A drug delivery device comprising or being adapted to receive a cartridge, the cartridge comprising a cylindrical body portion, an axially displaceable piston, and a distal outlet portion, the drug delivery device comprising: - a housing, - an expelling assembly adapted to axially move the piston of a cartridge to thereby expel a dose of drug, comprising: - a piston rod adapted to engage and axially displace a piston in a cartridge in a distal direction to thereby expel a dose of drug from the cartridge, - a drive spring which in an energized state is adapted to drive the expelling assembly, - a rotating component (550, 650) adapted to rotate relative to an axis of rotation during expelling of a dose of drug, the rotating component being in the form of a drive member (550, 650) adapted to be rotated by the strained drive spring to thereby move the piston rod in the distal direction, and - user actuated release means (181, 290) for releasing the drive spring to thereby expel a dose of drug, the device further comprising: - a brake element (575, 675) adapted to engage the rotating component such that during rotation thereof the brake element is moved back and forth by the rotating component, whereby the brake element provides a braking action on the rotating component, - a guide structure (548, 648) adapted to engage the brake element(s) to thereby guide the brake element(s) corresponding to the back and forth movement, and - an engagement structure for engaging the brake element(s) during rotation, the engagement structure comprising one or more serrated surface structures (558, 559, 658, 659), characterized in that - the brake element (575, 675) is moveable in a plane perpendicular to the axis of rotation, - the brake element is arranged non-rotational relative to the housing, - the one or more serrated surface structures (558, 559, 658, 659) is/are radially oriented, - the guide structure (548, 648) is non-rotational, and - the rotating component (550, 650) comprises the engagement structure. - a housing, - an expelling assembly adapted to axially move the piston of a cartridge to thereby expel a dose of drug, comprising: - a piston rod adapted to engage and axially displace a piston in a cartridge in a distal direction to thereby expel a dose of drug from the cartridge, - a drive spring which in an energized state is adapted to drive the expelling assembly, - a rotating component (550, 650) adapted to rotate relative to an axis of rotation during expelling of a dose of drug, the rotating component being in the form of a drive member (550, 650) adapted to be rotated by the strained drive spring to thereby move the piston rod in the distal direction, and - user actuated release means (181, 290) for releasing the drive spring to thereby expel a dose of drug, - a piston rod adapted to engage and axially displace a piston in a cartridge in a distal direction to thereby expel a dose of drug from the cartridge, - a drive spring which in an energized state is adapted to drive the expelling assembly, - a rotating component (550, 650) adapted to rotate relative to an axis of rotation during expelling of a dose of drug, the rotating component being in the form of a drive member (550, 650) adapted to be rotated by the strained drive spring to thereby move the piston rod in the distal direction, and - user actuated release means (181, 290) for releasing the drive spring to thereby expel a dose of drug, - a brake element (575, 675) adapted to engage the rotating component such that during rotation thereof the brake element is moved back and forth by the rotating component, whereby the brake element provides a braking action on the rotating component, - a guide structure (548, 648) adapted to engage the brake element(s) to thereby guide the brake element(s) corresponding to the back and forth movement, and - an engagement structure for engaging the brake element(s) during rotation, the engagement structure comprising one or more serrated surface structures (558, 559, 658, 659), - the brake element (575, 675) is moveable in a plane perpendicular to the axis of rotation, - the brake element is arranged non-rotational relative to the housing, - the one or more serrated surface structures (558, 559, 658, 659) is/are radially oriented, - the guide structure (548, 648) is non-rotational, and - the rotating component (550, 650) comprises the engagement structure.