When the car sags to one side or in the back then it might be an indication that you need to re-arch your leaf springs. This kind of sagging affects the appearance of the vehicle and can also interfere with handling, steering, or braking. It can be difficult to undertake this process on your own, but with the right tools, it is possible.
The leaf springs will also need rebuilding after they're re-arched. This involves replacing all the parts, as it is not advised to re-use any of the old components. Make sure that the new parts are an exact match for the type of vehicle being repaired.
How to Re-arch
There are two methods used to re-arch leaf springs. The most common is cold pressing which uses a special press to change the arch. This offers a short term solution to the problem as the steel leaf springs have a memory which easily returns them to the height they were before being raised. As such, it is highly advisable not to re-arch using cold setting.
Heat treating involves erasing the spring’s memory by annealing and then re-shaping. Heat treatment is used on each leaf in turn before they are reassembled and re-installed.
This process uses special equipment. The spring is first clamped in a hydraulic clamp to dissemble its components. Then, each leaf is laid across arbors and a hydraulic press pushes it down between the blocks. Pressure is fully applied across each leaf at a 90-degree angle to its length. This is done from one end to the other, moving across different points on its surface. Pressure is applied until the entire length of the leaf is covered, and a rhythm is developed to ensure even application of pressure, as applying too much in any one area can easily break a leaf. This process re-arches each leaf separately.
To finish re-arching using this process, spring leafs are re-assembled in their original position while the technician tries to get the same orientation using new center bolts and tie clamps.
The material used to manufacture spring steel has a memory that makes it return to its shape. In this process, the spring is first taken apart and a technician inspects it for damage or wear and tear. Then, rust, corrosion, paint, and any other kind of finishing is removed from the surface by blasting, and they are re-inspected. If they are still in good condition, each leaf is heated to at least 1650 degrees Fahrenheit to be re-shaped. While malleable, the spring is patterned using the correct shape and arch before being placed in a special oil to cool it. The spring is then re-heated to at least 950 degrees Fahrenheit to set it to the correct hardness.
Re-installing Leaf Spring
After reforming the leaf springs, the final product is well-tempered, arched, and shaped. Then, they can be re-installed in their proper place.