There is a design for a three-link rear end that utilizes the motion of a pullbar. The LR spring is mounted in front of the rear end and the RR spring is mounted behind the rear end. When the car accelerates and the rear end rotates as the pullbar extends, the LR spring compresses and the RR spring decompresses. This adds load to the LR wheel and takes load off the RR wheel. This usually causes the rear tires to be more equally loaded, and the car will have more traction to help provide better bite off the corners.