The springs on your vehicle are an integral part of its suspension system. Not only do springs keep all four corners suspended at a pre-determined, level ride height, they are designed to compress and recoil within safe limits - keeping your car or truck stable as suspension components travel up and down over an unstable world.
To suit a variety of customer preferences, springs can be built to produce a softer ride with more bounce, or they can be configured for a stiffer ride with less bounce. Regardless of the ride characteristics springs may be engineered with, they would continue to bounce up and down for an extended period if left unchecked. To dampen and stop this kind of excess spring motion that would make controlling a vehicle difficult, shock absorbers are fitted to work alongside the springs.
Springs typically last a long time and, in some cases, can even last the lifetime of the vehicle. However, that doesn't mean springs don't wear and become worn out over time. When springs do reach the end of their lifespan because they've lost their resilience or have become broken, ride quality and safety suffer.
As springs age and lose their ability to bounce back, they tend to sag. A spring that's weak doesn't carry its fair share of the overall load, and may cause unpredictable behavior during cornering, braking, or acceleration. Such a spring will become fully compressed more easily - causing "bottoming out" over bumps and putting other suspension components at risk for damage. Worn springs can also allow excessive body lean around turns - a factor that contributes to an overall loss of control. Depending on the type of spring, a gradual or noticeable increase in vibration and harshness may be felt in the vehicle's ride quality as well.
When it comes to different styles of springs, there are three main types made of metal that don't require electricity, hydraulics, or air pressure to function. Those types are: coil springs, leaf springs, and torsion bar springs.
In this article, we'll discuss how each of those springs are designed, and we'll tell you how to recognize signs that it's time to replace them. But first, we'd like to stress the importance of changing front or rear springs as a pair, and not singularly. Even if a front spring on just the driver side is broken, you should still replace both front springs to ensure they perform equally and predictably as a pair, and that ride height is level from side to side. That passenger side spring may appear okay, but odds are it's pretty worn and in need of replacement too. One new spring on the driver side would create a lop-sided imbalance.
Coil springs are wound in a spiral formation and are positioned vertically on the vehicle. Most modern passenger cars and many trucks built in recent decades feature coil springs at all four wheels. On "MacPherson strut" assemblies as well as coilovers, a shock absorber is fitted inside the center of the coil spring - and both are attached to the strut itself. On vehicles without struts, coil springs and shock absorbers are mounted separately.
As coil springs age, they are susceptible to the kind of sagging that causes a drop in ride height. This may show itself as a vehicle that droops low on one corner, or in the entire front or rear. When a moderate amount of weight is added to the vehicle (several passengers in the back seat, etc.), the vehicle will drop down a whole lot more than normal because of sagging or broken coil springs. In other cases, a worn spring can sit at the correct height when the vehicle is empty, but quickly sag under load because the ability to carry weight is lost.
When sagging springs put up less resistance, a vehicle's suspension is routinely allowed more travel than it's supposed to have. Dips in the road you never gave much thought to now cause the vehicle to "bottom out" because the suspension hits the bump stops. In a worst-case scenario, oil pans, transmission pans, and other low-lying mechanical components can suffer damage.
Because coil springs are often fitted to vehicles with more sophisticated independent, multi-link suspension systems, improper ride height has more of a negative effect on wheel alignment and tire wear. If you think your ride height may be sagging, vehicle manufacturers typically list ride height specifications in owner manuals and on the internet. It's easy to make a measurement yourself for comparison purposes.
Broken Coil Springs
Coil springs that have snapped due to corrosion will typically make groaning, popping, or other noises as weight shifts. If you suspect this is a concern, perform a close-up examination of the spring. If you can't see a visible break, carefully feel around all sections of the spring. Some coils are wrapped with a rubberized coating that can keep the spring loosely held together while concealing a break in the metal. When running your hand over the spring, such a break will feel much like a broken bone does to a doctor.
When any jagged edges of a broken spring stick out far enough to scrape the inner sidewall of the tire, a flat (or even a blowout) will occur in short order. Save yourself the cost of a new tire along with a whole lot of other grief, and have the vehicle towed if you see edges of the spring protruding into the tire area.
Strut Bearing Plates
Although this is a less frequent problem, a damaged or compromised upper bearing plate (on top of the strut, where it bolts to the vehicle) can cause a coil spring to bend and twist in a manner it's not designed to. This is often a reason why coil springs snap.
With the vehicle parked and running, have a helper turn the steering wheel fully from one side to another. While this is happening, listen closely to the area where the strut mount is bolted to the vehicle frame under the hood. Strut bearing plates can become bent or compromised by hard impacts such as potholes, and a bad one will produce a creaking or binding type of noise.
If you're replacing coil springs, it's also advisable to install new spring seats and insulators to ensure you've got a solid metal mounting base underneath along with new rubber cushioning pad.
