Understanding Spring Failure
[Leaf] Click to Return to Leaf Spring Page
The first fact that needs to be considered when attempting the diagnosis of a spring, suspension or steering problem is to understand that a suspension is considered a system. Like the system you are currently using to view this page, it requires the correct operation of a number of components rather that just one for effective operation. What am I saying? The spring relies on busings to maintain vehicle alignment, the spring relies on the ubolts to position the spring to the axle correctly. The ball joints require the control arm bushings be of good condition in order to perform correctly. In other words, a complete survey of the suspension needs to be completed before deciding on what component to replace. On countless situations, we find parts having been replaced when in fact the problem has been another component. Not only is this expensive, but can be dangerous.

Let me explain. It is common to have a vehicle with a pull. Now a pull is when your vehicle continually wants to turn in one direction or another. A pull is usually caused by an alignment problem. But countless steering boxes have been sold to repair a pulling problem. Now it gets tricky... A new steering box can reduce the amount of a pull due to the fact that the box itself is in new condition and does not have the looseness that an older steering box may have. The new steering box, being new, will have improved efficiency or power generating ability and temporarily pull can be reduced. The pull will return due to the fact that the fundamental problem is alignment.

If you have experienced a spring failure, and the cause is not easily detected (like a wreck or something), then before you quickly replace it, try to understand why it failed. Maybe you can circumvent it's failure again. Now if your spring is 30 years old and has 150,000 miles then I expect that old age has a lot to do with it, however, if you feel that your springs or suspension has failed prematurely, I will discuss some common problems.

Lean
Probably the most common suspension complaint is a leaning vehicle. Typically the lean is being caused by the spring bending more, hence the lean, although spring may not be the cause. Let's think about this. The spring responds to weight by bending, the more weight the more bend. See where I'm going? If a vehicle has a weight imbalance, then the car or truck will lean. I guarantee it. Now although you would think that any car or truck is balanced left to right, it's not. In the USA, all cars and trucks have a steering system, braking system and a driver that is predominately on the "drivers" side, on top of this add fuel tanks and other loads and it is easy to see that a vehicle is not perfectly balanced, it can't be.

Now it may seem trivial to think that 150-200 pounds (plus the driver) won't make a difference, but over time, due to the fact that one spring is continually working harder than the other, it will fatigue or weaken at a different rate than the other and hence lean.

Sag
Number 2 on the spring problem hit parade, Sag. Fatigue is a fact of life, the more we work the more tired we become. Consider a spring, a spring will be designed for certain number of cycles, deflections, movements or whatever you want to call it. Now when a spring reaches that point it has achieved its design life. What's wrong, maybe it's too soon though.

Spring life is a function of how hard it works. If a spring is designed to let's say hold up a car with a 3000 lb. maximum weight, and the car still weighs under 3000 lbs, then the spring is operating within its design guidelines. It sould last as long as the car is intended. What happens when that same car is 300 lbs heavier than the springs were designed? The springs that were designed for 3000 lbs are now trying to hold up 3300lbs. As we have gone beyond the design load, we have shortened the cycle life, those springs are now fatiguing faster.

Broken Center Bolt
You may have been driving one day and seen a vehicle, car or truck, that looks like it is going down the road "sideways". This is an alignment problem in the back of the vehicle, or "rear steer". This can be caused by a number of problems from broken attaching parts, broken springs or commonly a broken center bolt.

The center bolt is a small bolt that performs two functions, first it holds the spring together prior to installation (that prior part is important), and secondly to locate the axle (if spring over axle suspension) for installation. After installation though, it is the job of the UBolts to hold the axle in place. Broken center bolt?, Bad Ubolts. Replace them.

Broken Leafs
Consider a broken leaf. A broken leaf within a spring may have many causes but a few rules apply.
Rear Axle Mis-Alignment
Commonly refered to as "Dog Tracking", rear axle mis-alignment can be caused by a number of factors but initial analysis needs to be directed to the following areas If you are concerned about why your suspension system has failed, please feel free to email or call me and I will be happy to talk to you about it. Understand though, it is very important to be able to inspect it.

[Home] Click to Return to Benz Spring Home Page
If you have any comments, please address or click here to: kbenz@benzspg.com Benz Spring Co
700 S Forest St
Seattle WA 98134
206-624-7733

This information is presented by Benz Spring Co for the sole use of our customers to assist in the diagnosis of leaf spring problems. This document is not intended to replace a good mechanic and represents a compilation of real life experiences in the troubleshooting of suspension systems. However, the individual designs may validate or invalidate this information so consult an experienced mechanic for any additional difficulties. This page is copyrighted by Benz Spring Co 1995.