1. Field of the Invention
The invention relates to a bicycle wheel rim, more particularly to a bicycle wheel rim having a braking plate projecting integrally from a main rim body of the wheel rim to be contacted by brake pads of a brake device in order to prevent deformation of the main rim body due to frequent braking while maintaining a relatively good braking effect.
2. Description of the Related Art
FIG. 1 illustrates a conventional bicycle wheel with a wheel rim 1 which includes a pair of spaced-apart tire retaining walls 12 adapted for retaining a bicycle tire 10 therebetween, and an annular spoke mounting wall 11 interconnecting radial inner edges of the tire retaining walls 12. The spoke mounting wall 11 is adapted for mounting a plurality of spokes 13 thereon so as to mount the wheel rim 1 on a hub 14 to form a bicycle wheel. The bicycle wheel is then mounted on a front/rear fork 16 of a bicycle frame by means of an axle 15 extending through the hub 14. The tire retaining walls 12 have brake pad contacting surfaces 121 at opposite lateral outer sides thereof to be contacted by brake pads 17 of a caliper brake device. When the brake device is operated while the bicycle wheel is in motion, the wheel rim 1 is clamped by the brake pads 17 at the tire retaining walls 12 to resist movement of the bicycle wheel. Therefore, after the bicycle wheel is in use for a period of time, the wheel rim 1 is susceptible to deformation due to frequent clamping by the brake pads 17, and might be worn by the brake pads 17, thereby reducing the strength of the wheel rim 1.
To solve the aforementioned problems, a disk brake has been proposed in the art. Referring to FIG. 2, a disk brake 21 is mounted on a lateral side of the hub 14 by means of screw bolts 20 such that the disk brake 21 is co-rotatable with the bicycle wheel. A brake device 22 is mounted on the front/rear fork 16 for contacting the disk brake 21. When the brake device 22 is operated, the disk brake 21 is clamped tightly by two brake pads 23 of the brake device 22. However, since the radial distance between the brake pads 23 and the axle 15 is much smaller that the radial distance between the tire retaining walls 12 and the axle 15, the torque generated by the brake pads 23 when clamping on the disk brake 21 is smaller than that when the brake pads clamp the tire retaining walls 12. Thus, the braking effect achieved when the disk brake 21 is in use is unsatisfactory.