A bicycle sprocket arrangement comprises an internal spline configured to be engaged with an external spline of a sprocket support body of a bicycle hub assembly. The internal spline includes a plurality of internal-spline driving surfaces configured to transmit a rotational driving force between the bicycle sprocket arrangement and the bicycle hub assembly in a circumferential direction. The plurality of internal-spline driving surfaces includes at least four first internal-spline driving surfaces and at least one second internal-spline driving surface. The at least four first internal-spline driving surfaces are respectively arranged on at least four of nine first internal-spline driving positions equally arranged in the circumferential direction about a rotational center axis at a first internal-spline pitch angle which is equal to 40 degrees. The at least one second internal-spline driving surface is offset from the nine first internal-spline driving positions in the circumferential direction about the rotational center axis.

A bicycle sprocket arrangement comprises an internal spline configured to be engaged with an external spline of a sprocket support body of a bicycle hub assembly. The internal spline includes a plurality of internal-spline driving surfaces configured to transmit a rotational driving force between the bicycle sprocket arrangement and the bicycle hub assembly in a circumferential direction. The plurality of internal-spline driving surfaces includes at least four first internal-spline driving surfaces and at least one second internal-spline driving surface. The at least four first internal-spline driving surfaces are respectively arranged on at least four of nine first internal-spline driving positions equally arranged in the circumferential direction about a rotational center axis at a first internal-spline pitch angle which is equal to 40 degrees. The at least one second internal-spline driving surface is offset from the nine first internal-spline driving positions in the circumferential direction about the rotational center axis.

An in-wheel motor unit provided in a wheel of a wheel unit, includes: a motor having a rotor disposed on a radially outer side of a stator; a brake disposed on an inner side of the motor; and a housing that accommodates the motor and the brake. Further, the housing has a cylindrical partition that radially partitions a space for accommodating the motor and a space for accommodating the brake, the stator is fixed to an outer peripheral surface of the partition, and the brake is disposed on an inner peripheral side of the partition, and a fixing portion included in the brake is fixed to the housing.

An in-wheel motor unit provided in a wheel of a wheel unit, includes: a motor having a rotor disposed on a radially outer side of a stator; a brake disposed on an inner side of the motor; and a housing that accommodates the motor and the brake. Further, the housing has a cylindrical partition that radially partitions a space for accommodating the motor and a space for accommodating the brake, the stator is fixed to an outer peripheral surface of the partition, and the brake is disposed on an inner peripheral side of the partition, and a fixing portion included in the brake is fixed to the housing.

The disclosure refers to a hub for a bicycle running wheel, a bicycle drive system and a bicycle. In an embodiment a hub for a bicycle running wheel includes a hub body and a receiving area configured to receive a force transmission means, wherein the hub body and the receiving area are a single part or are firmly connected together.

A bicycle rear wheel adapter has an annular body that abuts a sprocket-carrying body that extends in an axially outer direction and receives sprockets in radially peripheral positions. A coupling element on the annular body couples with the sprocket-carrying body so the adapter rotates as a unit with the sprocket-carrying body, and a sprocket-receiving seat on the annular body couples with a sprocket so the adapter rotates as a unit with the sprocket. The adapter is suitable for cogsets with small sprockets grouped in a monolithic grouping.

A bicycle rear wheel adapter has an annular body that abuts a sprocket-carrying body that extends in an axially outer direction and receives sprockets in radially peripheral positions. A coupling element on the annular body couples with the sprocket-carrying body so the adapter rotates as a unit with the sprocket-carrying body, and a sprocket-receiving seat on the annular body couples with a sprocket so the adapter rotates as a unit with the sprocket. The adapter is suitable for cogsets with small sprockets grouped in a monolithic grouping.

A bicycle transmission device for connecting to a freehub body on a rear wheel, which has convex keys arranged radially on the periphery. The bicycle transmission device includes a connecting member, a fastener, and a cogset assembly. The connecting member includes a cylindrical body portion, connection keys protruding from a periphery of the body portion, a cut groove passing through the body portion, and first and second connecting seats located on two sides of the cut groove. The inner wall of the body portion has concave grooves corresponding to the convex keys. The fastener is adapted to be connected to the connecting seats and to pull them together. The cogset assembly includes a cogset seat and sprockets. The cogset seat has a first socket hole fitting around the connecting member and connection grooves corresponding to and adapted to be connected to the connection keys. The sprockets with different numbers of chain teeth are adapted to be connected to the cogset seat.

A bicycle transmission device for connecting to a freehub body on a rear wheel, which has convex keys arranged radially on the periphery. The bicycle transmission device includes a connecting member, a fastener, and a cogset assembly. The connecting member includes a cylindrical body portion, connection keys protruding from a periphery of the body portion, a cut groove passing through the body portion, and first and second connecting seats located on two sides of the cut groove. The inner wall of the body portion has concave grooves corresponding to the convex keys. The fastener is adapted to be connected to the connecting seats and to pull them together. The cogset assembly includes a cogset seat and sprockets. The cogset seat has a first socket hole fitting around the connecting member and connection grooves corresponding to and adapted to be connected to the connection keys. The sprockets with different numbers of chain teeth are adapted to be connected to the cogset seat.

A hub assembly is provided for a human-powered vehicle. The hub assembly includes a hub axle, a hub body, a bearing spacer and a first hub body bearing. The hub body is rotatably mounted on the hub axle to rotate around a rotational center axis of the hub assembly. The bearing spacer has an inner peripheral end provided to the hub axle and an outer peripheral end spaced radially outward of the inner peripheral end in a radial direction with respect to the rotational center axis. The first hub body bearing is disposed at the outer peripheral end of the bearing spacer and rotatably supporting the hub body.