Leaf Springs vs Coil SpringsLast Updated August 8, 2023 | Alison Smith
Leaf springs and coil springs play an important role in a vehicle’s suspension system. Both types of springs help improve steering stability, ride comfort, handling, and traction.
Most modern-day cars use coil springs while leaf springs are common in older vehicles. Although coil and leaf springs serve a similar function, there are advantages and disadvantages to each.
What Are Leaf Springs?
Leaf springs are a common component of older suspension systems. They consist of metal sheets in various sizes stacked on top of each other. Leaf springs were predominantly used before the late 1970s. You can find them in many vehicles, from horse-drawn carriages to the Model T.
Since leaf springs spread the weight of a vehicle over a wider area, they’re used on larger vehicles like trucks, vans, and heavy-duty pickups today.
How Do Leaf Springs Work?
Leaf springs flatten as they encounter force, which helps dampen the bumps and jolts of the road. The metal leaves are perpendicular and curved toward the road. They flex under pressure and can handle very heavy loads.
Leaf springs are connected to the vehicle by leaf spring shackles. These free-hanging loops allow the leaf springs to change in length to adjust to different road conditions.
Leaf Spring Suspension Pros and Cons
Despite the shift toward coil springs, there are still many advantages to using leaf springs. Their simplicity, strength, and reliability make them great for off-road and commercial applications. They aren’t without their disadvantages, though.
Leaf Spring Pros
In a leaf-spring suspension setup, the spring supports the axle. This simple design makes them easy to install, upgrade, and repair. You can replace individual leaves or adjust the flexibility by adding or removing leaves.
It’s easier to modify leaf springs to enhance performance, increase ride height, or improve tire stability and handling. Coil springs have a much more complex suspension setup compared to leaf springs.
Along with their simple design, leaf springs are a reliable form of suspension. It’s one of the reasons they were commonly used in vehicles before coil springs became popular. Leaf springs were low cost but dependable.
The strength and heavier weight of leaf springs add to their reliability. Higher unsprung weight in a vehicle can increase the wheel’s contact with the ground. This means better traction in muddy or slippery situations.
Superior Hauling Power
Leaf springs have a tight structure that allows them to distribute weight across a wider area. As such, they can handle heavier vertical loads compared to coil springs. They can also support the weight of heavier vehicles. Many commercial vehicles come equipped with leaf springs because of their hauling power.
Leaf Spring Cons
Reduced Approach and Departure Angles
Leaf springs don’t allow for the same approach and departure angles as coil spring suspensions. Because of the way they fit under the frame of the vehicle, they can impede wheel travel when on too steep an incline or decline.
Leaf spring shackles also affect these angles. Altering the shackle length will add some height. But this also affects the caster angles, which can negatively impact the approach and departure angles. This is primarily an issue for off-roaders.
Prone to Axle Wrap
One potential issue of using a leaf spring setup is axle wrap. Axle wrap is when the rear axle housing twists when heavily accelerating. This can not only break the leaf springs, but it can also cause the driveshaft to come loose. The transmission could also break in the process.
Another potential issue for leaf springs is shackle inversion. This is when the leaf spring shackle moves past its designated axis of movement and gets stuck.
Shackle inversion is a common problem encountered when off-roading. When this happens, the entire suspension system is inoperable and can cause further damage to the vehicle if you continue to drive.
Both axle wrap and shackle inversion don't occur with coil spring suspension systems.
What Are Coil Springs?
Most modern-day vehicles use coil springs in their suspension setups. The coils themselves are basically giant springs that are wrapped around shocks or struts. Coil spring systems work with a variety of control arms, shock absorbers, and linkages to provide suspension for each wheel.
How Do Coil Springs Work?
In most coil spring suspensions, a central coil provides the bulk of the dampening force. A series of arms from the suspension connects to the wheel and keeps the wheel attached to the vehicle, allowing it to flex. Because each wheel can adjust to the road conditions individually, this greatly improves ride quality.
Coil Spring Suspension Pros and Cons
There are several benefits to a coil spring suspension, including greater flexibility and comfort. Considering the robustness of coil springs, there aren’t many problems with this form of suspension. That being said, they can be more expensive and aren’t suitable for very heavy vehicles.
Coil Spring Pros
Greater Flexibility and Comfort
Although coil springs are like a rigid slinky, they’re more flexible than leaf springs. The greater flexibility offers a wider range of suspension movement. The coil spring’s ability to bend and flex is what helps absorb bumps and potholes in the road. The stiffer the spring, the rougher the ride.
Each individual piece of a coil spring suspension system can be changed, altered, and upgraded. Many off-roaders opt for coil spring systems so they can customize and fine-tune them to their desired specifications. You can customize your spring's function and stiffness by choosing between linear, progressive, or dual rate springs. Stiffer springs and tougher sway bars are better for off-road applications.
There are also many modifications you can make to coil spring systems for performance reasons. For example, you can install panhard bars on your Mustang if you want to limit axle movement. Because coil springs have a wider range of motion, they allow for finer tuning compared to leaf springs.This makes them the optimal choice for performance vehicles.
Performance and Off-Road Capability
When it comes to off-roading, coil springs allow for the most articulation. Whenever you see images of Jeeps that look like they’re in the middle of a contortionist act, that’s a coil spring suspension system in action. Along with unparalleled articulation, coil springs offer the best approach and departure angles. With a well-tuned coil spring suspension system, your vehicle can conquer seemingly impossible rocks.
Coil springs also improve handling when it comes to performance driving. During cornering or sharp turns, the springs will compress. This will increase the firmness of the suspension to control bumps and body roll. Yet they maintain a soft, comfortable ride when cruising down straightaways.
Coil Spring Cons
Can Be Expensive
Coil springs are more expensive than leaf springs. The individual parts are no more expensive than leaf springs, but there are significantly more parts in a coil spring setup.
Additionally, the delicate alignment needed for coil-sprung suspensions can prove to be a difficult job to do at home and could end up requiring professional installation.
It’s also more expensive to convert a leaf-spring suspension system to a coil-spring setup. Retro-fits can get pretty expensive and require a lot of work.
Not for Heavy Vehicles
Because they aren’t as stable as leaf springs, coil springs aren’t as good for heavy vehicles. Coil springs are lighter than leaf springs and the concentration of vehicle weight can put a strain on the springs. This can cause the coils to break or crack, especially if corrosion is present. That’s why many medium- and heavy-duty trucks and commercial vehicles still use leaf springs. A coil spring suspension system can also go bad over time, so if you notice any symptoms of bad shocks or struts, it may be time to replace them.
Are Coil Springs Better Than Leaf Springs?
Whether coil springs are better than leaf springs will depend on the type of driving you engage in most. Both suspension systems are suitable for most driving applications.
Leaf springs are better for heavier vehicles and those who may need to haul more weight. They’re also simpler but less adjustable than coil springs.
Coil spring suspension systems are better for performance driving as you can fine-tune your suspension. They offer greater comfort and flexibility for improved handling.
There’s a reason coil springs have replaced leaf springs in modern suspension systems. But leaf springs still have their place in the auto industry today.