| 摘要 |
PROBLEM TO BE SOLVED: To prevent deterioration in braking force during running in rainy weather by improving foreign material intrusion preventive effect into a drum. SOLUTION: A projection streak 18 is formed on an intermediate portion of an outer peripheral surface of a cylindrical part 11 of a drum 10 over its circumference. Two grooves 19, 20 are formed on an outer peripheral surface on the side of an opening end compared to the projection streak, respectively over the circumference. Peripheries of the grooves 19, 20 are surrounded by a coating plate 23 formed on an outer peripheral edge of a back plate 1. A front edge of the coating plate 23 is opposed to a side surface of the projection streak 18 in the vicinity thereof.
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