Spinning rotor assembly for a rotor spinning machine, comprising - a spinning rotor fixed to a spinning rotor shaft, the spinning rotor shaft being rotatably mounted to a housing of the spinning rotor assembly by at least one bearing unit, wherein the housing has two parts pivotably mounted to one another, wherein the first part is fixed to the at least one bearing unit and the second part is arranged pivotally relative to the spinning rotor, - wherein the spinning rotor assembly is pivotally mounted about a pivoting joint between a first, closed position for operating the spinning rotor and a second open position, where the spinning rotor is accessible, wherein in the first position, the first and second part of the housing are in contact to form a closed housing, wherein in the second position, the first and second part of the housing are not in contact to provide an opening to access the spinning rotor, - wherein a rotor brake for braking the spinning rotor is pivotally mounted to the housing, so that the rotor brake is built to automatically engage when the spinning rotor assembly is moved from the first to the second position and to be automatically released when the spinning rotor assembly reaches the closed position, - wherein the rotor brake comprises a brake lever pivotally mounted via a pivot axle to the housing, wherein on one side of the brake lever the braking surface is located and on the other side of the brake lever, a spring element is provided to apply force to the brake lever towards an engaged position of the rotor brake, characterized in that the brake lever is divided into two sides by the pivot axle, the first side being an actuation side on which the spring element is arranged and the second side being a braking side on which the braking surface is provided, wherein the pivot axle of the brake lever and the pivoting axis of the two housing parts are arranged in parallel. - a spinning rotor fixed to a spinning rotor shaft, the spinning rotor shaft being rotatably mounted to a housing of the spinning rotor assembly by at least one bearing unit, wherein the housing has two parts pivotably mounted to one another, wherein the first part is fixed to the at least one bearing unit and the second part is arranged pivotally relative to the spinning rotor, - wherein the spinning rotor assembly is pivotally mounted about a pivoting joint between a first, closed position for operating the spinning rotor and a second open position, where the spinning rotor is accessible, wherein in the first position, the first and second part of the housing are in contact to form a closed housing, wherein in the second position, the first and second part of the housing are not in contact to provide an opening to access the spinning rotor, - wherein a rotor brake for braking the spinning rotor is pivotally mounted to the housing, so that the rotor brake is built to automatically engage when the spinning rotor assembly is moved from the first to the second position and to be automatically released when the spinning rotor assembly reaches the closed position, - wherein the rotor brake comprises a brake lever pivotally mounted via a pivot axle to the housing, wherein on one side of the brake lever the braking surface is located and on the other side of the brake lever, a spring element is provided to apply force to the brake lever towards an engaged position of the rotor brake,