Bicycle rear sprocket assembly and bicycle drive train

1. A bicycle rear sprocket assembly configured to be mounted to a sprocket support body of a bicycle rear hub assembly, the bicycle rear sprocket assembly comprising:

a plurality of bicycle sprockets comprising:

a first sprocket including:

a first opening having a first minimum diameter that is smaller than a minimum outer diameter of the sprocket support body of the bicycle rear hub assembly; and

a second sprocket including:

a second opening having a second minimum diameter that is equal to or larger than the minimum outer diameter of the sprocket support body of the bicycle rear hub assembly; and

at least ten internal spline teeth configured to engage with the sprocket support body of the bicycle rear hub assembly, wherein

the second sprocket is adjacent to the first sprocket without another sprocket between the first sprocket and the second sprocket in an axial direction with respect to a rotational center axis of the bicycle rear sprocket assembly.

2. The bicycle rear sprocket assembly according to claim 1 , further comprising

a lock member including:

a tubular body extending through the first opening of the first sprocket in a state where the bicycle rear sprocket assembly is mounted to the bicycle rear hub assembly, the tubular body including:

a first axial end; and

a second axial end opposite to the first axial end in the axial direction with respect to the rotational center axis of the bicycle rear sprocket assembly, the first axial end being positioned closer to an axial center plane of the bicycle rear hub assembly than the second axial end in the state where the bicycle rear sprocket assembly is mounted to the bicycle rear hub assembly;

a male thread portion provided to the first axial end to engage with a female thread portion of the sprocket support body of the bicycle rear hub assembly in the state where the bicycle rear sprocket assembly is mounted to the bicycle rear hub assembly; and

a radial projection extending radially outwardly from the second axial end with respect to the rotational center axis to restrict an axial movement of the first sprocket relative to the sprocket support body of the bicycle rear hub assembly in the state where the bicycle rear sprocket assembly is mounted to the bicycle rear hub assembly.

3. The bicycle rear sprocket assembly according to claim 2 , wherein

the first sprocket includes:

a first inward facing side; and

a first outward facing side opposite to the first inward facing side in the axial direction, and

the radial projection is configured to abut against the first sprocket in the first outward facing side.

4. The bicycle rear sprocket assembly according to claim 3 , wherein

the tubular body has a first external diameter that is equal to or smaller than 27 mm.

5. The bicycle rear sprocket assembly according to claim 4 , wherein

the first external diameter is equal to or larger than 26 mm.

6. The bicycle rear sprocket assembly according to claim 3 , wherein

the radial projection has a second external diameter that is equal to or smaller than 32 mm.

7. The bicycle rear sprocket assembly according to claim 6 , wherein

the second external diameter is equal to or larger than 30 mm.

8. The bicycle rear sprocket assembly according to claim 1 , wherein

the first sprocket includes:

a first inward facing side; and

a first outward facing side opposite to the first inward facing side in the axial direction with respect to the rotational center axis of the bicycle rear sprocket assembly, and

the first sprocket includes a first torque-transmitting structure provided to the first inward facing side to directly or indirectly transmit a pedaling torque to the sprocket support body.

9. The bicycle rear sprocket assembly according to claim 8 , wherein

the first torque-transmitting structure includes at least ten first torque-transmitting teeth.

10. The bicycle rear sprocket assembly according to claim 9 , wherein

a total number of the at least ten first torque-transmitting teeth is equal to or larger than 20.

11. The bicycle rear sprocket assembly according to claim 9 , wherein

a total number of the at least ten first torque-transmitting teeth ranges from 22 to 24.

12. The bicycle rear sprocket assembly according to claim 1 , wherein

a total number of the at least ten internal spline teeth of the second sprocket is equal to or larger than 20.

13. The bicycle rear sprocket assembly according to claim 12 , wherein

the total number of the at least ten internal spline teeth of the second sprocket is equal to or larger than 28.

14. The bicycle rear sprocket assembly according to claim 1 , wherein

the at least ten internal spline teeth of the second sprocket have a first internal pitch angle and a second internal pitch angle different from the first internal pitch angle.

15. The bicycle rear sprocket assembly according to claim 1 , wherein

at least one of the at least ten internal spline teeth of the second sprocket has a first spline shape different from a second spline shape of another of the at least ten internal spline teeth.