Typically found on vehicles with solid axles such as pickups, SUVs, and vans, a leaf spring setup is composed of one or more lengths of arched steel pieces mounted horizontally between the axle beam assembly and vehicle frame. Multiple leaves are stacked on top of each other, and can be situated above or below the axle. Regardless of their actual mounting position, leaf springs support the weight of the vehicle while serving to secure the axle to the vehicle frame.
When leaf springs reach a certain wear point, the leaves can develop visible cracks and corrosion. Heavy loads or impacts may even cause a worn leaf to break apart, with a section of it falling off the vehicle entirely. As years progress, rubber bushings in spring eyes and shackles dry up and crumble, causing a noticeable increase in ride harshness.
Like coil springs, leaf springs are susceptible to sagging when they become weaker. If you feel like your vehicle's ride height is uneven or low all around, measure the vehicle's ride height and compare it against manufacturer's specifications. If you use your truck for hauling heavy items, bottoming out over bumps can be particularly harmful to other suspension components and even your payload.
Torsion Bar Springs
Torsion bar springs don't flatten out like a leaf spring or compress like a coil spring. Instead, a narrow steel tube attached to the vehicle's control arms twists along its axis, or length, when that control arm travels up and down. The other end, bolted to the frame of the vehicle, is fixed in place and does not twist. When a wheel strikes a bump and moves upward, tension is created as the bar twists out of shape. After the bump, the steel bar unwinds and pushes the wheel downward again.
Torsion bars are typically mounted horizontally in a front-to-rear position on the vehicle, and take up less overall room than coil or leaf springs do. Torsion bars of longer length also allow more up-and-down wheel travel, so they tend to get used on compact 4x4s. Attachment ends are usually either hex-shaped or splined, and mounted within an anchor piece known as a "key".
The position of these keys can be adjusted with a wrench to vary a vehicle's overall ride height. As the key is turned to the raised position, the ride height of the vehicle increases - or vice versa. Spring rates of torsion bars are determined by a bar's overall diameter, length, and material composition (usually steel alloy).
While some automakers like torsion bars because they're less expensive to produce, the main appeal is their compact dimensions which allow more room for drive axles and other suspension components in tight spaces. And because ride height can be adjusted, it allows a vehicle owner to set things to their own preference.
Sagging ride height is the most common indicator of worn torsion bar springs, along with a harsher ride because the bars have lost some of their range of twist. While the position of the torsion bar key can be changed to allow some correction of sagging ride height and correct potential alignment issues, it will not restore spring resilience that has been lost over time.
If you're hearing metal-on-metal noise, a common cause of it is rubber cross member mounts that have dried up and crumbled away. We'd also recommend checking the torsion bars for any visible cracks, because the bar will eventually break apart sooner or later.
Because you won't be able to visually inspect all sides of the bars, run your hands over the length of them. Cracks may or may not be large enough to detect with your fingers, but any rust patches will feel rough to the touch. If you detect either of these conditions, the torsion bar is compromised and needs to be replaced. Note that if bolts which anchor the ends of the torsion bars in place are rusty, then the rust has spread to the torsion bar itself in the area around the bolt holes.
Opportune Times To Replace Springs
Replacing springs is usually a straightforward job, keeping in mind that components can be heavy, and that chassis components, being exposed to the elements, are more likely to suffer from corrosion. For safety's sake, spring replacement should never be attempted unless the weight of the vehicle is off the ground with 2 or 4 wheels properly supported by a lift or jack stands. In general, the higher the vehicle, the better the access.
With coil springs mounted individually or as part of a McPherson strut, a spring compressor tool will be needed to squeeze the springs down before they can be safely removed. This is a major safety concern: uncontrolled release of a coil spring under tension can cause severe personal injury.
There are a few related repairs that require removal of springs (or struts) in order to perform. During these repairs, there's no extra labor to install new springs - only the cost of the parts. Probably the most common repair is the replacement of a strut assembly. Today, many struts are sold complete, with new coil springs mounted in place. If you're in the process of replacing worn shocks on a strut-equipped car, be sure to consider the whole assembly if you need springs too, as you'll get both.
Another such common repair includes replacing damaged control arms and/or worn control arm bushings. Depending on suspension design, installing new shock absorbers may require springs to come off - but not always. If you've got leaf springs, replacement of damaged or worn shackles is an opportune time to pop a new set of springs on.
Naturally, any serious repairs which require removal of the entire suspension are also an opportune time. This includes, but is not limited to, replacement of an engine subframe, dropping an engine out of a vehicle from below, and removal of solid front/or rear axles.
Now that you know what to look for, you'll no longer have to guess whether it's time to replace your springs or not. When the need for replacement does arrive, we'll help you take the worry out of finding the right products - thanks to our full line of OEM style springs that match the size, thickness, shape, and overall function of your factory ones - restoring the ride quality your vehicle was created to have. We have more detail about the workings of vehicular springs in our related article which you can find here.
We've also got a full range of performance suspension components such as coil springs, leaf springs, torsion bars, air suspension kits, shocks & struts, and more that let you customize your stance any way you like! We're glad to help with any product questions you have regarding these items and any others, just give us a call seven days a week.