An apparatus including a bicycle frame including a drive side chain stay. The drive side chain stay can include a drive side chain stay chamber, an inside chain stay cutout, an outside chain stay cutout; and a dropout. The drive side chain stay can be configured such that a chain of a bicycle including the bicycle frame can be inserted through the inside chain stay cutout, the drive side chain stay chamber, and the outside chain stay cutout without breaking the chain.

An apparatus including a bicycle frame including a drive side chain stay. The drive side chain stay can include a drive side chain stay chamber, an inside chain stay cutout, an outside chain stay cutout; and a dropout. The drive side chain stay can be configured such that a chain of a bicycle including the bicycle frame can be inserted through the inside chain stay cutout, the drive side chain stay chamber, and the outside chain stay cutout without breaking the chain.

An apparatus including a bicycle frame including a drive side chain stay. The drive side chain stay can include a drive side chain stay chamber, an inside chain stay cutout, an outside chain stay cutout; and a dropout. The drive side chain stay can be configured such that a chain of a bicycle including the bicycle frame can be inserted through the inside chain stay cutout, the drive side chain stay chamber, and the outside chain stay cutout without breaking the chain.

A bicycle includes a frame having four bar elements, wherein the first bar element is pivotally connected to the second bar element by a first hinge, the second bar element is pivotally connected to the third bar element by a second hinge, the third bar element is pivotally connected to the fourth bar element by a third hinge and the fourth bar element is pivotally connected to the first bar element by a fourth hinge, a front axle protruding from the third bar element for mounting a front wheel, a rear axle protruding from the first bar element for mounting a rear wheel, wherein the fourth hinge is disposed rear of the rear axle, at least one handlebar attached to the third bar element.

A front assembly for use with a rear module to form a riding vehicle is disclosed. The front assembly includes an elongate frame, a mount disposed beneath the elongate frame, a head assembly with a front wheel and handlebar, and a seat mounted relative to the elongate frame. The elongate frame terminates in two laterally spaced apart prongs removably securable to connectors of the rear module. The connectors and elongate frame together constitute a bicycle frame. The riding vehicle may be convertible between different configurations, such as a balance bicycle and a pedal bicycle, by interchanging rear modules. The rear modules may have different wheel sizes and connector geometries while maintaining compatibility with the front assembly. The riding vehicle may include features for partially encasing the mount in different configurations and may be foldable for compact storage.