track bar can help a too tight or too lose condition and yeah it can help with a bad setup, both with adjustments in the pits and being able to fine tune it out on the track. If you raise the trackbar on the right-hand side, you move the rear wheels to the right. This makes the car looser when accelerating and tighter when braking. Conversely, moving the trackbar down on the right-hand side pushes the wheels to the left, tightening the car under acceleration and loosening the car during braking. Moving the rear axle left/right is essentially adding stagger (“rear steer”) to the car because the distance between the front and rear wheels isn’t the same on both sides of the car due to the offset.