(Updated on June 9, 2021)
Coil springs are the major component of modern suspension systems that keep your vehicle “suspended” off the ground. These springs absorb impact from bumps in the road by compressing and expanding.
How Do Coil Spring Suspensions Work?
The compression and rebound of the coil spring, coupled with the damping applied by the shock absorbers, work to keep each tire in contact with the road at all times. Coil springs are also a key factor in determining the ride height of your vehicle.
There are four coil springs to support the weight of your entire vehicle, which means each of these springs must be incredibly strong. Each spring is designed from the factory with a specific spring rate that maximizes comfort and performance for your particular vehicle.
Springs and shocks are the two main components that determine how your vehicle reacts to bumps. Some shocks are mounted inside the coil spring. This is called a coil-over shock absorber suspension setup, or “coilover” for short.
Many vehicles come with coilover suspension from the factory, but there are a plethora of aftermarket options available that allow you to lower your ride height or alter spring rates for better cornering performance.
The upper part of the coil spring is positioned below the spring perch (sometimes called a top hat in coilover suspensions) while the bottom part of the spring is positioned on the lower control arm. As you may know, the lower control arm assists in keeping the wheels securely held in place.
Since the spring is above the lower control arm, it absorbs all the shock from down below. That way, the people inside the cabin above the coil spring can remain comfortable as they drive over obstacles on the road.
Top 5 Bad Coil Spring Symptoms
If you have a bad coil spring in your car, there are definitely going to be some noticeable symptoms that you will experience. Once you recognize them for what they are, you should do something about them immediately.
Below are five of the most common signs you have a faulty coil spring.
1) Sagging Corner
If you have a bad coil spring, that corner of the vehicle might sag more or appear lower than the other corners. This will easily be noticeable simply by looking at it from the outside.
But when you are driving the vehicle, you will have less stability from this sagging too. This problem will cause other symptoms to get worse, such as excessive tire wear and tear.
Coil springs are supposed to keep the vehicle from shaking and bouncing up and down as it goes down the road. But if you have bad coil springs in your vehicle, then they won’t be able to prevent this bounciness.
This means that you will experience a lot of bouncing and shaking as you drive, especially if you travel over rough terrain or roads with many potholes. This will likely make the vehicle very difficult to control.
Note that a bad shock may exhibit similar symptoms. Typically bad shocks are unable to absorb the rebound of the spring, so your car feels more like a trampoline when you hit a big bump.
See Also: 10 Best Shock Absorber Brands
3) Uneven Wear on Tires
Coil springs are supposed to keep the wheels and tires in contact with the road at all times. This allows the tires to receive an equal amount of wear and tear as they’re moving on the road.
If you have bad coil springs, your tires may even leave the road at times, just under regular driving conditions. Once that happens, the tire treads will wear prematurely and unevenly causing drivability issues on the road. You will also need to replace tires much quicker than normal even if tire rotation is done.
4) Rattling or Clunking
In addition to the shaking that you will experience from bad coil springs, there will be an annoying clunking or rattling noise coming from the suspension system too. This rattling noise will increase in volume as you accelerate the vehicle more and drive over rough roads.
Do not just ignore this rattling noise because it is an early warning sign that you need to get your coil spring replaced.
5) Warning Light
Most newer vehicles have warning lights for the traction control system of the vehicle. There are sensors built into the suspension which keep track of the vehicle’s stability.
Whenever the sensors detect any unusual behavior, it will cause the warning light to illuminate on the dashboard. Take this as a warning sign that there’s a problem with your suspension, possibly your coil springs.
You might not realize the exact problem at the time, but you will know soon enough if you experience the other symptoms too.
How Long Do Coil Springs Last?
Since coil springs are thick, round pieces of steel, they typically last the entire life of the vehicle. The main exception to the rule is on cars with significant corrosion.
You may experience high levels of corrosion on your vehicle if you live in the Salt Belt in the United States, for instance. If your roads are salted, expect the life of all external components to be drastically reduced. One way to mitigate this is with frequent undercarriage washing during the winter months when roads are salted.
If your vehicle’s suspension system has been modified by either cutting the springs or using spring clamps, the life of the coil spring may be reduced. Spring clamps put constant, uneven compression on the coil spring in a way it was not designed for.
Coil Spring Replacement Cost
Coil springs are inexpensive parts that typically cost around $100-200 for the part alone. Labor cost ranges from $100-400, depending on the vehicle. Sometimes you can buy a pre-assembled coilover, which substantially cuts down on installation time.
Since it’s generally recommended to replace suspension components in pairs (left and right), the total cost will likely be higher if you are replacing components on both sides of the vehicle.
Can I Replace Coil Springs Myself?
While it is possible to replace coil springs yourself, you should really know what you’re getting into; this is a job that’s often best left to the professionals. Make sure you do plenty of research on your specific vehicle before you decide if attempting this job is right for you.
Even when your vehicle is lifted off the ground, coil springs are under a tremendous amount of force, which means they have a dangerous amount of potential energy stored. The larger your vehicle, the stronger the springs have to be. Many springs can only be replaced by using a spring compressor.
Use extreme caution when using a spring compressor, as misuse could cause serious injury or even death. Only compress the spring as much as is necessary, and wear gloves and eye protection at a minimum.