center axis of the bicycle rear sprocket assembly. The plurality of sprocket teeth includes at least one first tooth and at least one second tooth. The at least one first tooth has a first maximum axial width defined in the axial direction with respect to the rotational center axis. The at least one second tooth has a second maximum axial width defined in the axial direction. The first maximum axial width is greater than the second maximum axial width. In the case of the bicycle rear sprocket assembly according to the twenty-first aspect, the at least one first tooth improves the chain retention performance of the bicycle rear sprocket assembly. According to a twenty-second aspect of the present invention, a bicycle rear sprocket assembly includes at least one sprocket. The at least one sprocket includes at least ten internal spline teeth configured to engage with a bicycle hub assembly. The at least ten internal spline teeth have an internal spline tip diameter. At least one of the at least one sprocket includes a sprocket body and a plurality of sprocket teeth extending radially outward from the sprocket body with respect to a rotational center axis of the bicycle rear sprocket assembly. The plurality of sprocket teeth includes at least one first tooth and at least one second tooth. The at least one first tooth has a first maximum axial width defined in the axial direction with respect to the rotational center axis. The at least one second tooth has a second maximum axial width defined in the axial direction. The first maximum axial width is greater than the second maximum axial width. In the case of the bicycle rear sprocket assembly according to the twenty-second aspect, compared with a sprocket including nine or fewer internal spline teeth, the at least ten internal spline teeth reduce the rotational force applied to each of the at least ten internal spline teeth. This improves the durability of at least one sprocket and / or improves the freedom to select the material of at least one sprocket without reducing the durability of at least one sprocket. In addition, the at least one first tooth improves the chain retention performance of the bicycle rear sprocket assembly. According to a twenty-third aspect of the present invention, the bicycle rear sprocket assembly according to any one of the first aspect to the twenty-second aspect is configured such that the at least one sprocket includes a smallest sprocket, and the smallest sprocket includes at least one sprocket tooth. The total number of the at least one sprocket tooth of the smallest sprocket is equal to or less than 10. In the case of a bicycle rear sprocket assembly according to the twenty-third aspect, it is possible to widen the transmission ratio range of the bicycle rear sprocket assembly on the high-speed gear side. According to a twenty-fourth aspect of the present invention, a bicycle rear sprocket assembly according to any one of the first aspect to the twenty-third aspect is configured such that the at least one sprocket includes a largest sprocket, and the largest sprocket includes at least one sprocket tooth. The total number of the at least one sprocket tooth of the largest sprocket is equal to or greater than 46. In the case of a bicycle rear sprocket assembly according to the twenty-fourth aspect, it is possible to widen the transmission ratio range of the bicycle rear sprocket assembly on the low-speed gear side. According to a twenty-fifth aspect of the present invention, a bicycle rear sprocket assembly according to the twenty-fourth aspect is configured such that the total number of the at least one sprocket tooth of the largest sprocket is equal to or greater than 50. In the case of a bicycle rear sprocket assembly according to the twenty-fifth aspect, it is possible to further widen the transmission ratio range of the bicycle rear sprocket assembly on the low-speed gear side. According to a twenty-sixth aspect of the present invention, a bicycle rear sprocket assembly according to any one of the first aspect to the twenty-fifth aspect is configured such that the total number of at least one sprocket is equal to or greater than 11. In the case of a bicycle rear sprocket assembly according to the twenty-sixth aspect, it is possible to widen the entire transmission ratio range of the bicycle rear sprocket assembly. Embodiments will now be described with reference to the accompanying drawings, in which like reference numerals designate corresponding or identical elements in the various figures. First Embodiment Referring initially to FIG. 1, a bicycle drive system 10 includes a bicycle hub assembly 12 and a bicycle rear sprocket assembly 14 according to a first embodiment. The bicycle hub assembly 12 is fastened to a bicycle frame BF. The bicycle rear sprocket assembly 14 is mounted on the bicycle hub assembly 12. A bicycle brake rotor 16 is mounted on the bicycle hub assembly 12. The bicycle drive system 10 further includes a crank assembly 18 and a bicycle chain 20. The crank assembly 18 includes a crankshaft 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 crankshaft 22. The front sprocket 27 is fastened to at least one of the crankshaft 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 pedal force from the front sprocket 27 to the bicycle rear sprocket assembly 14. The crank assembly 18 includes a front sprocket 27 that is a single sprocket as 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 a front sprocket. In the present application, the following directional terms "front", "rear", "forward", "backward", "left", "right", "lateral", "upward" and "downward" and any other similar directional terms refer to those directions determined based on a user (e.g., a rider) sitting on a bicycle seat (not shown in the figures) and facing the handlebars (not shown in the figures). Accordingly, when used to describe the bicycle drive system 10, the bicycle hub assembly 12 or the bicycle rear sprocket assembly 14, these terms should be interpreted with respect to a bicycle equipped with the bicycle drive system 10, the bicycle hub assembly 12 or the bicycle rear sprocket assembly 14 as used in an upright riding position on a horizontal surface. As seen in FIG. 2, the bicycle hub assembly 12 and the bicycle rear sprocket assembly 14 have a rotational center axis A1. The bicycle rear sprocket assembly 14 is rotatably supported by the bicycle hub assembly 12 about the rotational 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 so as to transmit a driving 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 rotational center axis A1 in the driving rotational direction D11. The driving rotational direction D11 is defined along the circumferential direction D1 of the bicycle hub assembly 12 or the bicycle rear sprocket assembly 14. The reverse rotational direction D12 is the opposite direction of the driving rotational direction D11 and is defined along the circumferential direction D1. As seen in FIG. 2, the bicycle hub assembly 12 includes a sprocket support body 28. The bicycle rear sprocket assembly 14 is configured to be mounted to the sprocket support body 28 of the bicycle hub assembly 12. The bicycle rear sprocket assembly 14 is mounted on the sprocket support body 28 to transmit a driving rotational force F1 between the sprocket support body 28 and the bicycle rear sprocket assembly 14. The bicycle hub assembly 12 includes a hub shaft 30. The sprocket support body 28 is rotatably mounted on the hub shaft 30 about the rotational 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 the axial direction D2 parallel to the rotational center axis A1. As can be seen in FIG. 3, the bicycle hub assembly 12 is fastened to the bicycle frame BF by a wheel fastening structure WS. The hub shaft 30 includes a shaft through-hole 30A. The fastening rod WS1 of the wheel fastening structure WS extends through the shaft through-hole 30A of the hub shaft 30. The hub shaft 30 includes a first shaft end 30B and a second shaft end 30C. The hub shaft 30 extends between the first shaft end 30B and the second shaft end 30C along a rotation center axis A1. The first shaft end 30B is disposed in a first groove BF11 of a first frame BF1 of the bicycle frame BF. The second shaft end 30C is disposed in a second groove BF21 of a second frame BF2 of the bicycle frame BF. The hub shaft 30 is held 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 bicycle being applied for. Therefore, for the sake of brevity, it will not be described in detail here. As can be seen in FIGS. 3 and 4, the bicycle hub assembly 12 further includes a brake rotor support body 34. The brake rotor support body 34 is rotatably mounted on the hub shaft 30 about a rotation center axis A1. As can be seen in FIG. 3, the brake rotor support body 34 is coupled to the bicycle brake rotor 16 (FIG. 3) to transmit a braking rotational force from the bicycle brake rotor 16 to the brake rotor support body 34. The bicycle brake rotor 16 is fastened to the brake rotor support body 34 by a rotor locking member 35. As can be seen in FIG. 4, the bicycle hub assembly 12 includes a hub body 36. The hub body 36 is rotatably mounted on the hub shaft 30 about a rotation center axis A1 of the bicycle hub assembly 12. In this embodiment, the sprocket support body 28 is a member separated from the hub body 36. The brake rotor support body 34 is integrally provided with the hub body 36 as a single-piece integral member. However, the sprocket support body 28 may be integrally provided with the hub body 36. The brake rotor support body 34 may be a member separated from the hub body 36. For example, the hub body 36 is made of a metallic material including aluminum. As can be seen in FIG. 5, the bicycle rear sprocket assembly 14 includes at least one sprocket. The bicycle rear sprocket assembly 14 includes a plurality of bicycle sprockets SP1 to SP12. In this embodiment, at least one sprocket includes a first sprocket SP1. At least one sprocket includes a second sprocket SP2. In this embodiment, at least one sprocket further includes a third sprocket SP3 to a twelfth sprocket SP12. The first sprocket SP1 is a member separated from the second sprocket SP2. The second sprocket SP2 to the twelfth sprocket SP12 are integrally provided with each other as a one-piece integral member. However, at least one of the second sprocket SP2 to the twelfth sprocket SP12 may be a member separated from another of the second sprocket SP2 to the twelfth sprocket SP12. In this embodiment, the first sprocket SP1 to the twelfth SP12 are made of a metallic material such as aluminum, iron or titanium. However, at least one of the first sprocket SP1 to the twelfth sprocket SP12 may be made of a non-metallic material. For example, the total number of at least one of the sprockets is equal to or greater than 11. In this embodiment, the total number of sprockets is 12. However, the total number of sprockets is not limited to this embodiment. For example, the total number of sprockets may be equal to or greater than 13. In this embodiment, at least one sprocket includes a largest sprocket. At least one sprocket includes a smallest sprocket. The first sprocket SP1 may also be referred to as the largest sprocket SP1. The twelfth sprocket SP12 may also be referred to as the smallest sprocket SP12. The first sprocket SP1 corresponds to a low-speed gear in the bicycle rear sprocket assembly 14. The twelfth sprocket SP12 corresponds to a high-speed gear in the bicycle rear sprocket assembly 14. However, the first sprocket SP1 may correspond to another gear in the bicycle rear sprocket assembly 14. The twelfth sprocket SP12 may correspond to another gear in the bicycle rear sprocket assembly 14. As can be seen in FIG. 5, the first sprocket SP1 has a pitch circle diameter PCD1. The second sprocket SP2 has a pitch circle diameter PCD2. The third sprocket SP3 has a pitch circle diameter PCD3. The fourth sprocket SP4 has a pitch circle diameter PCD4. The fifth sprocket SP5 has a pitch circle diameter PCD5. The sixth sprocket SP6 has a pitch circle diameter PCD6. The seventh sprocket SP7 has a pitch circle diameter PCD7. The eighth sprocket SP8 has a pitch circle diameter PCD8. The ninth sprocket SP9 has a pitch circle diameter PCD9. The tenth sprocket SP10 has a pitch circle diameter PCD10. The eleventh sprocket SP11 has a pitch circle diameter PCD11. The twelfth sprocket SP12 has a pitch circle diameter PCD12. The first sprocket SP1 has a pitch circle PC1 with a pitch circle diameter PCD1. The second sprocket SP2 has a pitch circle PC2 with a pitch circle diameter PCD2. The third sprocket SP3 has a pitch circle PC3 with a pitch circle diameter PCD3. The fourth sprocket SP4 has a pitch circle PC4 with a pitch circle diameter PCD4. The fifth sprocket SP5 has a pitch circle PC5 with a pitch circle diameter PCD5. The sixth sprocket SP6 has a pitch circle PC6 with a pitch circle diameter PCD6. The seventh sprocket SP7 has a pitch circle PC7 with a pitch circle diameter PCD7. The eighth sprocket SP8 has a pitch circle PC8 with a pitch circle diameter PCD8. The ninth sprocket SP9 has a pitch circle PC9 with a pitch circle diameter PCD9. The tenth sprocket SP10 has a pitch circle PC10 with a