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Do-It-Yourself Projects
Leaf Spring Restoration
By Iain Ayre/
Printable version
Degree of DifficultyDifficult
Estimated Time240 minutes
240 minutes
How to Turn Over an Old Leaf -
Everything tends to get saggy with old age, some things need repairs while others need replacement. Leaf springs, fortunately, can be repaired rather than replaced. This common type of suspension is commonly seen under various types of vehicles with straight- or live-axle rear ends. For this particular restoration, we'll focus on an older Jeep Grand Wagoneer.
Leaf Spring Restoration
It takes some effort for a set of springs to hold up a Wagoneer for 20 years or so, and by last year these leaf springs were getting so saggy they were almost flat. Springs don't actually lose tension and become less springy, but they do rust away and become less strong as a result of supporting a great deal of weight over a long period of time. They can also get bent, particularly if the driver indulges in off-road fun.

These springsare 20 years old and have seen over 120,000 miles of abuse, so finding flat and broken leaves was no surprise.

Some Leaves in These 20-Year-Old Springs Are Flat or Broken
Steel Base
There are two options for handling worn out leaf springs. They can be replaced, which can be pretty expensive for a set of four, or they can get overhauled, which is not too expensive. If you would rather not do the repairs on your own, look for a shop that specializes in springs and lift kits for trucks and off-roaders. One thing to bear in mind is that it might be easier to just cut off the nuts and bolts securing the springs if they've been connected for several years. If you want to remove eight ancient spring shackle nuts and bolts yourself, you're looking at some major wrench action and a few cans of lubricant.
This Wagoneer's springs were in pretty bad condition, with a few leaves snapped and all of them bent out of shape. The shop technicians disassembled them one at a time, then straightened out the bent leaves on a press, and made a few new leaves for replacing those that were broken. There was nothing high-tech about it. The shop had a supply of spring steel that the technician cut and trimmed to the right length. The spring was reassembled with a mix of old and new leaves.
Fall to Spring
After many years of making and repairing springs, an experienced shop technician can tell from looking at them how much bending leaf springs will need to get straightened out. When the springs are put together, the shop technician can check them for the correct shape by putting a steel bar across the ends and measuring the spring height, although he or she will probably have a pretty good idea of what they should look like without measuring them. This seems an uncanny ability, but on a factory visit to Eibach's modern spring factory in Germany, we were introduced to a chap who still winds dual-rate Formula 1 racing cars springs by hand, and who is quicker and more accurate than a computer—just through hand-eye coordination, and years of experience.

A hydraulic press re-bends the springs, in a gentle curve, back to their original shapes. It takes a few years of experience to judge where and how to apply the force.

Hydraulic Press Rebends Springs Back to Original Curve
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