A roller shade having a counterbalancing assembly with an optimally pretensioned spring that lowers the torque load on the motor of the roller shade throughout the rolling up or rolling down cycles. The roller shade comprises a roller tube, a gudgeon pin having a first stop, a gudgeon body having a through bore and rotatably connected about the gudgeon pin and operably connected to the roller tube, a limit nut operably connected to the gudgeon body and adapted to axially travel along the gudgeon pin within the through bore, a spring, a first spring carrier connected to the first end of the spring and operably connected to the gudgeon pin, and a second spring carrier connected to the second end of the spring and operably connected to the roller tube. The spring is pretensioned and the limit nut abuts the first stop thereby locking the pretension. Rotation of the roller tube to roll down the shade further tensions the spring, and rotation of the roller tube to roll up the shade releases the tension in the spring.