Dec 6th 2020
How Long Will Your Leaf Springs Last?
For a lot of truck owners, broken leaf springs symptoms seem difficult to spot. However, this is only because they likely haven't paid attention to this very crucial part of a vehicle.
Inspecting a truck for evidence of a broken leaf spring or two is actually quite easy once you know how to identify the truck's proper behaviors. When you learn how to tell bad leaf springs apart from good ones, learning how to repair leaf springs as well as maintain them will become a lot easier.
While some of the symptoms of broken leaf springs are readily apparent, others are less obvious and can only be detected with knowledge of how the springs should look and perform.
HOW LONG DO LEAF SPRINGS LAST?
Is there a rule of thumb for when to replace leaf springs? Like any other part of a vehicle, it depends. The life span of leaf springs can vary based on several factors, including how old the vehicle is and how often you use it — plus road conditions and environmental circumstances. In an older, heavily driven automobile, the leaf springs may not last as long.
In contrast, a well-maintained vehicle's leaf springs can last well over 100,000 miles. On average, a set of leaf springs might last about 200,000 miles. This number can range widely from case to case — it's hard to say how long your leaf springs will last in your unique situation. Keep your eyes and ears peeled for symptoms of wear and tear. Rather than strictly sticking to a maintenance schedule, watch for visible signs of when to repair leaf springs as well. Learn how to tell if they're broken, worn, loosened or dirty.
What You Might Notice If the Leaf Springs Are Broken
When rear springs are broken, it's often easy to tell by looking at the leaves and spotting the cracks and fractures. However, you'd need to get under the truck to perform that type of inspection.
From the outside of the truck, one of the easiest ways to tell if you have bad leaf springs is by studying how the vehicle sits from a side-view when parked and empty. Is the truck vertical from front to back, or does it appear slouched or elevated at the rear? The last of those possibilities, elevated, is the ideal position for a truck to be in while parked on an even stretch of ground.
Though it might seem strange, trucks are actually designed to hike slightly toward the rear when parked and empty. This is to accommodate for the extra weight that trucks often carry when the back is loaded with heavy objects, such as boxes and furniture. If the truck were to sit flat when empty, the extra weight could cause the vehicle to sag low at the rear. Therefore, if the parked truck is flat when empty and back-slouched when full, it's possibly a sign of worn leaf springs.
Conducting the Inspection: How to Know When the Leaf Springs Are Worn
Leaf springs are subject to wear and tear over the course of several years, largely because of the various moving parts that comprise the springs. Leaf springs can also start to lag from prolonged periods of uneven weight distributions from within a vehicle. In any case, leaf springs should be checked at regular durations, which would be every 12,000 miles for most trucks. With certain trucks, there might be a shorter recommended interval, so it's always best to check with your auto manufacturer.
In advance of checking out the leaf springs under your truck, park it in a flat area and inspect the truck from a distance to see whether it sits straight or slouches in some way. For this inspection to be accurate, you'll need the gas tank full and the tires at a regular pressure. The non-passenger kerb weight of the truck should also be representative of the vehicle's normal state.
Put yourself at a reasonable distance from behind the truck and examine the way it sits on the ground. Does it appear level from left to right, or does one side slump to a slight degree? If there is a slump, it's likely due to a weak or damaged leaf spring on that side.
Funny though it may seem, a truck can actually start to sag on the left side when the driver is the sole occupant of the vehicle for extended periods of time. When the sag becomes visually obvious, it's a telltale sign that the leaf springs are due for a change out.
For the second part of the inspection, walk over to each side of the truck and study the nature of the swinging link spring shackles. The links could either be at the front or back of the springs, but in any case, they should lie flat if the truck is at kerb weight.
If one or both of the springs appears to be compromised, inspect the matter further for evidence of the cause. The problem could stem from undue impact on one or both of the leaf springs, or the issue could simply be due to the ravages of age. A broken leaf spring is something most truck drivers face at some point.
Why Leaf Springs Fail
The average leaf spring consists of anywhere from four to ten leaves of spring steel, each of which are cut at different lengths and bonded with clamps. When you see a leaf spring broken, the damage might consist of scrapes or cracks along one or more of the leaves within the spring.
One of the main causes of leaf spring damage is when leaves generate friction between one another as the truck makes suspension movements. Over time, broken leaf springs symptoms are often the result of such activity. Some vehicles, apply specialized leaves to circumvent this problem. However, even the tapered-profile single leaves of leaf springs eventually go bad or become compromised.