pitch circle diameter PCD10. The eleventh sprocket SP11 has a pitch circle PC11 with a pitch circle diameter PCD11. The twelfth sprocket SP12 has a pitch circle PC12 with a pitch circle diameter PCD12. For example, the pitch circle PC1 of the first sprocket SP1 is defined by the central axes of the pins of the bicycle chain 20 (Figure 2) that meshes with the first sprocket SP1. The pitch circles PC2 to PC12 are defined in the same way as the pitch circle PC1. Therefore, for the sake of brevity, they will not be described in detail here. In this embodiment, the pitch circle diameter PCD1 is greater than the pitch circle diameter PCD2. The pitch circle diameter PCD2 is greater than the pitch circle diameter PCD3. The pitch circle diameter PCD3 is greater than the pitch circle diameter PCD4. The pitch circle diameter PCD4 is greater than the pitch circle diameter PCD5. The pitch circle diameter PCD5 is greater than the pitch circle diameter PCD6. The pitch circle diameter PCD6 is greater than the pitch circle diameter PCD7. The pitch circle diameter PCD7 is greater than the pitch circle diameter PCD8. The pitch circle diameter PCD8 is greater than the pitch circle diameter PCD9. The pitch circle diameter PCD9 is greater than the pitch circle diameter PCD10. The pitch circle diameter PCD10 is greater than the pitch circle diameter PCD11. The pitch circle diameter PCD11 is greater than the pitch circle diameter PCD12. The pitch circle diameter PCD1 of the first sprocket SP1 is the largest pitch circle diameter in the bicycle rear sprocket assembly 14. The pitch circle diameter PCD12 of the twelfth sprocket SP12 is the smallest pitch circle diameter in the bicycle rear sprocket assembly 14. However, the pitch circle diameter PCD1 of the first sprocket SP1 is not limited to being the largest pitch circle diameter in the bicycle rear sprocket assembly 14. The pitch circle diameter PCD12 of the twelfth sprocket SP12 is not limited to being the smallest pitch circle diameter in the bicycle rear sprocket assembly 14. As can be seen in FIG. 6, the second sprocket SP2 is adjacent to the first sprocket SP1 in the axial direction D2 with respect to the rotation center axis A1 of the bicycle rear sprocket assembly 14, and there is no other sprocket between the first sprocket SP1 and the second sprocket SP2. The third sprocket SP3 is adjacent to the second sprocket SP2 in the axial direction D2 with respect to the rotation center axis A1 of the bicycle rear sprocket assembly 14, and there is no other sprocket between the second sprocket SP2 and the third sprocket SP3. The fourth sprocket SP4 is adjacent to the third sprocket SP3 in the axial direction D2 with respect to the rotation center axis A1 of the bicycle rear sprocket assembly 14, and there is no other sprocket between the third sprocket SP3 and the fourth sprocket SP4. The first sprocket SP1 to the twelfth sprocket SP12 are arranged in this order in the axial direction D2. As can be seen in FIG. 7, at least one of the at least one sprocket includes a sprocket body and a plurality of sprocket teeth radially extending outward from the sprocket body with respect to the rotation center axis A1 of the bicycle rear sprocket assembly 14. The largest sprocket SP1 includes at least one sprocket tooth SP1B. The first sprocket SP1 includes a first sprocket body SP1A and a plurality of first sprocket teeth SP1B. The plurality of first sprocket teeth SP1B radially extend outward from the first sprocket body SP1A with respect to the rotation center axis A1 of the bicycle rear sprocket assembly 14. The first sprocket tooth SP1B can also be referred to as the sprocket tooth SP1B. The total number of at least one sprocket tooth SP1B of the largest sprocket SP1 is equal to or greater than 46. The total number of at least one sprocket tooth SP1B of the largest sprocket SP1 is equal to or greater than 50. In this embodiment, the total number of at least one sprocket tooth SP1B of the first sprocket SP1 is 51. However, the total number of the plurality of sprocket teeth SP1B of the first sprocket SP1 is not limited to this embodiment and the above range. The second sprocket SP2 includes a second sprocket body SP2A and a plurality of second sprocket teeth SP2B. The plurality of second sprocket teeth SP2B radially extend outward from the second sprocket body SP2A with respect to the rotation center axis A1. In this embodiment, the total number of the plurality of second sprocket teeth SP2B is 45. However, the total number of the plurality of second sprocket teeth SP2B of the second sprocket SP2 is not limited to this embodiment. The third sprocket SP3 includes a third sprocket body SP3A and a plurality of third sprocket teeth SP3B. The plurality of third sprocket teeth SP3B radially extend outward from the third sprocket body SP3A with respect to the rotation center axis A1 of the bicycle rear sprocket assembly 14. In this embodiment, the total number of the plurality of third sprocket teeth SP3B is 39. However, the total number of the plurality of third sprocket teeth SP3B of the third sprocket SP3 is not limited to this embodiment. The fourth sprocket SP4 includes a fourth sprocket body SP4A and a plurality of fourth sprocket teeth SP4B. The plurality of fourth sprocket teeth SP4B extend radially outward from the fourth sprocket body SP4A with respect to the rotation center axis A1 of the bicycle rear sprocket assembly 14. In this embodiment, the total number of the plurality of fourth sprocket teeth SP4B is 33. However, the total number of the plurality of fourth sprocket teeth SP4B of the fourth sprocket SP4 is not limited to this embodiment. The fifth sprocket SP5 includes a fifth sprocket body SP5A and a plurality of fifth sprocket teeth SP5B. The plurality of fifth sprocket teeth SP5B extend radially outward from the fifth sprocket body SP5A with respect to the rotation center axis A1 of the bicycle rear sprocket assembly 14. In this embodiment, the total number of the plurality of fifth sprocket teeth SP5B is 28. However, the total number of the plurality of fifth sprocket teeth SP5B of the fifth sprocket SP5 is not limited to this embodiment. The sixth sprocket SP6 includes a sixth sprocket body SP6A and a plurality of sixth sprocket teeth SP6B. The plurality of sixth sprocket teeth SP6B extend radially outward from the sixth sprocket body SP6A with respect to the rotation center axis A1 of the bicycle rear sprocket assembly 14. In this embodiment, the total number of the plurality of sixth sprocket teeth SP6B is 24. However, the total number of the plurality of sixth sprocket teeth SP6B of the sixth sprocket SP6 is not limited to this embodiment. The seventh sprocket SP7 includes a seventh sprocket body SP7A and a plurality of seventh sprocket teeth SP7B. The plurality of seventh sprocket teeth SP7B extend radially outward from the seventh sprocket body SP7A with respect to the rotation center axis A1 of the bicycle rear sprocket assembly 14. In this embodiment, the total number of the plurality of seventh sprocket teeth SP7B is 21. However, the total number of the plurality of seventh sprocket teeth SP7B of the seventh sprocket SP7 is not limited to this embodiment. The eighth sprocket SP8 includes an eighth sprocket body SP8A and a plurality of eighth sprocket teeth SP8B. The plurality of eighth sprocket teeth SP8B extend radially outward from the eighth sprocket body SP8A with respect to the rotation center axis A1 of the bicycle rear sprocket assembly 14. In this embodiment, the total number of the plurality of eighth sprocket teeth SP8B is 18. However, the total number of the plurality of eighth sprocket teeth SP8B of the eighth sprocket SP8 is not limited to this embodiment. The ninth sprocket SP9 includes a ninth sprocket body SP9A and a plurality of ninth sprocket teeth SP9B. The plurality of ninth sprocket teeth SP9B extend radially outward from the ninth sprocket body SP9A with respect to the rotation center axis A1 of the bicycle rear sprocket assembly 14. In this embodiment, the total number of the plurality of ninth sprocket teeth SP9B is 16. However, the total number of the plurality of ninth sprocket teeth SP9B of the ninth sprocket SP9 is not limited to this embodiment. The tenth sprocket SP10 includes a tenth sprocket body SP10A and a plurality of tenth sprocket teeth SP10B. The plurality of tenth sprocket teeth SP10B extend radially outward from the tenth sprocket body SP10A with respect to the rotation central axis A1 of the rear sprocket assembly 14 of the bicycle. In this embodiment, the total number of the plurality of tenth sprocket teeth SP10B is 14. However, the total number of the plurality of tenth sprocket teeth SP10B of the tenth sprocket SP10 is not limited to this embodiment. The eleventh sprocket SP11 includes an eleventh sprocket body SP11A and a plurality of eleventh sprocket teeth SP11B. The plurality of eleventh sprocket teeth SP11B extend radially outward from the eleventh sprocket body SP11A with respect to the rotation central axis A1 of the rear sprocket assembly 14 of the bicycle. In this embodiment, the total number of the plurality of eleventh sprocket teeth SP11B is 12. However, the total number of the plurality of eleventh sprocket teeth SP11B of the eleventh sprocket SP11 is not limited to this embodiment. The smallest sprocket SP12 includes at least one sprocket tooth SP12B. The twelfth sprocket SP12 includes a twelfth sprocket body SP12A and a plurality of twelfth sprocket teeth SP12B. The plurality of twelfth sprocket teeth SP12B extend radially outward from the twelfth sprocket body SP12A with respect to the rotation central axis A1 of the rear sprocket assembly 14 of the bicycle. The twelfth sprocket tooth SP12B can also be referred to as the sprocket tooth SP12B. The total number of at least one sprocket tooth SP12B of the smallest sprocket SP12 is equal to or less than 10. In this embodiment, the total number of at least one sprocket tooth SP12B is 10. However, the total number of at least one sprocket tooth SP12B of the twelfth sprocket SP12 is not limited to this embodiment. As can be seen in FIG. 6, the rear sprocket assembly 14 of the bicycle includes an inner cavity 38. The inner cavity 38 is provided radially inward from the second sprocket body SP2A. The inner cavity 38 is provided radially inward from the third sprocket body SP3A to the twelfth sprocket body SP12A. However, the position of the inner cavity 38 is not limited to this embodiment. The inner cavity 38 has a maximum outer diameter MD1. The pitch circle diameter PCD1 of the first sprocket SP1 is greater than the maximum outer diameter MD1 of the inner cavity 38. The pitch circle diameter PCD2 of the second sprocket SP2 is greater than the maximum outer diameter MD1 of the inner cavity 38. The pitch circle diameter PCD3 of the third sprocket SP3 is less than the maximum outer diameter MD1 of the inner cavity 38. However, the dimensional relationship between the maximum outer diameter MD1 of the inner cavity 38 and each of the pitch circle diameters PCD1 to PCD12 of the first sprocket SP1 to the twelfth sprocket SP12 is not limited to this embodiment. The bicycle rear sprocket assembly 14 further includes a coupling member CM1 that couples the first sprocket SP1 to the second sprocket SP2. The coupling member CM1 is integrally provided with at least one of the first sprocket SP1 and the second sprocket SP2 as a single-piece integral member. In this embodiment, the coupling member CM1 includes at least one coupling pin CM1A. The coupling member CM1 includes a plurality of coupling pins CM1A. However, the coupling member CM1 may include alternative coupling pins CM1A or another part in addition to the coupling pins CM1A. The coupling member CM1 may also be referred to as the first coupling member CM1. As can be seen in FIG. 8, at least a part of the coupling member CM1 may be integrally provided with the first sprocket SP1 as a single-piece integral member. At least a part of the coupling member CM1 may be a member separated from the second sprocket SP2. As can be seen in FIG. 9, the coupling member CM1 may be a member separated from the first sprocket SP1 and the second sprocket SP2. As can be seen in FIG. 10, the coupling member CM1 may be integrally provided with the first sprocket SP1 and the second sprocket SP2 as a single-piece integral member. In this embodiment, the plurality of first sprocket teeth SP1B and the plurality of second sprocket teeth SP2B are integrally provided with each other as a single-piece integral member. The first sprocket SP1 includes a cover member 14A attached to the first sprocket body SP1A to engage with the sprocket support body 28. The bicycle rear sprocket assembly 14 further includes a second coupling member CM2 that couples the second sprocket SP2 to the third sprocket SP3. The second coupling member CM2 extends between the second sprocket SP2 and the third sprocket SP3 in the axial direction D2. The second coupling member CM2 includes a plurality of second coupling portions circumferentially arranged around the rotation center axis A1. In this embodiment, the second coupling member CM2 is integrally provided with the second sprocket SP2 and the third sprocket SP3. However, at