A door closer or operator, comprising: a door closer or operator housing adapted to be mounted to one of a door frame or a door; a pivoting pinion on the door closer housing for transmitting door motion between the door closer housing and the other of the door or door frame; a cam connected to the pinion and rotatable therewith about an axis of rotation, the cam having a peripheral edge about the axis of rotation; a coil spring having two ends and a central opening along a longitudinal axis thereof, with a first end secured to the door closer housing; a connecting member secured to the spring adjacent a second end thereof to compress the spring, the connecting member extending along the spring from the spring second end to a position beyond the spring first end where the connecting member is tangential to and engages the peripheral edge of the cam, rotation of the cam causing a change in length of the portion of the connecting member between the position tangent to the cam peripheral edge and the spring second end to expand or compress the spring, resulting in a force transmitted along a longitudinal axis of the connecting member as a result of spring deflection, the cam peripheral edge having a profile with a varying radial distance between the cam axis and the connecting member at the position tangent to the cam peripheral edge such that the radial distance is changed as the spring expands or compresses to maintain a desired torque about the axis of the cam and the connected pinion; and a sleeve extending within the spring central opening and having an open end secured to the spring first end, the sleeve being disposed between the spring and the connecting member. a door closer or operator housing adapted to be mounted to one of a door frame or a door; a pivoting pinion on the door closer housing for transmitting door motion between the door closer housing and the other of the door or door frame; a cam connected to the pinion and rotatable therewith about an axis of rotation, the cam having a peripheral edge about the axis of rotation; a coil spring having two ends and a central opening along a longitudinal axis thereof, with a first end secured to the door closer housing; a connecting member secured to the spring adjacent a second end thereof to compress the spring, the connecting member extending along the spring from the spring second end to a position beyond the spring first end where the connecting member is tangential to and engages the peripheral edge of the cam, rotation of the cam causing a change in length of the portion of the connecting member between the position tangent to the cam peripheral edge and the spring second end to expand or compress the spring, resulting in a force transmitted along a longitudinal axis of the connecting member as a result of spring deflection, the cam peripheral edge having a profile with a varying radial distance between the cam axis and the connecting member at the position tangent to the cam peripheral edge such that the radial distance is changed as the spring expands or compresses to maintain a desired torque about the axis of the cam and the connected pinion; and a sleeve extending within the spring central opening and having an open end secured to the spring first end, the sleeve being disposed between the spring and the connecting member.