Abstract: In a bicycle frame comprising a plurality of tubes having hollow ends and a plurality of fittings having pins fitting in the hollow ends, each pin extends along an axis and has an outer surface portion of axially constant section centered on the axis and engaged in the respective tube end, an inner surface portion centered on the axis and flaring axially inward away from the inner end of the respective outer surface portion, and a shoulder surface projecting generally perpendicular from the inner end of the respective inner surface portion and facing outward. Each tube end has an end surface abutting flatly inward on the respective shoulder surface and an inner surface having an inner surface portion fitted tightly over and complementary to the inner surface portion of the respective pin and an outer surface portion radially slightly spaced from and facing the outer surface portion of the respective pin.