least a part of the second coupling member CM2 may be a member separated from at least one of the second sprocket SP2 and the third sprocket SP3. The bicycle rear sprocket assembly 14 further includes a third coupling member CM3 that couples the third sprocket SP3 to the fourth sprocket SP4. The bicycle rear sprocket assembly 14 further includes a fourth coupling member CM4 that couples the fourth sprocket SP4 to the fifth sprocket SP5. The bicycle rear sprocket assembly 14 further includes a fifth coupling member CM5 that couples the fifth sprocket SP5 to the sixth sprocket SP6. The bicycle rear sprocket assembly 14 further includes a sixth coupling member CM6 that couples the sixth sprocket SP6 to the seventh sprocket SP7. The bicycle rear sprocket assembly 14 further includes a seventh coupling member CM7 that couples the seventh sprocket SP7 to the eighth sprocket SP8. The bicycle rear sprocket assembly 14 further includes an eighth coupling member CM8 that couples the eighth sprocket SP8 to the ninth sprocket SP9. The bicycle rear sprocket assembly 14 further includes a ninth coupling member CM9 that couples the ninth sprocket SP9 to the tenth sprocket SP10. The bicycle rear sprocket assembly 14 further includes a tenth coupling member CM10 that couples the tenth sprocket SP10 to the eleventh sprocket SP11. The bicycle rear sprocket assembly 14 further includes an eleventh coupling member CM11 that couples the eleventh sprocket SP11 to the twelfth sprocket SP12. The third coupling member CM3 to the eleventh coupling member CM11 have substantially the same structure as the structure of the second coupling member CM2. Therefore, for the sake of brevity, it will not be described in detail here. In this embodiment, the first sprocket SP1 to the twelfth sprocket SP12 and the first coupling member CM1 to the eleventh coupling member CM11 define an inner cavity 38. The coupling member CM1 defines a maximum outer diameter MD1. The inner cavity 38 is disposed between the first sprocket SP1 and the twelfth sprocket SP12 in the axial direction D2. However, the inner cavity 38 is not limited to this embodiment. As seen in FIG. 4, the locking member 32 includes a tubular body 32A, an external thread portion 32B, and a radially protruding portion 32C. The tubular body 32A includes a first axial end 32D and a second axial end 32E. Relative to the rotation center axis A1 of the bicycle rear sprocket assembly 14, the second axial end 32E is opposite to the first axial end 32D in the axial direction D2. As seen in FIG. 6, in a state where the bicycle rear sprocket assembly 14 is mounted to the bicycle hub assembly 12, the first axial end 32D is positioned closer to the axial center plane CPL of the bicycle hub assembly 12 than the second axial end 32E. The axial center plane CPL is perpendicular to the rotation center axis A1. As seen in FIG. 3, the axial center plane CPL is defined to bisect the axial length of the bicycle hub assembly 12 in the axial direction D2. As shown in FIG. 6, an external thread portion 32B is provided at the first axial end 32D to be screwed with an internal thread portion 28A of a sprocket support body 28 of the bicycle hub assembly 12 when the rear sprocket assembly 14 of the bicycle is mounted to the bicycle hub assembly 12. A radial protrusion 32C extends outward in the radial direction from the second axial end 32E relative to the rotation center axis A1 to limit the axial movement of the first sprocket SP1 to the twelfth sprocket SP12 relative to the sprocket support body 28 of the bicycle hub assembly 12 when the rear sprocket assembly 14 of the bicycle is mounted to the bicycle hub assembly 12. The radial protrusion 32C is configured to abut against the twelfth sprocket SP12. As shown in FIG. 4, the locking member 32 has a tool engagement portion 32F. The tool engagement portion 32F is provided on an inner peripheral surface 32A1 of the tubular body 32A to engage with a fastening tool (not shown in the figure). In this embodiment, the tool engagement portion 32F includes a plurality of engagement grooves 32G, and the engagement grooves 32G will engage with the fastening tool when the locking member 32 is threadedly attached to the sprocket support body 28 by the external thread portion 32B and the internal thread portion 28A. The structure of the tool engagement portion 32F is not limited to this embodiment. For example, as shown in FIG. 11, the locking member 32 may have a tool engagement portion 132F. The tool engagement portion 132F is provided at the second axial end 32E. The tool engagement portion 132F includes an annular member 132F1 and a plurality of protrusions 132F2 extending outward in the radial direction from the annular member 132F1. The plurality of protrusions 132F2 are arranged in a circle at a constant interval. The plurality of protrusions 132F2 define a plurality of engagement grooves 132F3, and the engagement grooves 132F3 will engage with the fastening tool when the locking member 32 is threadedly attached to the sprocket support body 28 (FIG. 4) by the external thread portion 32B and the internal thread portion 28A (FIG. 4). As shown in FIGS. 12 and 13, the sprocket support body 28 includes at least one external spline tooth 40 configured to engage with the rear sprocket assembly 14 (FIG. 6) of the bicycle. The sprocket support body 28 includes at least ten external spline teeth 40 configured to engage with the rear sprocket assembly 14 (FIG. 6) of the bicycle. That is, at least one external spline tooth 40 includes a plurality of external spline teeth 40. 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 helical 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 helical external spline teeth 46 in the axial direction D2. As seen in FIG. 6, the rear sprocket assembly 14 of the bicycle is held in the axial direction D2 between the larger diameter portion 42 and the radially protruding portion 32C of the locking member 32. The larger diameter portion 42 may have an internal cavity such that a transmission structure such as a one-way coupling structure can be accommodated in the internal cavity. If necessary, the larger diameter portion 42 can be omitted from the bicycle hub assembly 12. As seen in FIG. 14, at least one of the at least ten external spline teeth 40 has an axial spline tooth length SL1. Each of the external spline teeth 40 has an axial spline tooth length SL1. The axial spline tooth length SL1 is equal to or less than 27 mm. The axial spline tooth length SL1 is equal to or greater than 22 mm. In this embodiment, the axial spline tooth length SL1 is 24.9 mm. However, the axial spline tooth length SL1 is not limited to this embodiment and the above range. As seen in FIG. 15, the total number of at least ten external spline teeth 40 is equal to or greater than 20. The total number of at least ten external spline teeth 40 is preferably equal to or greater than 25. The total number of at least ten external spline teeth 40 is preferably equal to or greater than 28. The total number of external spline teeth 40 is preferably equal to or less than 72. In this embodiment, the total number of external spline teeth 40 is 29. 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 at least ten external spline teeth are circumferentially arranged relative to the rotation center axis A1 at the first external pitch angle PA11. In other words, at least two of the plurality of external spline teeth 40 are circumferentially arranged relative to the rotation center axis A1 of the bicycle hub assembly 12 at the first external pitch angle PA11. At least two of the at least ten external spline teeth are circumferentially arranged relative to the rotation center axis A1 of the bicycle hub assembly 12 at the second external pitch angle PA12. In other words, at least two of the plurality of external spline teeth 40 are circumferentially arranged relative to the rotation center axis A1 of the bicycle hub assembly 12 at the second external pitch angle PA12. 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 arranged at a first external pitch angle PA11 in the circumferential direction D1. Two of the external spline teeth among the external spline teeth 40 are arranged at a second external pitch angle PA12 in the circumferential direction D1. However, at least two of the external spline teeth among the external spline teeth 40 can be arranged at another external pitch angle in the circumferential direction D1. The first external pitch angle PA11 is in the range of 5 degrees to 36 degrees. The first external pitch angle PA11 is preferably in the range of 10 degrees to 20 degrees. The first external pitch angle PA11 is preferably equal to or less than 15 degrees. In this embodiment, the first external pitch angle PA11 is 12 degrees. However, the first external pitch angle PA11 is not limited to this embodiment and the above range. The second external pitch angle PA12 is in the range of 5 degrees to 36 degrees. In this embodiment, the second external pitch angle PA12 is 24 degrees. However, the second external pitch angle PA12 is not limited to this embodiment and the above range. At least one of the external spline teeth 40 can have a first spline shape different from the second spline shape of another one of the external spline teeth 40. At least one of at least ten external spline teeth 40 can have a first spline size different from the second spline size of another one of at least ten external spline teeth 40. When viewed along the rotation center axis A1, at least one of the external spline teeth 40 has a profile different from the profile of another one of the external spline teeth 40. In this embodiment, the external spline tooth 40X has a first spline shape different from the second spline shape of another one of the external spline teeth 40. The external spline tooth 40X has a first spline size different from the second spline size of another one of the external spline teeth 40. However, as seen in FIG. 16, at least ten external spline teeth 40 can have the same spline shape with each other. At least ten external spline teeth 40 can have the same spline size with each other. At least ten external spline teeth 40 can have the same profile with each other. As can be seen in FIG. 17, each of at least ten external spline teeth 40 has an external spline driving surface 48 and an external spline non-driving surface 50. The plurality of external spline teeth 40 includes a plurality of external spline driving surfaces 48 for receiving a driving rotational force F1 from the bicycle rear sprocket assembly 14 (FIG. 6) during pedaling. The plurality of external spline teeth 40 includes a plurality of external spline non-driving surfaces 50. The external spline driving surface 48 can contact the bicycle rear sprocket assembly 14 to receive the driving rotational force F1 from the bicycle rear sprocket assembly 14 (FIG. 6) during pedaling. The external spline driving surface 48 faces the reverse rotation direction D12. In a state where the bicycle rear sprocket assembly 14 is mounted to the bicycle hub assembly 12, the external spline driving surface 48 faces the internal spline driving surface of the bicycle rear sprocket assembly 14. The external spline non-driving surface 50 is disposed on the reverse side of the external spline driving surface 48 in the circumferential direction D1. The external spline non-driving surface 50 faces the driving rotational direction D11, so as not to receive the driving rotational force F1 from the bicycle rear sprocket assembly 14 during pedaling. In a state where the bicycle rear sprocket assembly 14 is mounted to the bicycle hub assembly 12, the external spline non-driving surface 50 faces the internal spline non-driving surface of the bicycle rear sprocket assembly 14. Each of the at least ten external spline teeth 40 has a circumferential maximum width MW1. The external spline teeth 40 each have a circumferential maximum width MW1. The circumferential maximum width MW1 is defined as the maximum width for receiving a thrust F2 applied to the external spline teeth 40. The circumferential maximum width MW1 is defined based on the linear distance of the external spline driving surface 48. Each of the plurality of external spline driving surfaces 48 includes a radially outermost edge 48A and a radially innermost edge 48B. The external spline driving surface 48 extends from the radially outermost edge 48A to the radially innermost edge 48B. A first reference circle RC11 is defined on the radially innermost edge 48B and centered on the rotation center axis A1. The first reference circle RC11 intersects the external spline non-driving surface 50 at a reference point 50R. The circumferential maximum width MW1 linearly extends from the radially innermost edge 48B to the reference point 50R in the circumferential direction D1. Each of the plurality of external spline non-driving surfaces 50 includes a radially outermost edge 50A and a radially innermost edge 50B. The external spline non-driving surface 50 extends from the radially outermost edge 50A to the radially innermost edge 50B. In this embodiment, the reference point 50R coincides with the radially innermost edge 50B. However, the