Learn how car leaf springs work and why they are essential for a smooth ride. Discover maintenance tips to keep your car leaf springs in top condition.The evolution of the bow and arrow took the form of the crossbow, a weapon that we know has existed since 4 or 5 centuries before Christ, as Sun Tzu mentions it in the iconic book The Art of War . It is often said that good design is completely timeless, and it is interesting to know that the same operating principle of this weapon is also used in the automotive world.
How Does Car Leaf Springs Work
No matter how much technology advances, there are systems that are still used because they are simple, effective and cheap to implement. Just as we have cars with brakes that follow the same principle perfected by Bertha Benz in 1886, the leaf spring suspension is another mechanism that was used in cars even before they started to have combustion engines.
What is a leaf spring suspension?
Imagine a truck, an all-terrain vehicle, a city utility vehicle, and a sports car. They are all vehicles with a chassis, a body, and, most likely, four wheels. However, they are not all created equal or made with the same components. For a vehicle to function properly, the right components must be used .
One of the main challenges facing automotive engineers is the suspension of the vehicle’s mass . This is a critical point, as it determines the vehicle’s handling, comfort and the weight that can be supported. Although the leaf spring suspension is one of the oldest known , it is still used in some modern vehicles because it is cheap to implement and gives good results when supporting heavy loads or tackling difficult terrain.
The spring suspension consists of several superimposed steel plates , known as leaves, which flex to absorb the irregularities of the terrain. Its operation is exactly the same as the weapon, taking advantage of the elastic flexing of the material to recoil and then recover its original shape when the resistance disappears.
What are the advantages of leaf spring suspension?
Leaf springs are usually used only in cargo and off-road vehicles . It is not a perfect system, but it does have some important advantages over other more complex or expensive systems:
- Load capacity : the arch of the leaf springs allows the weight of the vehicle to be distributed along the entire structure, reducing stress on specific points of the chassis. Thanks to this, a lot of weight can be carried without the vehicle suffering any damage.
- Durability and low maintenance : The robustness of crossbows makes them ideal for harsh environments. Their simple design means fewer moving parts, which translates into less wear and tear and less need for regular maintenance.
- Simplicity : Of all the suspensions that exist, the crossbow is one of the few that even a child could understand, due to how extremely simple they are.
- Stability and Versatility : Leaf springs offer consistent performance on a variety of surfaces, from paved roads to rough dirt trails.
What vehicles use leaf spring suspension?
The origin of the crossbow is in catapults, which are speculated to have been used for the first time in ancient Egypt. Centuries later, in 1804, the British inventor Obadiah Elliot discovered that he could use this same system to support the loads of carts and carriages, laying the foundations that are still used today, a couple of centuries later, in vehicles such as those listed below:
- Cargo trucks : from light trucks to heavy transport vehicles.
- Buses : especially models designed to operate on difficult terrain.
- Simple off-road vehicles : The most advanced and expensive off-road vehicles often use very expensive and complex suspensions. However, cheaper models such as the classic Suzuki Samurai do use this system, as it is robust and very cheap to implement.
- Some sports cars : Although not commonly used, the Chevrolet Corvette uses a unique transverse leaf spring configuration.
- Racing trucks : the trucks that take part in the Dakar also have this system, and it is obvious, because few suspensions are going to withstand conditions as extreme as those found in that rally category.
Types of leaf spring suspensions
There is no single type of leaf spring. Depending on the needs of the vehicle, this system has been adapted to perform one type of work or another. The most commonly used systems are the following:
- Elliptical leaf spring : This is the most common type. They support a lot of weight and are very resistant. They are called this because they have a leaf that curves in an elliptical way, connecting the ends to each axle and with the body in between.
- Semi-elliptical leaf spring : made up of two leaves joined together. They are lighter and easier to install, but cannot support as much weight.
- Transverse leaf spring : installed transversely to the vehicle, from one side of the chassis to the other.
What parts make up a leaf spring suspension?
If we analyze a leaf spring suspension, we will see that they are composed of the following elements :
- Master leaf spring : This is the main and longest leaf spring in the suspension. It connects directly to the vehicle’s frame, providing the primary support and structural connection for the suspension system.
- Load-bearing leaf springs – These are the additional leaves located below the main leaf spring. They provide additional reinforcement and increase the load-bearing capacity of the system. They flex together with the main leaf spring to absorb forces generated by uneven terrain or weight.
- Cap screw : This is the central screw that joins all the suspension leaves together. It keeps all the leaves aligned and compact, allowing them to work together as a single structural unit.
- Fixing eyes : These are the anchoring points of the main spring to the chassis of the vehicle. There are two types. The fixed eye is fully connected to the chassis, while the ‘ mobile twin ‘ attachment allows some movement to accommodate the bending of the spring during operation.
- U-bolts : U-bolts are ‘U’ shaped clamps that secure the vehicle’s axle to the leaf spring. They ensure that the axle is firmly attached to the suspension, allowing forces and loads to be efficiently transmitted between the chassis and the ground.
Leaf spring vs. spring suspension. What are the differences?
Although leaf springs are extremely simple and easy to maintain, passenger cars generally use spring suspensions , as well as other even more complex systems when it comes to high-end cars.
Despite the advantages of leaf springs we have mentioned, driving a vehicle with such a suspension is quite stiff and uncomfortable . For this reason, a large part of the passenger car fleet uses springs, i.e. a suspension that uses the physical principles of springs to absorb the irregularities of the terrain.
Springs compress and expand when the vehicle passes over an obstacle, dissipating the energy through the elastic deformation of the metal . This system is complemented by shock absorbers, which control the movement of the springs and prevent excessive rebound. On the other hand, the arms maintain the alignment of the wheels and allow the suspension to act in a controlled manner.
This system provides a smoother ride with less bouncing. On the downside, the components are more expensive to manufacture . In addition, this type of suspension can be damaged with use, and it is not as durable as a leaf spring.
We have finished with this topic, but if you want to continue reading about suspensions, in this other article we talk about the damage that speed bumps can do to your car, a very related topic. Another very educational article that may be useful to you is how to identify car faults from noises.