How to Clean a Leaf Spring
The most important reason to clean leaf springs on a periodic basis is because of the dirt particles that kick up from the ground as the truck is in motion. That dirt makes its way between the leaves, and this can exacerbate wear and corrosion on the leaf springs. The handbook for your truck should state the appropriate frequency for leaf spring cleaning.
One of the things you shouldn't do during leaf spring maintenance is treat the leaves with lubricating oil. If you do, it could hinder the anti-friction matter that lies between the leaves. If you do want to apply something of the lubricating sort, silicone-based lubricants are ideal.
On most of today's trucks, leaf springs are located at the rear suspension, so you'll need to slide under this area of your vehicle to access the leaves and perform the basic cleaning work. Depending on the height of your wheels, you may or may not need to jack the truck to perform these steps.
If you do need to jack your truck to reach the leaf springs, you'll need to:
- Take off the trims and hubcaps from the wheels.
- Loosen the wheel nuts.
- Activate the jack on either the left or right side of the truck.
- Place the axle stand under one of the chassis members - don't place the stand under the axle.
Repeat these steps on the side you didn't jack. Now, you should have both sides of the truck elevated with axle stands under the chassis. Place chocks ahead of the front wheels and take off the rear wheels. This way, the truck will be securely in place, and the weight of the vehicle will be significantly minimized around the springs.
Now, the leaf springs should be clearly visible and easy to access for maintenance. The hard work, however, is just getting started.
Now it's time to clean the leaves, which can be a rather tough undertaking if the dirt is caked on thick. Due to the old grease that will be on the leaves, the job can also get dirty, so you'll want to wear gloves, grubbies and goggles as you clean the springs. The work in question can also end up staining the ground as the dirty oil drips off the truck's underside, so you'll want to cover the pavement or garage floor with newspaper.
With a wire brush in hand, remove every bit of dirt you can see on each of the leaf springs. Try to be especially thorough along the leaf ends, the clips, the tops and the bottoms. By the time you're done with this step, the leaf springs should look more like they did when they were first installed, providing the leaves haven't incurred damage.
If greasy dirt is really caked on thick, you might need to use a degreasing fluid on the leaves. The best option here would be a spray fluid, which will help remove the gunk as you run the wire brush across the surfaces. Once the leaves are as dirt-free as possible, wipe the fluid residue off your wire brush with clean rags.
If the leaves don't appear greasy in the slightest and are only marked with dry dirt or corrosive streaks, don't bother with degreasing fluid. The wire brush should be enough to remove all the dirt. Even if the leaves have not been treated with grease, it's still up to you whether you want to introduce a silicone lubricant to the springs.
With the leaf springs now clean, it's time to get out from under the chassis and lower the truck back to the ground. Basically, you'll need to reverse all the jacking steps. Reattach the wheels, remove the axle stands, lower the jack and reapply the trims and hubcaps. Be sure the wheel nuts are tight, and everything is securely in place.
Inspect Leaf Springs and Mountings
During the process of cleaning leaf springs, you might spot evidence of damages to the leaves that may or may not be reversible. That's why important to know how to distinguish springs with minor wear from springs that would simply need to be replaced outright. Here’s what to look for:
- Check to see whether one of the leaf springs is more perfectly horizontal than the other. If there's indeed a disparity, the truck is likelier to sag on one side. In this case, it would also be pertinent to examine the ride height.
- Study the edges of the leaves. Do you notice any chips or cracks? Once leaves have incurred fractures, the problem cannot be rectified with welding tools. In fact, if you spot damage of that nature, that's how you know when to replace leaf springs.
- Examine the bottom sides of the leaves, where the stacking order goes from narrowest on up to widest like an inverted pyramid. The end tips of the bottom leaf might possibly poke at the underside of the wider leaf on top. This phenomenon is something to beware of, because it possibly means all but the narrowest of leaves have incurred a depression from the leaves directly below. This issue can be caused by the binding formation of leaf springs, where the leaf strips are squeezed tightly to one another.
You should be most concerned about the extent of depression. If the depression is only minor, you don't have to worry. However, if the depression surpasses 3mm, the problem is likely out of hand and won't be salvageable, not even with repair work.
- Look at the shape of the shackle pins that fasten the rubber bushings. Are they straight and stain-free, or have they lost their shape and gone rusty? In the latter case, it could be difficult to unfasten the pins. Therefore, the job of changing them out might be best for a professional.