reference point 50R can be offset from the radially 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 preferably equal to or greater than 60 mm. The sum of the circumferential maximum widths MW1 is preferably equal to or less than 70 mm. In this embodiment, the sum of the circumferential maximum widths MW1 is 60.1 mm. However, the sum of the circumferential maximum widths MW1 is not limited to this embodiment and the above range. As can be seen in FIG. 18, at least one external spline tooth 40 has an external spline major diameter DM11 that is equal to or less than 34 mm. The external spline major diameter DM11 is equal to or less than 33 mm. The external spline major diameter DM11 is equal to or greater than 29 mm. In this embodiment, the external spline major diameter DM11 is 32.6 mm. However, the external spline major diameter DM11 is not limited to this embodiment and the above range. At least one external spline tooth 40 has an external spline minor diameter DM12. At least one external spline tooth 40 has an external spline root circle RC12, and the external spline root circle RC12 has an external spline minor diameter DM12. However, the external spline root circle RC12 may have a different diameter from the external spline minor diameter DM12. The external spline minor diameter DM12 is equal to or less than 32 mm. The external spline minor diameter DM12 is equal to or less than 31 mm. The external spline minor diameter DM12 is equal to or greater than 28 mm. In this embodiment, the external spline minor diameter DM12 is 30.2 mm. However, the external spline minor diameter DM12 is not limited to this embodiment and the above range. The larger diameter portion 42 has an outer diameter DM13 that is greater than the external spline major 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 can be seen in FIG. 17, the plurality of external spline drive surfaces 48 each include a radial length RL11 defined from the radially outermost edge 48A to the radially 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 total of the radial lengths RL11 is equal to or greater than 15 mm. The sum of the radial lengths is equal to or less than 36 mm. In this embodiment, the sum of the radial lengths RL11 is 16.6 mm. However, the sum of the radial lengths RL11 is not limited to this embodiment. The plurality of external spline teeth 40 have an additional radial length RL12. The additional radial length RL12 is respectively defined from the external spline root circle RC12 to the radially outermost ends 40A of the plurality of external spline teeth 40. The sum of the additional radial lengths RL12 is equal to or greater than 20 mm. In this embodiment, the sum of the additional radial lengths RL12 is 31.2 mm. However, the sum of the additional radial lengths RL12 is not limited to this embodiment. At least one of the at least ten external spline teeth 40 is circumferentially symmetric relative to the reference line CL1. In the radial direction relative to the rotational center axis A1, the reference line CL1 extends from the rotational center axis A1 to the circumferential center point CP1 of the radially outermost end 40A of the at least one of the at least ten external spline teeth 40. However, at least one of the external spline teeth 40 may have an asymmetric shape relative to the reference line CL1. At least one of the at least nine external spline teeth 40 includes an external spline drive surface 48 and an external spline non-drive surface 50. At least one of the plurality of external spline drive surfaces 48 has a first external spline surface angle AG11. The first external spline surface angle AG11 is defined between the external spline drive surface 48 and a first radial line L11. The first radial line L11 extends from the rotational center axis A1 of the bicycle hub assembly 12 to the radially outermost edge 48A of the external spline drive surface 48. A first external pitch angle PA11 or a second external pitch angle PA12 is defined between the first radial lines L11 (see, for example, FIG. 15). At least one of the external spline non-drive surfaces 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 a second radial line L12. The second radial line L12 extends from the rotational center axis A1 of the bicycle hub assembly 12 to the radially outermost edge 50A of the external spline non-drive surface 50. In this embodiment, the second external spline surface angle AG12 is equal to the first external spline surface angle AG11. However, the first external spline surface angle AG11 may be different from the second external spline surface angle AG12. The first external spline surface angle AG11 is equal to or less than 6 degrees. The first external spline surface angle AG11 is equal to or greater than 0 degrees. The second external spline surface angle AG12 is equal to or less than 6 degrees. The second external spline surface angle AG12 is equal to or greater than 0 degrees. In this embodiment, the first external spline surface angle AG11 is 5 degrees. The second external spline surface angle AG12 is 5 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. 19 and 20, 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. 1). In this embodiment, the brake rotor support body 34 includes an additional base support 54 and a plurality of additional external spline teeth 52. The additional base support 54 has a tubular shape and extends from the hub body 36 along the rotational center axis A1. The additional external spline teeth 52 extend radially outward from the additional base support 54. The total number of the additional external spline teeth 52 is 52. However, the total number of the additional external spline teeth 52 is not limited to this embodiment. As can be seen in FIG. 20, at least one additional external spline tooth 52 has an additional external spline top diameter DM14. As can be seen in FIG. 21, the additional external spline top diameter DM14 is greater 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 can be equal to or less than the external spline top diameter DM11. The additional external spline top diameter DM14 can be different from the outer diameter DM13 of the larger diameter portion 42. As can be seen in FIG. 21, the hub body 36 includes a first spoke mounting portion 36A and a second spoke mounting portion 36B. A plurality of first spokes SK1 are coupled to the first spoke mounting portion 36A. A plurality of second spokes SK2 are coupled to the second spoke mounting portion 36B. In this embodiment, the first spoke mounting portion 36A includes a plurality of first attachment holes 36A1. The first spokes SK1 extend through the first attachment holes 36A1. The second spoke mounting portion 36B includes a plurality of second attachment holes 36B1. The second spokes SK2 extend through the second attachment holes 36B1. As used herein, the term "spoke mounting portion" encompasses configurations in which the spoke mounting opening has a flange-like shape such that the spoke mounting portion extends radially outward relative to the rotational central axis of the bicycle hub assembly as seen in FIG. 21, and configurations in which the spoke mounting portion is an opening directly formed on the radially outer peripheral surface of the hub body. The second spoke mounting portion 36B is spaced from the first spoke mounting portion 36A in the axial direction D2. The first spoke mounting portion 36A is disposed between the sprocket support body 28 and the second spoke mounting portion 36B in the axial direction D2. The second spoke mounting portion 36B is disposed between the first spoke mounting portion 36A and the brake rotor support body 34 in the axial direction D2. The first spoke mounting portion 36A has a first axially outermost portion 36C. The second spoke mounting portion 36B has a second axially outermost portion 36D. The first axially outermost portion 36C includes a surface facing the first frame BF1 in the axial direction D2 in a state where the bicycle hub assembly 12 is mounted to the bicycle frame BF. The second axially outermost portion 36D includes a surface facing the second frame BF2 in the axial direction D2 in a state where the bicycle hub assembly 12 is mounted to the bicycle frame BF. The hub body 36 includes a first axial length AL1. The first axial length AL1 is defined in the axial direction D2 between a first axially outermost portion 36C of the first spoke mounting portion 36A and a second axially outermost portion 36D of the second spoke mounting portion 36B with respect to the rotational center axis A1 of the bicycle rear sprocket assembly 14. The first axial length AL1 can be equal to or greater than 55 millimeters. The first axial length AL1 can be equal to or greater than 60 millimeters. The first axial length AL1 can be equal to or greater than 65 millimeters. In this embodiment, the first axial length AL1 can be 67 millimeters. However, the first axial length AL1 is not limited to this embodiment and the above range. Examples of the first axial length AL1 include 55.7 millimeters, 62.3 millimeters, and 67 millimeters. As can be seen in FIG. 21, the hub shaft 30 includes a first axially frame abutting surface 30B1 and a second axially frame abutting surface 30C1. The first axially frame abutting surface 30B1 is configured to abut a first portion BF12 of the bicycle frame BF in the axial direction D2 with respect to the rotational center axis A1 of the bicycle rear sprocket assembly 14 in a state where the bicycle hub assembly 12 is mounted to the bicycle frame BF. The second axially frame abutting surface 30C1 is configured to abut a second portion BF22 of the bicycle frame BF in the axial direction D2 in a state where the bicycle hub assembly 12 is mounted to the bicycle frame BF. The first axially frame abutting surface 30B1 is positioned closer to the sprocket support body 28 in the axial direction D2 than the second axially frame abutting surface 30C1. The sprocket support body 28 is disposed between the first axially frame abutting surface 30B1 and the second axially frame abutting surface 30C1 in the axial direction D2. The hub shaft 30 includes a second axial length AL2 defined in the axial direction D2 between the first axially frame abutting surface 30B1 and the second axially frame abutting surface 30C1. The second axial length AL2 can be equal to or greater than 140 millimeters. The second axial length AL2 can be equal to or greater than 145 millimeters. The second axial length AL2 can be equal to or greater than 147 millimeters. The second axial length AL2 can be 148 millimeters. However, the second axial length AL2 is not limited to this embodiment and the above range. Examples of the second axial length AL2 include 142 millimeters, 148 millimeters, and 157 millimeters. The ratio of the first axial length AL1 to the second axial length AL2 may be equal to or greater than 0.3. The ratio of the first axial length AL1 to the second axial length AL2 may be equal to or greater than 0.4. The ratio of the first axial length AL1 to the second axial length AL2 is equal to or less than 0.5. For example, the ratio of the first axial length AL1 (67 millimeters) to the second axial length AL2 (148 millimeters) is approximately 0.45. However, the ratio of the first axial length AL1 to the second axial length AL2 is not limited to this embodiment and the above range. Examples of the ratio of the first axial length AL1 to the second axial length AL2 include approximately 0.42 (AL1 is 62.3 millimeters and AL2 is 148 millimeters), or include approximately 0.39 (AL1 is 55.7 millimeters and AL2 is 142 millimeters). As can be seen in FIG. 6, the sprocket support body 28 includes a first axial end 28B, a second axial end 28C, and an axial sprocket abutting surface 28D. The second axial end 28C is opposite to the first axial end 28B in the axial direction D2. The axial center plane CPL bisects the second axial length AL2 in the axial direction D2. The axial sprocket abutting surface 28D is positioned closer to the axial center plane CPL of the bicycle hub assembly 12 than the first axial end 28B in the axial direction D2. The second axial end 28C is positioned closer to the axial center plane CPL of the bicycle hub assembly 12 than the axial sprocket abutting surface 28D in the axial direction D2. In this embodiment, the axial sprocket abutting surface 28D is provided on the larger diameter portion 42, however, the axial sprocket abutting surface 28D can be provided on other portions of the bicycle hub assembly 12 as needed. In a state where the rear sprocket assembly 14 of the bicycle is mounted on the sprocket support body 28, the axial sprocket abutting surface 28D contacts the rear sprocket assembly 14 of the bicycle. The axial sprocket abutting surface 28D faces the first axial end 28B in the axial direction D2. As can be seen in FIG. 6, the sprocket configuration axial length AL3 is defined in the axial direction D2 between the first axial frame abutting surface 30B1 and the axial sprocket abutting surface 28D of the sprocket support body 28. In this embodiment, the sprocket configuration axial length AL3 is in the range of 35 millimeters to 45 millimeters. For example, the sprocket configuration axial length