16. The bicycle rear sprocket assembly according to claim 1 , wherein

at least one of the at least ten internal spline teeth of the second sprocket has a first spline size different from a second spline size of another of the at least ten internal spline teeth.

17. The bicycle rear sprocket assembly according to claim 1 , wherein

a total tooth number of the first sprocket is equal to or smaller than 10.

18. The bicycle rear sprocket assembly according to claim 1 , wherein

the first sprocket is the smallest sprocket in the bicycle rear sprocket assembly.

19. The bicycle rear sprocket assembly according to claim 1 , further comprising

a sprocket support member including at least ten internal spline teeth configured to engage with the sprocket support body of the bicycle rear hub assembly, wherein

the plurality of bicycle sprockets comprises an additional sprocket configured to be attached to the sprocket support member.

20. The bicycle rear sprocket assembly according to claim 19 , wherein

a total tooth number of the additional sprocket is equal to or larger than 46.

21. The bicycle rear sprocket assembly according to claim 19 , wherein

a total tooth number of the additional sprocket is equal to or larger than 50.

22. The bicycle rear sprocket assembly according to claim 19 , wherein

the additional sprocket is attached to the sprocket support member by adhesive.

23. The bicycle rear sprocket assembly according to claim 19 , wherein

the sprocket support member is made of a non-metallic material including a resin material.

24. The bicycle rear sprocket assembly according to claim 1 , wherein

the plurality of bicycle sprockets comprises a plurality of the second sprockets, and

the plurality of second sprockets each includes the at least ten internal spline teeth configured to engage with the sprocket support body of the bicycle rear hub assembly.

25. The bicycle rear sprocket assembly according to claim 24 , further comprising

a sprocket support member including at least ten internal spline teeth configured to engage with the sprocket support body of the bicycle rear hub assembly, wherein

the plurality of bicycle sprockets comprises an additional sprocket configured to be attached to the sprocket support member.

26. The bicycle rear sprocket assembly according to claim 1 , wherein

a total number of the plurality of bicycle sprockets is equal to or larger than 10.

27. The bicycle rear sprocket assembly according to claim 1 , wherein

a total number of the plurality of bicycle sprockets is equal to or larger than 11.

28. The bicycle rear sprocket assembly according to claim 1 , wherein

a total number of the plurality of bicycle sprockets is equal to or larger than 12.

29. The bicycle rear sprocket assembly according to claim 1 , wherein

the plurality of bicycle sprockets comprises an additional sprocket having a largest tooth-tip diameter,

the at least ten internal spline teeth of the second sprocket have an internal-spline major diameter, and

a ratio of the internal-spline major diameter to the largest tooth-tip diameter ranges from 0.15 to 0.18.

30. The bicycle rear sprocket assembly according to claim 1 , wherein

the plurality of bicycle sprockets comprises an additional sprocket including:

at least one first shifting facilitation area to facilitate a first shifting operation in which a bicycle chain shifts from the additional sprocket to a neighboring smaller sprocket; and

at least one second shifting facilitation area to facilitate a second shifting operation in which the bicycle chain shifts from the neighboring smaller sprocket to the additional sprocket.

31. The bicycle rear sprocket assembly according to claim 1 , wherein

the plurality of bicycle sprockets comprises:

a plurality of the first sprockets, the plurality of first sprockets each including the first opening; and

a plurality of the second sprockets, the plurality of second sprockets each including the second opening and the at least ten internal spline teeth configured to engage with the sprocket support body of the bicycle rear hub assembly.

32. The bicycle rear sprocket assembly according to claim 1 , wherein

at least two internal spline teeth of the at least ten internal spline teeth of the second sprocket are circumferentially arranged at a first internal pitch angle with respect to a rotational center axis of the bicycle rear sprocket assembly, and

the first internal pitch angle ranges from 5 degrees to 36 degrees.

33. The bicycle rear sprocket assembly according to claim 32 , wherein

the first internal pitch angle ranges from 10 degrees to 20 degrees.

34. The bicycle rear hub assembly according to claim 33 , wherein

the first internal pitch angle is equal to or smaller than 15 degrees.

