Our Traction Bars are designed to reduce rear fits Leaf spring axle wrap caused by lift blocks and oversized tires. Typically the travel cycle of the Super Duty rear axle is an arch. Fabtech's exclusive traction bar shackle system allows the bars to float with the arched travel of the rear axle. This provides a non-binding, smooth highway ride, while still providing positive resistance to torque loads, reducing axle wrap and increasing tire traction.