AL3 is 39.64 millimeters. For example, by omitting the larger diameter portion 42, the sprocket configuration axial length AL3 can also extend up to 44.25 millimeters. However, the sprocket configuration axial length AL3 is not limited to this embodiment and the above range. The larger diameter portion 42 has an axial end 42A that is the farthest from the first axial frame abutting surface 30B1 in the axial direction D2. An additional axial length AL4 is defined in the axial direction D2 from the first axial frame abutting surface 30B1 to the axial end 42A. The additional axial length AL4 is in the range of 38 mm to 47 mm. The additional axial length AL4 can be in the range of 44 mm to 45 mm. The additional axial length AL4 can also be in the range of 40 mm to 41 mm. In this embodiment, the additional axial length AL4 is 44.25 mm. However, the additional axial length AL4 is not limited to this embodiment and the above ranges. The larger diameter axial length AL5 of the larger diameter portion 42 is in the range of 3 mm to 6 mm. In this embodiment, the larger diameter axial length AL5 is 4.61 mm. However, the larger diameter axial length AL5 is not limited to this embodiment and the above ranges. The ratio of the first axial length AL1 to the sprocket arrangement axial length AL3 is in the range of 1.2 to 1.7. For example, if the first axial length AL1 is 55.7 mm and the sprocket arrangement axial length AL3 is 39.64 mm, then the ratio of the first axial length AL1 to the sprocket arrangement axial length AL3 is 1.4. However, the ratio of the first axial length AL1 to the sprocket arrangement axial length AL3 is not limited to this embodiment and the above ranges. For example, if the first axial length AL1 is 62.3 mm and the sprocket arrangement axial length AL3 is 39.64 mm, then the ratio of the first axial length AL1 to the sprocket arrangement axial length AL3 can be 1.57, or if the first axial length AL1 is 67 mm and the sprocket arrangement axial length AL3 is 39.64 mm, then the ratio of the first axial length AL1 to the sprocket arrangement axial length AL3 can be 1.69. As seen in FIG. 22, at least one sprocket includes a plurality of internal spline teeth configured to engage with the bicycle hub assembly 12. At least one sprocket includes at least ten internal spline teeth configured to engage with the bicycle hub assembly 12. In this embodiment, the first sprocket SP1 includes a plurality of internal spline teeth 63 that radially extend inward from the first sprocket body SP1A. The plurality of internal spline teeth 63 are configured to engage with the sprocket support body 28 (FIG. 4) of the bicycle hub assembly 12. As seen in FIG. 23, the total number of at least ten internal spline teeth 63 is equal to or greater than 20. The total number of at least ten internal spline teeth 63 is equal to or greater than 25. The total number of at least ten internal spline teeth 63 of the second sprocket SP2 is equal to or greater than 28. The total number of internal spline teeth 63 is equal to or less than 72. In this embodiment, the total number of internal spline teeth 63 is 29. However, the total number of internal spline teeth 63 is not limited to this embodiment and the above ranges. The plurality of internal spline teeth 63 have an internal spline major diameter DM22. At least ten internal spline teeth 63 have the internal spline major diameter DM22. As can be seen in FIG. 6, the maximum outer diameter MD1 of the inner cavity 38 is greater than the internal spline major diameter DM22. As can be seen in FIG. 6, the tenth sprocket SP10 includes a plurality of internal spline teeth 64 extending radially inward from the tenth sprocket body SP10A. The plurality of internal spline teeth 64 of the tenth sprocket SP10 have a structure substantially the same as the structure of the plurality of internal spline teeth 63 of the first sprocket SP1. Therefore, for the sake of brevity, it will not be described in detail here. The sprockets SP2 to SP9, SP11, and SP12 do not include a plurality of internal spline teeth. However, at least one of these sprockets may include a plurality of internal spline teeth. In this embodiment, the plurality of internal spline teeth 63 may be omitted from the first sprocket SP1. The plurality of internal spline teeth 64 may be omitted from the tenth sprocket SP10. As can be seen in FIG. 24, at least ten internal spline teeth 63 have a first internal pitch angle PA21 and a second internal pitch angle PA22. At least two of the at least ten internal spline teeth 63 of the first sprocket SP1 are circumferentially arranged relative to the rotation center axis A1 of the bicycle rear sprocket assembly 14 at the first internal pitch angle PA21. At least two of the at least ten spline teeth 63 are adjacent to each other in the circumferential direction D1, and there is no other spline tooth therebetween. In other words, at least two of the plurality of internal spline teeth 63 are circumferentially arranged relative to the rotation center axis A1 of the bicycle rear sprocket assembly 14 at the first internal pitch angle PA21. At least two of the plurality of internal spline teeth 63 are circumferentially arranged relative to the rotation center axis A1 at the second internal pitch angle PA22. At least two other of the at least ten internal spline teeth 63 of the first sprocket SP1 are adjacent to each other in the circumferential direction D1, and there is no other spline tooth therebetween. In other words, at least two of the plurality of internal spline teeth 63 of the first sprocket SP1 are circumferentially arranged relative to the rotation center axis A1 at the second internal pitch angle PA22. 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 63 are circumferentially arranged at the first internal pitch angle PA21 in the circumferential direction D1. Two of the internal spline teeth 63 are arranged at the second internal pitch angle PA22 in the circumferential direction D1. However, at least two of the internal spline teeth 63 may be arranged at another internal pitch angle in the circumferential direction D1. The first internal circumferential pitch angle PA21 is in the range of 10 degrees to 20 degrees. The first internal circumferential pitch angle PA21 is in the range of 12 degrees to 15 degrees. The first internal circumferential pitch angle PA21 is in the range of 13 degrees to 14 degrees. In this embodiment, for example, the first internal circumferential pitch angle PA21 is 12 degrees. However, the first internal circumferential pitch angle PA21 is not limited to this embodiment and the above ranges. The second internal circumferential pitch angle PA22 is in the range of 5 degrees to 36 degrees. In this embodiment, the second internal circumferential pitch angle PA22 is 24 degrees. However, the second internal circumferential pitch angle PA22 is not limited to this embodiment and the above ranges. At least one of at least ten internal spline teeth 63 has a first spline shape different from a second spline shape of another one of at least ten internal spline teeth 63. At least one of at least ten internal spline teeth 63 has a first spline size different from a second spline size of another one of at least ten internal spline teeth 63. At least one of at least ten internal spline teeth 63 has a cross-sectional shape different from a cross-sectional shape of another one of at least ten internal spline teeth 63. However, as seen in FIG. 25, the internal spline teeth 63 may have the same shape as each other. At least ten internal spline teeth 63 may have the same size as each other. At least ten internal spline teeth 63 may have the same cross-sectional shape as each other. As seen in FIG. 26, at least one of at least ten internal spline teeth 63 includes an internal spline driving surface 66. At least one of at least ten internal spline teeth 63 includes an internal spline non-driving surface 68. At least ten internal spline teeth 63 include a plurality of internal spline driving surfaces 66 for transmitting a driving rotational force F1 to a bicycle hub assembly 12 (FIG. 6) during pedaling. At least ten internal spline teeth 63 include a plurality of internal spline non-driving surfaces 68. The internal spline driving surface 66 may contact a sprocket support body 28 to transmit the driving rotational force F1 from a first sprocket SP1 to the sprocket support body 28 during pedaling. The internal spline driving surface 66 faces a driving rotational direction D11. In a state where a rear sprocket assembly 14 of a bicycle is mounted to the bicycle hub assembly 12, the internal spline driving surface 66 faces an external spline driving surface 48 of the bicycle hub assembly 12. The internal spline non-driving surface 68 is disposed on a reverse side of the internal spline driving surface 66 in a circumferential direction D1. The internal spline non-driving surface 68 faces a reverse rotational direction D12, so as not to transmit the driving rotational force F1 from the first sprocket SP1 to the sprocket support body 28 during pedaling. In a state where the rear sprocket assembly 14 of the bicycle is mounted to the bicycle hub assembly 12, the internal spline non-driving surface 68 faces an external spline non-driving surface 50 of the bicycle hub assembly 12. At least ten internal spline teeth 63 each have a circumferential maximum width MW2. The internal spline teeth 63 each have a circumferential maximum width MW2. The circumferential maximum width MW2 is defined as the maximum width for receiving the thrust force F3 applied to the internal spline teeth 63. The circumferential maximum width MW2 is defined based on the linear distance of the internal spline driving surface 66. A plurality of internal spline driving surfaces 66 each include a radially outermost edge 66A and a radially innermost edge 66B. A second reference circle RC21 is defined on the radially outermost edge 66A and centered on the rotation center axis A1. The second reference circle RC21 intersects the internal spline non-driving surface 68 at a reference point 68R. The circumferential maximum width MW2 linearly extends from the radially innermost edge 66B to the reference point 68R in the circumferential direction D1. The internal spline non-driving surface 68 includes a radially outermost edge 68A and a radially innermost edge 68B. The internal spline non-driving surface 68 extends from the radially outermost edge 68A to the radially innermost edge 68B. The reference point 68R is provided between the radially outermost edge 68A and the radially innermost edge 68B. The sum of the circumferential maximum widths MW2 is equal to or greater than 40 millimeters. The sum of the circumferential maximum widths MW2 can be equal to or greater than 45 millimeters. The sum of the circumferential maximum widths MW2 can be equal to or greater than 50 millimeters. In this embodiment, the sum of the circumferential maximum widths MW2 is 50.8 millimeters. However, the sum of the circumferential maximum widths MW2 is not limited to this embodiment. As seen in FIG. 23, at least ten internal spline teeth 63 have an internal spline root diameter DM21. A plurality of internal spline teeth 63 have an internal spline root diameter DM21. The maximum outer diameter MD1 of the inner cavity 38 is greater than the internal spline root diameter DM21. At least one internal spline tooth 63 of the first sprocket SP1 has an internal spline tooth root circle RC22 having an internal spline root diameter DM21. The internal spline root diameter DM21 is equal to or less than 34 millimeters. The internal spline root diameter DM21 of the first sprocket SP1 is equal to or less than 33 millimeters. The internal spline root diameter DM21 of the first sprocket SP1 is equal to or greater than 29 millimeters. In this embodiment, the internal spline root diameter DM21 of the first sprocket SP1 is 32.8 millimeters. However, the internal spline root diameter DM21 of the first sprocket SP1 is not limited to this embodiment and the above range. The internal spline top diameter DM22 of the first sprocket SP1 is equal to or less than 32 millimeters. The internal spline top diameter DM22 is equal to or less than 31 millimeters. The internal spline top diameter DM22 is equal to or greater than 28 millimeters. In this embodiment, the internal spline top diameter DM22 is 30.4 millimeters. However, the internal spline top diameter DM22 is not limited to this embodiment and the above range. As shown in FIG. 22, the first sprocket SP1 has a maximum tip diameter TD1. The maximum tip diameter TD1 is the maximum outer diameter defined by a plurality of first sprocket teeth SP1B. The ratio of the internal spline root diameter DM21 (FIG. 23) to the maximum tip diameter TD1 is in the range of 0.15 to 0.18. In this embodiment, the ratio of the internal spline root diameter DM21 to the maximum tip diameter TD1 is 0.15. However, the ratio of the internal spline root diameter DM21 to the maximum tip diameter TD1 is not limited to this embodiment and the above range. As shown in FIG. 26, the plurality of internal spline drive surfaces 66 include a radially outermost edge 66A and a radially innermost edge 66B. Each of the plurality of internal spline drive surfaces 66 includes a radial length RL21 defined from the radially outermost edge 66A to the radially innermost edge 66B. The sum of the radial lengths RL21 of the plurality of internal spline drive 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. The sum of the radial lengths RL21 is equal to or less than 36 mm. In this embodiment, the sum of the radial lengths RL21 is 16.6 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 63 have an additional radial length RL22. The additional radial length RL22 is defined respectively from the internal spline root circle RC22 to the radially innermost end 63A of the plurality of internal spline teeth 63. 