Motor vehicle drum brake including: - a fixed transversal plate; - a drum rotatably mounted with respect to the plate and equipped with a peripheral friction skirt; - two opposite braking segments (18A, 18B) including first transversally facing ends and second transversally facing opposite ends; - an anchoring element inserted transversally between the second ends of the braking segments (18A, 18B) such that each second end is elastically forced to pivotably transversally bear against an associated bearing surface (32A, 32B) of the anchoring element; - a wheel cylinder which, in a first so-called "simplex" operating mode of the drum brake, is suitable for transversally separating the two adjacent first ends of the braking segments (18A, 18B), pivoting the braking segments (18A, 18B) about the fixed bearing surface (32A, 32B) thereof with respect to the plate, to apply a friction surface surface of each braking segment (18A, 18B) against the friction skirt; the anchoring element including: - a fixed body with respect to the plate; - two pistons (50A, 50B) each carrying an associated bearing surface (32A, 32B) and which are slidably mounted transversally in the body, - characterised in that the anchoring element comprises: - controlled means for transversal separation of the bearing surfaces (32A, 32B) between an anchoring position wherein the pistons (50A, 50B) are clamped simultaneously against an associated abutment surface (48A, 48B) of the body by the associated segments (18A, 18B) to enable operation in "simplex" mode of the drum brake, the body acting as a fixed brace, and a sliding position wherein the bearing surfaces (32A, 32B) are separated from one another, the separating means acting as a sliding brace to enable rigidly connected and free sliding of the bearing pistons (50A, 50B) with respect to the fixed body during operation in so-called "servo-dual" mode of the drum brake. - a fixed transversal plate; - a drum rotatably mounted with respect to the plate and equipped with a peripheral friction skirt; - two opposite braking segments (18A, 18B) including first transversally facing ends and second transversally facing opposite ends; - an anchoring element inserted transversally between the second ends of the braking segments (18A, 18B) such that each second end is elastically forced to pivotably transversally bear against an associated bearing surface (32A, 32B) of the anchoring element; - a wheel cylinder which, in a first so-called "simplex" operating mode of the drum brake, is suitable for transversally separating the two adjacent first ends of the braking segments (18A, 18B), pivoting the braking segments (18A, 18B) about the fixed bearing surface (32A, 32B) thereof with respect to the plate, to apply a friction surface surface of each braking segment (18A, 18B) against the friction skirt; - a fixed body with respect to the plate; - two pistons (50A, 50B) each carrying an associated bearing surface (32A, 32B) and which are slidably mounted transversally in the body, - characterised in that the anchoring element comprises: - controlled means for transversal separation of the bearing surfaces (32A, 32B) between an anchoring position wherein the pistons (50A, 50B) are clamped simultaneously against an associated abutment surface (48A, 48B) of the body by the associated segments (18A, 18B) to enable operation in "simplex" mode of the drum brake, the body acting as a fixed brace, and a sliding position wherein the bearing surfaces (32A, 32B) are separated from one another, the separating means acting as a sliding brace to enable rigidly connected and free sliding of the bearing pistons (50A, 50B) with respect to the fixed body during operation in so-called "servo-dual" mode of the drum brake. - controlled means for transversal separation of the bearing surfaces (32A, 32B) between an anchoring position wherein the pistons (50A, 50B) are clamped simultaneously against an associated abutment surface (48A, 48B) of the body by the associated segments (18A, 18B) to enable operation in "simplex" mode of the drum brake, the body acting as a fixed brace, and a sliding position wherein the bearing surfaces (32A, 32B) are separated from one another, the separating means acting as a sliding brace to enable rigidly connected and free sliding of the bearing pistons (50A, 50B) with respect to the fixed body during operation in so-called "servo-dual" mode of the drum brake.