35. The bicycle rear sprocket assembly according to claim 32 , wherein

the first internal pitch angle ranges from 13 degrees to 17 degrees.

36. The bicycle rear sprocket assembly according to claim 1 , wherein

the at least ten internal spline teeth of the second sprocket have an internal-spline major diameter equal to or smaller than 34 mm.

37. The bicycle rear sprocket assembly according to claim 36 , wherein

the internal-spline major diameter of the second sprocket is equal to or smaller than 32 mm.

38. The bicycle rear sprocket assembly according to claim 36 , wherein

the internal-spline major diameter of the second sprocket is equal to or larger than 29 mm.

39. The bicycle rear sprocket assembly according to claim 1 , wherein

the at least ten internal spline teeth of the second sprocket have an internal-spline minor diameter equal to or smaller than 32 mm.

40. The bicycle rear sprocket assembly according to claim 39 , wherein

the internal-spline minor diameter is equal to or smaller than 31 mm.

41. The bicycle rear sprocket assembly according to claim 39 , wherein

the internal-spline minor diameter is equal to or larger than 28 mm.

42. The bicycle rear sprocket assembly according to claim 1 , wherein

the at least ten internal spline teeth includes a plurality of internal-spline driving surfaces to receive a driving rotational force from the bicycle rear hub assembly during pedaling,

the plurality of internal-spline driving surfaces each includes

a radially outermost edge,

a radially innermost edge, and

a radial length defined from the radially outermost edge to the radially innermost edge, and

a total of the radial lengths of the plurality of internal-spline driving surfaces is equal to or larger than 7 mm.

43. The bicycle rear sprocket assembly according to claim 42 , wherein

the total of the radial lengths is equal to or larger than 10 mm.

44. The bicycle rear sprocket assembly according to claim 42 , wherein

the total of the radial lengths is equal to or larger than 15 mm.

45. The bicycle rear sprocket assembly according to claim 42 , wherein

the total of the radial lengths is equal to or smaller than 36 mm.

46. The bicycle rear sprocket assembly according to claim 42 , wherein

the total of the radial lengths of the plurality of internal-spline driving surfaces ranges from 11 mm to 14 mm.

47. The bicycle rear sprocket assembly according to claim 1 , wherein

at least one of the at least ten internal spline teeth includes

an internal-spline driving surface having a first internal-spline-surface angle defined between the internal-spline driving surface and a first radial line extending from a rotational center axis of the bicycle rear sprocket assembly to a radially outermost edge of the internal-spline driving surface, and

the first internal-spline-surface angle ranges from 0 degree to 6 degrees.

48. The bicycle rear sprocket assembly according to claim 47 , wherein

the at least one of the at least ten internal spline teeth includes

an internal-spline non-driving surface having a second internal-spline-surface angle defined between the internal-spline non-driving surface and a second radial line extending from the rotational center axis of the bicycle rear sprocket assembly to a radially outermost edge of the internal-spline non-driving surface, and

the second internal-spline-surface angle ranges from 0 degree to 6 degrees.

49. The bicycle rear hub assembly according to claim 1 , wherein

at least one of the at least ten internal spline teeth of the second sprocket is circumferentially symmetric with respect to a reference line extending from the rotational center axis to a circumferential center point of a radially outermost end of the at least one of the at least ten internal spline teeth in a radial direction with respect to the rotational center axis.

50. A bicycle drive train comprising:

the bicycle rear sprocket assembly according to claim 1 ; and

a bicycle rear hub assembly comprising:

a hub axle including an axle through-bore having a minimum inner diameter equal to or larger than 13 mm;

a hub body rotatably mounted on the hub axle about a rotational center axis of the bicycle rear hub assembly; and

a sprocket support body rotatably mounted on the hub axle about the rotational center axis.

51. The bicycle drive train according to claim 50 , wherein

the minimum inner diameter of the axle through-bore is equal to or larger than 14 mm.

52. The bicycle drive train according to claim 50 , wherein

the minimum inner diameter of the axle through-bore is equal to or smaller than 21 mm.

53. The bicycle rear sprocket assembly according to claim 1 , wherein

a total number of the at least ten internal spline teeth of the second sprocket ranges from 22 to 24.