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 34.8 mm. However, the sum of the additional radial lengths RL22 is not limited to this embodiment and the above range. At least one of at least ten internal spline teeth 63 of the first sprocket SP1 is circumferentially symmetric with respect to a reference line CL2. In the radial direction with respect to the rotation center axis A1, the reference line CL2 extends from the rotation center axis A1 to the circumferential center point CP2 of the radially innermost end 63A of the at least one of the at least ten internal spline teeth 63. However, at least one of the internal spline teeth 63 may have an asymmetric shape with respect to the reference line CL2. At least one of the internal spline teeth 63 includes an internal spline drive surface 66 and an internal spline non-drive surface 68. The internal spline drive surface has a first internal spline surface angle AG21. The first internal spline surface angle AG21 is defined between the internal spline drive surface 66 and a first radial line L21. The first radial line L21 extends from the rotation center axis A1 of the rear sprocket assembly 14 of the bicycle to the radially outermost edge 66A of the internal spline drive surface 66. A first internal pitch angle PA21 or a second internal pitch angle PA22 is defined between the first radial lines L21 (see, for example, FIG. 24). The non - driving surface 68 of the internal spline has a second internal spline surface angle AG22. The second internal spline surface angle AG22 is defined between the non - driving surface 68 of the internal spline and the second radial line L22. The second radial line L22 extends from the rotation central axis A1 of the rear sprocket assembly 14 of the bicycle to the radially outermost edge 68A of the non - driving surface 68 of the internal spline. In this embodiment, the second internal spline surface angle AG22 is equal to the first internal spline surface angle AG21. However, the first internal spline surface angle AG21 may be different from the second internal spline surface angle AG22. The first internal spline surface angle AG21 is in the range of 0 degrees to 6 degrees. The second internal spline surface angle is in the range of 0 degrees to 6 degrees. In this embodiment, the first internal spline surface angle AG21 is 5 degrees. The second internal spline surface angle AG22 is 5 degrees. However, the first internal spline surface angle AG21 and the second internal spline surface angle AG22 are not limited to this embodiment and the above range. As can be seen in FIG. 27, the internal spline teeth 63 cooperate with the external spline teeth 40 to transmit the driving rotational force F1 from the first sprocket SP1 to the sprocket support body 28. The internal spline driving surface 66 may contact the external spline driving surface 48 to transmit the driving rotational force F1 from the first sprocket SP1 to the sprocket support body 28. In a state where the internal spline driving surface 66 contacts the external spline driving surface 48, the non - driving surface 68 of the internal spline is spaced apart from the non - driving surface 50 of the external spline. As can be seen in FIGS. 15 and 16, the sprocket support body 28 includes a hub indicator 28I provided at the axial end of the base support member 41. When viewed along the rotation central axis A1, the hub indicator 28I is provided in the region of the second external pitch angle PA12. In this embodiment, the hub indicator 28I includes a small dot. However, the hub indicator 28I may include other shapes such as a triangle and a straight line. Additionally, the hub indicator 28I may be a separate member attached to the sprocket support body 28 by a joining structure (such as an adhesive). The position of the hub indicator 28I is not limited to this embodiment. As can be seen in FIG. 7, the twelfth sprocket SP12 includes a sprocket indicator SP12I provided at the axial end of the twelfth sprocket body SP12A. In this embodiment, the sprocket indicator SP12I includes a small dot. However, the sprocket indicator SP12I may include other shapes such as a triangle and a straight line. Additionally, the sprocket indicator SP12I may be a separate member attached to the sprocket SP12 by a joining structure (such as an adhesive). The position of the sprocket indicator SP12I is not limited to this embodiment. The sprocket indicator SP12I may be provided to any one of the other sprockets SP1 to SP11. As seen in FIG. 6, the bicycle hub assembly 12 further includes a freewheel structure 78. The sprocket support body 28 is operatively coupled to the hub body 36 by the freewheel structure 78. The freewheel structure 78 is configured to couple the sprocket support body 28 to the hub body 36 to rotate the sprocket support body 28 together with the hub body 36 in the driving rotation direction D11 (FIG. 5) during pedaling. The freewheel structure 78 is configured to allow the sprocket support body 28 to rotate relative to the hub body 36 in the reverse rotation direction D12 (FIG. 5) during the inertial coasting period. Thus, the freewheel structure 78 can be interpreted as a one-way coupling structure. The freewheel structure 78 will be described in detail later. The bicycle hub assembly 12 includes a first bearing 79A and a second bearing 79B. The first bearing 79A and the second bearing 79B are disposed between the sprocket support body 28 and the hub shaft 30 to rotatably support the sprocket support body 28 relative to the hub shaft 30 about 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 metallic 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. Second Embodiment The bicycle rear sprocket assembly 214 according to the second embodiment will be described below with reference to FIGS. 28 to 30. The bicycle rear sprocket assembly 214 has the same structure as the structure of the bicycle rear sprocket assembly 14 except for the first sprocket SP1 and the second sprocket SP2. Therefore, the elements having substantially the same functions as those elements in the first embodiment will be numbered the same here, and will not be described and / or illustrated in detail again here for the sake of brevity. As seen in FIG. 28, in the bicycle rear sprocket assembly 214, the plurality of first sprocket teeth SP1B includes at least one first tooth SP1W and at least one second tooth SP1N. In this embodiment, the plurality of first sprocket teeth SP1B includes a plurality of first teeth SP1W and a plurality of second teeth SP1N. The first teeth SP1W and the second teeth SP1N are alternately arranged in the circumferential direction D1. The total number of the first teeth SP1W is equal to the total number of the second teeth SP2N. That is, in this embodiment, the total number of the first sprocket teeth SP1B is even. However, the total number of the first teeth SP1W is not limited to this embodiment. The total number of the second teeth SP1N is not limited to this embodiment. At least one of the first teeth SP1W may be omitted from the first sprocket SP1. At least one of the second teeth SP1N may be omitted from the first sprocket SP1. As can be seen in FIG. 29, at least one first tooth SP1W has a first maximum axial width W1 defined in the axial direction D2 with respect to the rotational center axis A1. In this embodiment, each of the first teeth SP1W has the first maximum axial width W1. The first maximum axial width W1 is smaller than the axial length of the outer chain space 20A1 defined between a pair of opposing outer link plates 20A. As can be seen in FIG. 30, at least one second tooth SP1N has a second maximum axial width W2 defined in the axial direction D2. In this embodiment, each of the second teeth SP1N has the second maximum axial width W2. The first maximum axial width W1 is greater than the second maximum axial width W2. The first maximum axial width W1 is greater than the axial length of the inner chain space 20B1 defined between a pair of opposing inner link plates 20B. The second maximum axial width W2 is smaller than the axial length of the inner chain space 20B1. The first teeth SP1W are configured to engage with a pair of opposing outer link plates 20A. The second teeth SP1N are configured to engage with a pair of opposing inner link plates 20B. As can be seen in FIG. 28, the plurality of second sprocket teeth SP2B includes at least one first tooth SP2W and at least one second tooth SP2N. In this embodiment, the plurality of second sprocket teeth SP2B includes a plurality of first teeth SP2W and a plurality of second teeth SP2N. The first tooth SP2W has a structure substantially the same as that of the first tooth SP1W. The second tooth SP2N has a structure substantially the same as that of the second tooth SP1N. Therefore, for the sake of brevity, it will not be described in detail here. Third Embodiment The bicycle rear sprocket assembly 314 according to the third embodiment will be described below with reference to FIGS. 31 to 33. Except for the locking member 32, the bicycle rear sprocket assembly 314 has the same structure as the bicycle rear sprocket assembly 14. Therefore, the elements having substantially the same functions as those in the first embodiment will be numbered the same here, and for the sake of brevity, they will not be described and / or explained in detail again here. As can be seen in FIG. 31, the bicycle rear sprocket assembly 314 includes a locking member 332. The locking member 332 is configured to prevent the sprockets SP1 to SP12 from axially moving relative to the sprocket support body 328 of the bicycle hub assembly 312 in a state where the locking member 332 is attached to the sprocket support body 328. Except for the sprocket support body 328, the bicycle hub assembly 312 has a structure substantially the same as that of the bicycle hub assembly 12. The sprocket support body 328 includes a plurality of external spline teeth 40 and an external thread portion 328B. The axial length of the external spline teeth 40 of the sprocket support body 328 is shorter than the axial length of the external spline teeth 40 of the sprocket support body 28. The plurality of external spline teeth 40 are arranged in the axial direction D2 between the external thread portion 328B and the first spoke mounting portion 36A. As can be seen in FIG. 32, the sprockets SP1 and SP2 have a structure substantially the same as that of the modified sprockets SP1 and SP2 of the first embodiment shown in FIG. 10. Thus, the plurality of first sprocket teeth SP1B and the plurality of second sprocket teeth SP2B are integrally provided with each other as a single-piece integral member. The locking member 332 is rotatably coupled to the sprockets SP1 to SP12 about the rotation center axis A1. The sprockets SP1 to SP12, the coupling members CM1 to CM11, and the locking member 332 define an inner cavity 38. The locking member 332 includes a first axial end 332A and an internal thread portion 332B. The internal thread portion 332B is configured to be screwed with the external thread portion 328B in a threaded manner. The plurality of external spline teeth 40 mesh with the plurality of internal spline teeth 63 of the cover member 14A attached to the first sprocket SP1. In a state where the locking member 332 is fastened to the sprocket support body 28 by the external thread portion 328B and the internal thread portion 332B, the cover member 14A is held axially between the larger diameter portion 42 and the first axial end 332A of the locking member 332. As can be seen in FIG. 33, the locking member 332 has a second axial end 332C and a tool engagement portion 332F. The internal thread portion 332B is provided between the first axial end 332A and the second axial end 332C. The tool engagement portion 332F is provided at the second axial end 332C. In this embodiment, the tool engagement portion 332F includes a plurality of engagement grooves 332G, and the engagement grooves 332G will engage with a fastening tool (not shown in the figure) when the locking member 332 is threadedly attached to the sprocket support body 28 by the external thread portion 328B and the internal thread portion 332B. As used herein, the term "comprising" and its derivatives are intended to be open terms specifying the presence of stated features, elements, components, groups, integers, and / or steps, but not excluding the presence of other unstated features, elements, components, groups, integers, and / or steps. This concept also applies to words of similar meaning, such as the terms "having", "including" and their derivatives. The terms "member", "section", "portion", "component", "element", "body" and "structure" may have a dual meaning of a single component or a plurality of components when used in the singular form. Ordinal numbers such as "first" and "second" described in this application are only 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". As used herein, the term "pair" can cover configurations in which the paired elements have different shapes or structures from each other, in addition to configurations in which the paired elements have the same shape or structure as each other. Accordingly, the terms "a", "one or more", and "at least one" are used interchangeably herein. Finally, degree terms such as "substantially", "about", and "approximately" as used herein mean a reasonable amount of deviation of the modified term such that the end result is not significantly changed. All numerical values described in this application can be understood to include terms such as "substantially", "about", and "approximately". Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. Accordingly, it is to be understood that within the scope of the appended claims, the invention may be practiced in other ways than as specifically described herein. 10: Bicycle drive system 12: Bicycle hub assembly 14: Bicycle rear sprocket assembly 14A: Cover member 16: Bicycle brake rotor 18: Crank assembly 20: Bicycle chain 20A: Outer link plate 20A1: Outer link space 20B: Inner link plate 20B1: Inner link space 22: Crankshaft 24: Right crank arm 26: Left crank arm 27: Front sprocket 28: Sprocket support body 28A: Internal thread portion 28B: First axial end 28C: Second axial end 28D: Axial sprocket adjacent surface 28I: Hub indicator 30: Hub shaft 30A: Axial through hole 30B: First shaft end 30B1: First axial frame adjacent surface 30C: Second shaft end 30C1: Second axial frame adjacent surface 32: Locking member 32A: Tubular body 32B: External thread portion 32C: Radial protrusion 32D: First axial end 32E: Second axial end 32F: Tool engagement portion 32G: Engagement groove 34: Brake rotor support body 35: Rotor locking member 36: Hub body 36A: First spoke mounting portion 36A1: First attachment hole 36B: Second spoke mounting portion 36B1: Second attachment hole 36C: First axially outermost portion 36D: Second axially outermost portion 38: Inner cavity 40: External spline teeth 40A: Radially outermost end 40X: External spline teeth 41: Base support 42: Larger diameter portion 42A: Axial end 44: Flange 46: Helical external spline teeth 48: External spline drive surface 48A: Radially outermost edge 48B: Radially innermost edge 50: External spline non-drive surface 50A: Radially outermost edge 50B: Radially innermost edge 50R: Reference point 52: Additional external spline teeth 54: Additional base support 63: Internal spline teeth 63A: Radially innermost end 64: Internal spline teeth 66: Internal spline drive surface 66A: Radially outermost edge 66B: Radially innermost edge 68: Internal spline non-drive surface 68A: Radially outermost edge 68B: Radially innermost edge 68R: Reference point 78: Freewheel structure 79A: First bearing 79B: Second bearing 132F2: Protrusion 132F3: Engagement groove 214: Bicycle rear sprocket assembly 312: Bicycle hub assembly 314: Bicycle rear sprocket assembly 328: Sprocket support body 328B: External thread portion 332: Locking member 332A: First axial end 332B: Internal thread portion 332C: Second axial end 332F: Tool engagement portion 332G: Engagement groove A1: Rotation center axis AG11: First external spline surface angle AG12: Second external spline surface angle AG21: First internal spline surface angle AG22: Second internal spline surface angle AL1: First axial length AL2: Second axial length AL3: Sprocket configuration axial lengthAL4: Additional Axial Length AL5: Axial Length of Larger Diameter BF: Bicycle Frame BF1: First Frame BF2: Second Frame BF11: First Groove BF12: First Part BF21: Second Groove BF22: Second Part CL1: Reference Line CL2: Reference Line CM1: Coupling Member CM1A: Coupling Pin CM2: Second Coupling Member CM3: Third Coupling Member CM4: Fourth Coupling Member CM5: Fifth Coupling Member CM6: Sixth Coupling Member CM7: Seventh Coupling Member CM8:第八Coupling Member CM9: Ninth Coupling Member CM10: Tenth Coupling Member CP1: Circumferential Center Point CP2: Circumferential Center Point CPL: Axial Center Plane D1: Circumferential Direction D2: Axial Direction D11: Driving Rotation Direction D12: Reverse Rotation Direction DM11: Outer Spline Top Diameter DM12: Outer Spline Bottom Diameter DM13: Outer Diameter DM14: Additional Outer Spline Top Diameter DM21: Inner Spline Bottom Diameter DM22: Inner Spline Top Diameter F1: Driving Rotation Force F2: Thrust Force F3: Thrust Force L11: First Radial Line L12: Second Radial Line L21: First Radial Line L22: Second Radial Line MD1: Maximum Outer Diameter MW1: Maximum Circumferential Width MW2: Maximum Circumferential Width PA11: First External Pitch Angle PA12: Second External Pitch Angle PA21: First Internal Pitch Angle PC1: Pitch Circle PC2: Pitch Circle PC3: Pitch Circle PC4: Pitch Circle PC5: Pitch Circle PC6: Pitch Circle PC7: Pitch Circle PC8: Pitch Circle PC9: Pitch Circle PC10: Pitch Circle PC11: Pitch Circle PC12: Pitch Circle PCD1: Pitch Circle Diameter PCD2: Pitch Circle Diameter PCD3: Pitch Circle Diameter PCD4: Pitch Circle Diameter PCD5: Pitch Circle Diameter PCD6: Pitch Circle Diameter PCD7: Pitch Circle Diameter PCD8: Pitch Circle Diameter PCD9: Pitch Circle Diameter PCD10: Pitch Circle Diameter PCD11: Pitch Circle Diameter PCD12: Pitch Circle Diameter RC11: First Reference Circle RC12: Outer Spline Root Circle RC21: Second Reference Circle RC22: Inner Spline Root Circle RL11: Radial Length RL12: Additional Radial Length RL22: Additional Radial Length SK1: First Spoke SK2: Second Spoke SL1: Axial Spline Tooth Length SP1: Bicycle Sprocket / First Sprocket SP1A: First Sprocket Body SP1B: First Sprocket Tooth SP1W: First Tooth SP1N: Second Tooth SP2: Bicycle Sprocket / Second Sprocket SP2A: Second Sprocket Body SP2B: Second Sprocket Tooth SP2W: First Tooth SP2N: Second Tooth SP3: Bicycle Sprocket / Third Sprocket SP3A: Third Sprocket Body SP3B: Third Sprocket Tooth SP4: Bicycle Sprocket / Fourth Sprocket SP4A: Fourth Sprocket Body SP4B: Fourth Sprocket ToothSP5: Bicycle Sprocket / Fifth Sprocket SP5A: Fifth Sprocket Body SP5B: Fifth Sprocket Tooth SP6: Bicycle Sprocket / Sixth Sprocket SP6A: Sixth Sprocket Body SP6B: Sixth Sprocket Tooth SP7: Bicycle Sprocket / Seventh Sprocket SP7A: Seventh Sprocket Body SP7B: Seventh Sprocket Tooth SP8: Bicycle Sprocket / Eighth Sprocket SP8A: Eighth Sprocket Body SP8B: Eighth Sprocket Tooth SP9: Bicycle Sprocket / Ninth Sprocket SP9A: Ninth Sprocket Body SP9B: Ninth Sprocket Tooth SP10: Bicycle Sprocket / Tenth Sprocket SP10A: Tenth Sprocket Body SP10B: Tenth Sprocket Tooth SP11: Bicycle Sprocket / Eleventh Sprocket SP11A: Eleventh Sprocket Body SP11B: Eleventh Sprocket Tooth SP12: Bicycle Sprocket / Twelfth Sprocket SP12A: Twelfth Sprocket Body SP12B: Twelfth Sprocket Tooth TD1: Maximum Tooth Tip Diameter W1: First Maximum Axial Width W2: Second Maximum Axial Width WS: Wheel Fastening Structure WS1: Fastening Rod When considered in conjunction with the accompanying drawings, reference to the following embodiments will make the more complete evaluation of the present invention and many of its attendant advantages readily available and will also become better understood. FIG. 1 is a schematic view of a bicycle drive system including a rear sprocket assembly of a bicycle according to a first embodiment. FIG. 2 is an exploded perspective view of the bicycle drive system illustrated in FIG. 1. FIG. 3 is a cross-sectional view of the bicycle drive system taken along line III-III of FIG. 2. FIG. 4 is a perspective view of a bicycle hub assembly of the bicycle drive system illustrated in FIG. 2, the bicycle hub assembly having a locking member of the rear sprocket assembly of the bicycle. FIG. 5 is a side view of the rear sprocket assembly of the bicycle drive system illustrated in FIG. 2. FIG. 6 is an enlarged cross-sectional view of the bicycle drive system illustrated in FIG. 4. FIG. 7 is a partial side view of the rear sprocket assembly of the bicycle drive system illustrated in FIG. 2. FIG. 8 is an enlarged cross-sectional view of a modified bicycle drive system. FIG. 9 is an enlarged cross-sectional view of another modified bicycle drive system. FIG. 10 is an enlarged cross-sectional view of another modified bicycle drive system. FIG. 11 is a perspective view of a locking member of a modified rear sprocket assembly of a bicycle. FIG. 12 is a perspective view of a sprocket support body of the bicycle hub assembly illustrated in FIG. 4. FIG. 13 is another perspective view of the sprocket support body of the bicycle hub assembly illustrated in FIG. 4. Figure 14 is a rear view of the sprocket support body of the bicycle hub assembly illustrated in Figure 4. Figure 15 is a side view of the sprocket support body of the bicycle hub assembly illustrated in Figure 4. Figure 16 is a side view of the sprocket support body of the modified bicycle hub assembly. Figure 17 is an enlarged cross-sectional view of the sprocket support body illustrated in Figure 15. Figure 18 is a cross-sectional view of the sprocket support body illustrated in Figure 15. Figure 19 is a perspective view of the bicycle hub assembly illustrated in Figure 4. Figure 20 is a side view of the bicycle hub assembly illustrated in Figure 4. Figure 21 is a rear view of the bicycle hub assembly illustrated in Figure 4. Figure 22 is a side view of the sprocket of the bicycle rear sprocket assembly illustrated in Figure 2. Figure 23 is a partially enlarged side view of the sprocket illustrated in Figure 22. Figure 24 is a partially enlarged side view of the sprocket illustrated in Figure 22. Figure 25 is a partially enlarged side view of the modified sprocket. Figure 26 is an enlarged cross-sectional view of the sprocket illustrated in Figure 22. Figure 27 is another cross-sectional view of the bicycle drive system illustrated in Figure 2. Figure 28 is a side view of the bicycle rear sprocket assembly according to the second embodiment. Figure 29 is a cross-sectional view of the first tooth of the bicycle rear sprocket assembly illustrated in Figure 28. Figure 30 is a cross-sectional view of the second tooth of the bicycle rear sprocket assembly illustrated in Figure 28. Figure 31 is an exploded rear view of the bicycle rear sprocket assembly according to the third embodiment. Figure 32 is a partial cross-sectional view of the bicycle rear sprocket assembly illustrated in Figure 31. Figure 33 is a cross-sectional view of the locking member of the bicycle rear sprocket assembly illustrated in Figure 31. 10: Bicycle drive system 12: Bicycle hub assembly 14: Bicycle rear sprocket assembly 28: Sprocket support body 28A: Internal thread portion 28B: First axial end 28C: Second axial end 28D: Axial sprocket adjacent surface 30: Hub shaft 30B: First shaft end 30B1: First axial frame adjacent surface 32: Locking member 32A: Tubular body 32B: External thread portion 32C: Radial protrusion 32E: Second axial end 36: Hub body 36A: First spoke mounting portion 38: Inner cavity 42: Larger diameter portion 42A: Axial end 44: Flange 64: Internal spline teeth 78: Freewheel structure 79A: First bearing 79B: Second bearing A1: Axis of rotation AL3: Axial length of sprocket arrangement AL4: Additional axial length AL5: Axial length of larger diameter CM1: Coupling member CM1A: Coupling pin CM2: Second coupling member CM3: Third coupling member CM4: Fourth coupling member CM5: Fifth coupling member CM6: Sixth coupling member CM7: Seventh coupling member CM8: Eighth coupling member CM9: Ninth coupling member CM10: Tenth coupling member CPL: Axial center plane D2: Axial direction DM22: Top diameter of internal spline MD1: Maximum outside diameter PCD1: Pitch circle diameter PCD2: Pitch circle diameter PCD3: Pitch circle diameter SP1: Bicycle sprocket / First sprocket SP1A: First sprocket body SP1B: First sprocket teeth SP2: Bicycle sprocket / Second sprocket SP2A: Second sprocket body SP2B: Second sprocket teeth SP3: Bicycle Sprocket / Third Sprocket SP3A: Third Sprocket Body SP3B: Third Sprocket Teeth SP4: Bicycle Sprocket / Fourth Sprocket SP4A: Fourth Sprocket Body SP4B: Fourth Sprocket Teeth SP5: Bicycle Sprocket / Fifth Sprocket SP5A: Fifth Sprocket Body SP5B: Fifth Sprocket Teeth SP6: Bicycle Sprocket / Sixth Sprocket SP6A: Sixth Sprocket Body SP6B: Sixth Sprocket Teeth SP7: Bicycle Sprocket / Seventh Sprocket SP7A: Seventh Sprocket Body SP7B: Seventh Sprocket Teeth SP8: Bicycle Sprocket / Eighth Sprocket SP8A: Eighth Sprocket Body SP8B: Eighth Sprocket Teeth SP9: Bicycle Sprocket / Ninth Sprocket SP9A: Ninth Sprocket Body SP9B: Ninth Sprocket Teeth SP10: Bicycle Sprocket / Tenth Sprocket SP10A: Tenth Sprocket Body SP10B: Tenth Sprocket Teeth SP11: Bicycle Sprocket / Eleventh Sprocket SP11A: Eleventh Sprocket Body SP11B: Eleventh Sprocket Teeth SP12: Bicycle Sprocket / Twelfth Sprocket SP12A: Twelfth Sprocket Body SP12B: Twelfth Sprocket Teeth