Inspect the Condition of the U-Bolt
You’ll also want to check to see that the U-bolt nuts are fastened securely, as these are what bond each of the leaf springs to the axle. If the nuts aren't sufficiently tight, the position of the axle could end up compromised by the springs, and this could negatively impact the truck's steering power, braking mechanisms and tire quality. Tighten these nuts if it's necessary and possible, and change out any nuts that fail to secure the springs properly.
The bolts or pins that fasten each spring to its corresponding mounting pad must also be free of wear or damage, otherwise the axle might shake the leaf springs loose.
The leaves of each spring are attached to one another by U-shape clips at the outer side, which are in turn fastened with bolts or rivets. If either of these clips appear to be slipping from the springs or are in any way worn or fractured, they should be changed out for new ones as soon as possible.
When the clips are weak, the spring loading cannot do its proper job whenever the truck passes across shaky or treacherous ground. Consequently, the main leaves could snap as a result of undue stress at the point of full suspension travel.
On certain leaf springs, the narrowest leaf at the bottom will not be fastened to the other leaves by the spring clip, but will instead be held in place by the U-bolt. Consequently, if the U-bolt loosens, the bottom leaf might turn slightly outward. If this has happened to either of the leaf springs on your truck, lightly knock the bottom leaf back into alignment with a hammer and re-fasten the U-bolt.
Inspect the Rubber Bushings
To inspect the quality of the rubber bushings at the end of each leaf spring, you'll need to have the bushings wiped as clean as possible. Check each bushing for evidence of damage or wear, which would indicate prolonged stress from the truck's weight on suspension. It's also possible for the rubber to have cracked or spoiled over time through exposure to dirty oil.
If the rubber bushings do in fact need to be changed out for fresh ones, it’s best to leave the task to a professional. This is because of the process involved with the unfastening and fastening of bushings — a process that includes the application of hydraulic equipment. Though it might seem like a minor aspect of broken leaf spring repair, the quality of the bushings is actually quite critical to the overall performance of the springs.
Check for Corrosion and Unevenness
To check for sideways movement from the leaf springs, you'll need to have the axles relieved of the truck's weight. Take hold of one of the springs and see if it can be turned sideways, either way, to any degree. If the spring refuses to turn in either direction, it will have passed the test. Repeat this test with the other leaf spring.
At the heart of this very test is the rubber bushings, which should keep the springs from turning in any way. That is what makes the bushing one of the more critical parts to check when you fix sagging leaf springs on a truck. In fact, leaf spring repair could all boil down to the tightness and quality of the rubber bushings. If either of the leaf springs does turn, however slightly, toward one side or the other, have that spring's bushing changed out for a new one.
Inspect the shackle bolts to see how tightly each has been fastened. This can be done with either a ring spanner or socket. If any of the nuts or bolts are loose, tighten them up accordingly. This simple tightening of the shackle bolts is another step that can fix sagging leaf springs.
Inspect the floor pan, as well as the chassis member closest to the mounting, for evidence of rust. After all, rust can spread from one component under a truck to anything attached that's made of metal, and rust is one of the ultimate markings of bad leaf springs.
Lightly tap the parts of the underside nearest to the springs with a hammer to ensure the metal is sound. If corrosion has spread along the floor pan and mountings, the truck should be taken in for repairs. Suspend all regular use of your truck until the corrosion issue is fixed. Even though changing leaf springs is good for your truck, a rusting underside could quickly render that fresh pair of springs powerless.
If the rusting is minor and confined to merely a few metal surfaces along the rear underside, scrape away that rust with your metal brush. To prevent the rust from returning or spreading, treat the spots in question with a rust preventive, and top that off with a sealant formula.
Buy New Leaf Springs From General Spring
Broken leaf spring repair work is relatively easy to master once you've learned how to spot the problems on a particular spring. While it can depend somewhat on the type of problem at hand, dedicated truck owners can learn how to fix a broken leaf spring in almost any situation. Once a problem has been assessed, the crucial next step is to buy new leaf springs from a name you can trust.
Here at General Spring, we provide the parts that truck owners need for proper rear suspension on any terrain. Our inventory is stocked with a wide array of leaf springs and coil springs, as well as customized springs and individual parts for leaf spring sets. We check each product for quality before shipping, and all of our leaf springs are backed with a one-year warranty.
For more than 50 years, General Spring has been a suspension authority and a provider of leaf springs for all kinds of trucks. To learn more about our inventory, view our products pages. Have a question? We’re happy to help. Contact us today.