54. A bicycle rear sprocket assembly configured to be mounted to a sprocket support body of a bicycle rear hub assembly, the bicycle rear sprocket assembly comprising:

a plurality of bicycle sprockets comprising:

a first sprocket including:

a first opening having a first minimum diameter that is smaller than a minimum outer diameter of the sprocket support body of the bicycle rear hub assembly; and

a second sprocket including:

a second opening having a second minimum diameter that is equal to or larger than the minimum outer diameter of the sprocket support body of the bicycle rear hub assembly; and

at least ten internal spline teeth configured to engage with the sprocket support body of the bicycle rear hub assembly; and

a lock member including:

a tubular body extending through the first opening of the first sprocket in a state where the bicycle rear sprocket assembly is mounted to the bicycle rear hub assembly, the tubular body including:

a first axial end; and

a second axial end opposite to the first axial end in an axial direction with respect to a rotational center axis of the bicycle rear sprocket assembly, the first axial end being positioned closer to an axial center plane of the bicycle rear hub assembly than the second axial end in the state where the bicycle rear sprocket assembly is mounted to the bicycle rear hub assembly;

a male thread portion provided to the first axial end to engage with a female thread portion of the sprocket support body of the bicycle rear hub assembly in the state where the bicycle rear sprocket assembly is mounted to the bicycle rear hub assembly; and

a radial projection extending radially outwardly from the second axial end with respect to the rotational center axis to restrict an axial movement of the first sprocket relative to the sprocket support body of the bicycle rear hub assembly in the state where the bicycle rear sprocket assembly is mounted to the bicycle rear hub assembly, wherein

the first sprocket includes:

a first inward facing side; and

a first outward facing side opposite to the first inward facing side in the axial direction,

the radial projection is configured to abut against the first sprocket in the first outward facing side, and

the lock member has a tool engagement portion.

55. A bicycle rear sprocket assembly configured to be mounted to a sprocket support body of a bicycle rear hub assembly, the bicycle rear sprocket assembly comprising:

a plurality of bicycle sprockets comprising:

a first sprocket including:

a first opening having a first minimum diameter that is smaller than a minimum outer diameter of the sprocket support body of the bicycle rear hub assembly; and

a second sprocket including:

a second opening having a second minimum diameter that is equal to or larger than the minimum outer diameter of the sprocket support body of the bicycle rear hub assembly; and

at least ten internal spline teeth configured to engage with the sprocket support body of the bicycle rear hub assembly, wherein

at least two internal spline teeth of the at least ten internal spline teeth of the second sprocket are circumferentially arranged at a first internal pitch angle with respect to a rotational center axis of the bicycle rear sprocket assembly,

the first internal pitch angle ranges from 5 degrees to 36 degrees,

at least other two internal spline teeth of the at least ten internal spline teeth of the second sprocket are circumferentially arranged at a second internal pitch angle with respect to the rotational center axis, and

the second internal pitch angle is different from the first internal pitch angle.

56. The bicycle rear sprocket assembly according to claim 55 , wherein

the second internal pitch angle ranges from 28 degrees to 32 degrees.

57. The bicycle rear sprocket assembly according to claim 55 , wherein

the first internal pitch angle is half of the second internal pitch angle.

58. A bicycle rear sprocket assembly configured to be mounted to a sprocket support body of a bicycle rear hub assembly, the bicycle rear sprocket assembly comprising:

a plurality of bicycle sprockets comprising:

a first sprocket including:

a first opening having a first minimum diameter that is smaller than a minimum outer diameter of the sprocket support body of the bicycle rear hub assembly; and

a second sprocket including:

a second opening having a second minimum diameter that is equal to or larger than the minimum outer diameter of the sprocket support body of the bicycle rear hub assembly; and

at least ten internal spline teeth configured to engage with the sprocket support body of the bicycle rear hub assembly, wherein

at least one of the at least ten internal spline teeth of the second sprocket has at least one of:

a first internal pitch angle different from a second internal pitch angle of another of the at least ten internal spline teeth;

a first spline shape different from a second spline shape of another of the at least ten internal spline teeth; and

a first spline size different from a second spline size of another of the at least ten internal spline teeth.