Claims

1. A bicycle rear sprocket assembly having a central axis of rotation, the bicycle rear sprocket assembly comprising: A sprocket includes a plurality of internal splines configured to engage with a bicycle hub assembly; the plurality of sprockets are integrally configured as a single-piece component, including a minimum sprocket configured to be axially positioned outward from an axial end of a sprocket support body of the bicycle hub assembly relative to the rotation center axis when the bicycle rear sprocket assembly is mounted to one of the bicycle hub assemblies; wherein each of the plurality of internal splines includes an internal spline drive surface to transmit rotational force to the bicycle hub assembly; each of the plurality of internal spline drive surfaces includes a radial outermost edge, a radial innermost edge, and a radial length defined from the radial outermost edge to the radial innermost edge; and the sum of the radial lengths of the plurality of internal spline drive surfaces is equal to or greater than 7 mm.

2. The bicycle rear sprocket assembly of claim 1 further includes: A locking member configured to fasten to the sprocket support body to hold the bicycle rear sprocket assembly relative to the sprocket support body in the axial direction.

3. The bicycle rear sprocket assembly of claim 2, wherein the locking member comprises: a tubular body including a first axial end and a second axial end; an externally threaded portion provided to the first axial end of the tubular body for screwing into an internally threaded portion of the sprocket support body of the bicycle hub assembly in the state where the bicycle rear sprocket assembly is mounted to the bicycle hub assembly; and a radially projecting portion extending radially outward from the second axial end of the tubular body in a radial direction relative to the rotation center axis and configured to abut the smallest sprocket in the state where the bicycle rear sprocket assembly is mounted to the bicycle hub assembly.

4. The bicycle rear sprocket assembly of claim 3, wherein the smallest sprocket is configured to be positioned in the axial direction between the axial end of the sprocket support body of the bicycle hub assembly and the radial protrusion of the locking member in the axial direction when the bicycle rear sprocket assembly is mounted to the bicycle hub assembly.

5. The bicycle rear sprocket assembly of claim 1, wherein the plurality of internal spline teeth have an internal spline tip diameter; and an inner cavity provided to have a maximum outer diameter greater than the internal spline tip diameter.

6. The bicycle rear sprocket assembly of claim 5, wherein the detachable sprocket has a pitch circle diameter greater than the maximum outer diameter of the inner cavity.

7. The bicycle rear sprocket assembly of claim 5 or 6, wherein the plurality of internal spline teeth have an internal spline base diameter, and the maximum outer diameter of the cavity is greater than the internal spline base diameter.

8. The bicycle rear sprocket assembly of claim 1, wherein the plurality of internal splines have a first internal pitch angle and a second internal pitch angle different from the first internal pitch angle.

9. The bicycle rear sprocket assembly of claim 1, wherein at least one of the plurality of internal spline teeth has a first spline shape, the first spline shape being different from a second spline shape of one of the other of the plurality of internal spline teeth.

10. The bicycle rear sprocket assembly of claim 1, wherein at least one of the plurality of internal splines has a first spline size, the first spline size being different from a second spline size of one of the other of the plurality of internal splines.

11. The bicycle rear sprocket assembly of claim 1, wherein the internal spline drive surface has a first internal spline surface angle, the first internal spline surface angle being defined between the internal spline drive surface and a radial line extending from the rotational center axis of the bicycle rear sprocket assembly to the radial outermost edge of the internal spline drive surface; and the first internal spline surface angle being in the range of 0 degrees to 6 degrees.

12. The bicycle rear sprocket assembly of claim 1, further comprising: A coupling member that couples the detachable sprocket to one of the plurality of sprockets.

13. The bicycle rear sprocket assembly of claim 1, wherein the minimum sprocket comprises a plurality of sprocket teeth, and the total number of one of the plurality of sprocket teeth of the minimum sprocket is equal to or less than 10.

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