The present invention relates to brakes mounted in particular on all terrain bicycles. It relates, as to the first embodiment, to a brake comprising identical arms (17) mounted freely in rotation on trunnions, carrying for each of the arms (17) at its upper portion a hollow V shaped cam (23) pierced at its middle, the angle of the dihedral of about 90, the bisecting edge horizontal, which receives a pin (9) carrying a cam finger (21) which acts against the cam (23) to close the brake. The pin (9) is secured to the end (3) of the movable arch (1) which controls the action of the brake with a movement of rotation from holes (4, 5) located in the upper central portion of the arch (1). Compression springs (26) disposed about pins (9) ensure the holding and return of the arms (17) into position.