Device comprising an adjusting device provided at least at one end of a bowden cable for transmitting a grasping force on a brake operating lever in a direction to actuate brake shoes. The adjusting device includes a gauge member having a bore for passing the inner element of the cable therethrough and a hole or recess formed at one end of the bored portion and having a depth to determine a proper brake clearance, a nut having a portion shaped to fit in the recess of the gauge member and a portion of a shape unfittable in the recess when turned through a desired angle, and an adjusting screw member screwed in the nut and connected to the outer element of the cable. While the nut is disengaged from the recess of the gauge member, the adjusting screw member is advanced on the nut in screw-thread engagement therewith until the ends of the brake shoes come into contact with the rim and, after the brake shoes contact the rim, the nut is fitted into the recess of the gauge member to thereby give the proper brake clearance.