One of the most obvious indicators that your leaf springs are worn is when cracks appear on the leaves. However, it's not always easy to tell when springs are worn, because the visible evidence is often hard to spot. Another indicator of bad springs is when the truck sags downward in back, which can cause the rear tires to flatten and point the headlights upward. Then again, your truck could have bad leaf springs even if the truck itself remains in a perfectly horizontal position. This is due to the design of certain trucks, which are actually built with a slight lift in back to accommodate excess weight that could otherwise cause dipping.