Brake pad in an axle disc brake A, the pad comprising a shoe (1) and a lining made from friction material, the lining being defined by a friction face (26), a mounting face (20), an internal edge (23), an external edge (24), a front edge (21), a rear edge (22), the lining being provided with a collection groove (3), open on the friction face (26) and arranged close to the front edge (21), the shoe comprising a hole (17) in fluid communication with the collection groove, this hole being connected to a vacuum source via the communication means (4), the collection groove emerging at one of the edges chosen among the internal and external edges.