When a rear leaf spring equipped vehicle launches off the line, the torque of the rear axle tries to torque the front leaf spring mount upward and the rear leaf spring mount downward. As this happens, the leaf spring takes on a slight S-shape. This causes wheel hop and loss of traction. Pinion yoke to driveshaft angle will also change under launch and can cause driveline problems. Traction bars eliminate wheel hop and driveline angle problems during launch. Traction bars, or lift bars, are available for coil spring vehicles too. While coil spring lift bars work in a different way than leaf spring traction bars, you still get added traction by moving more vehicle weight onto the rear tires.