FIG. 6 is a front view showing a conventional fork end of a bicycle. In FIG. 6, numeral 1 denotes a fork end including cylindrical lugs 2 and 3 formed integrally in bifurcated ends thereof. These lugs 2 and 3 are fitted into each end of a back fork 8 and a chain stay 9, respectively, and fixed thereto by adhesives or soldering. The fork end 1 is formed at the tip thereof with a hole 4 for engaging a screw and through which a rear gearbox (not shown) is attached. Further, the fork end 1 is formed at the substantially center portion thereof with an engagement groove 5 having a downwardly inclining opening. A rod member 6 is engaged into the engagement groove 5 so that an end of the rod member 6 is projected sideways from the groove 5, and a hub shaft 7 is fitted onto the rod member 6. A hub (not shown) is rotatably mounted to the hub shaft 7 and a wheel, e.g., a rear wheel (not shown) is mounted to the hub through spokes. The rod member 6 engaged into the engagement groove 5 is moved axially by an operation of a quick lever (not shown) or nuts are engaged to the rod member 6 to hold the hub shaft 7 by the fork ends 1 between the nuts, so that the wheel is detachably mounted to the bicycle frame.
Where the engagement groove 5 is provided in the fork end 1, the mechanical strength in the proximity thereof is weakened. Similarly, the provision of the hole 4 also weakens the mechanical strength of the fork end tip. Accordingly, when an excessive force is experienced close to the engagement groove 5 through the wheel due to up and down movement of the bicycle in the running of the bicycle, or when an excessive force is exerted to the hole 4 through the rear gearbox due to falling-down of the bicycle, the portions of the fork end near the engagement groove 5 or the hole 4 may be deformed or broken (as shown by phantom lines A of FIG. 6).
As described above, the conventional fork end has the integral structure and includes the lugs 2 and 3 which are fixed to the back fork 8 and the chain stay 9 by adhesives or the like, respectively. Accordingly, when the proximity of the engagement groove 5 is deformed or broken, the conventional fork end 1 cannot be removed from the back fork 8 or the like and, hence, it is necessary to replace the whole frame of the bicycle and this is very expensive.
It has been considered that the thickness of the fork end 1 be made larger to enhance its mechanical strength, although the weight of the bicycle is then increased.