Unraveling the different suspension types available to better determine what your ride needs.
Few other components influence your driving experience and the overall performance of your vehicle as much as the suspension does.
In simple terms, its primary role is to maintain vehicle stability by absorbing energy from the wheels. However, the intricacies of suspension systems extend far beyond this basic principle, as evidenced by the sheer array of designs tailored for different purposes across different vehicles.
This suspension design is important, as it directly impacts everything from on-road driving comfort, acceleration, and handling, to off-road capabilities, payload capacity, and much more. This is why you'll find suspension systems that appear to be worlds apart beneath a 4x4, economy-level commuter, and a high-performance track vehicle, despite them all sharing the same basic function.
We're here to shed some light on the different suspension types commonly found in passenger vehicles so you can determine what to look for in your next vehicle purchase or how to make the most out of what's currently in your driveway.
Solid Axle vs Independent Suspension
Understanding suspension types begins with knowing the two primary types of axle setups found in vehicles, as the suspension system is designed around these configurations.
Both cars and trucks may feature either a solid axle or a differential with constant velocity (CV) axles connecting it to the drive wheels. The latter is more common, as CV axles allow the wheels to articulate independently from one another, which is what makes independent suspension systems possible. Vehicles equipped with independent suspension typically offer superior ride quality, performance, and handling compared to those with solid axle setups.
Solid axles get their name from the fact that the axle shafts are one continuous piece within a rigid housing. This isn't as popular of a design as it once was, but it's not inherently inferior to independent suspension. While handling and ride quality may suffer, solid axle setups offer durability, simplicity, and even some off-road benefits.
Types of Suspension Systems
Now that you understand the types of axles found in vehicles, let's get into the various suspension systems available. Below is a brief overview of the most common suspension types found in passenger vehicles.
It's important to note that these descriptions provide a simplified starting point. Delving into the nuances and providing in-depth explanations of each suspension type simply isn't possible in a single blog post.
Instead, these overviews aim to provide a basic understanding of the layout and the pros and cons of each style. Once you identify the suspension type in your vehicle (or determine the best option for your needs), further research is highly recommended for a complete understanding.
MacPherson Struts
The Macpherson strut system is most commonly found on the front end of front-wheel-drive economy applications. What distinguishes this suspension system is the multi-functional nature of the strut. In addition to its primary role of absorbing shocks and dampening vibrations, the strut also serves to “locate” the wheel assembly, or position and stabilize it.
The benefits of this design start with its simplicity. By cutting down the number of parts making up the system, the cost of production and maintenance are greatly reduced. This design also has packaging benefits that make jobs like servicing CV axles much easier.
However, there are drawbacks on the manufacturing side of the MacPherson strut system. The most notable concern for you will likely be its handling limitations. Fewer parts in the system limit its ability to remain stable under heavy body roll. Furthermore, it places more stress directly on the body, which can lead to larger maintenance issues in the long run.
Like maintenance, upgrades for this system are highly economical. While it may not be something you can modify for maximum performance, aftermarket strut assemblies can certainly alter performance and ride quality enough to make your car more enjoyable.
Double Wishbone
Double wishbone suspension systems offer performance capabilities beyond what the MacPherson strut can achieve. Found on both driven and non-driven wheels, the double wishbone utilizes both an upper and lower control arm shaped similarly to a wishbone – hence the name. Alternatively, these are known as A-arms.
The benefits of the double-wishbone setup hinge on improved articulation. This makes for a much more stable ride under severe body roll. The result is a car with superior performance and handling abilities and, of course, better ride quality.
The drawback of the double-wishbone setup is its increased complexity. This directly impacts both the cost and ease of maintenance, as it's harder to get an axle shaft in and out of the system – and you now have an upper control arm assembly to care for.
As far as upgrades go, there's a lot you can do to bolster the system. On top of changing shocks, struts, or coil springs, you can also move to aftermarket upper and lower control arms to improve performance and geometry.
Multi-Link (Independent)
A multi-link suspension encompasses a multitude of designs with varying complexity that can be found at both the front or rear of a vehicle. As such, it helps to think of them as an upgraded double-wishbone system, where individual control links replace the upper and lower arms to form the assembly.
The benefits of a multi-link system are compactness, reduced weight, and increased adjustability. This allows manufacturers to finely tune the dynamics of the suspension assembly to meet specific performance criteria for different applications. The drawback, however, is that breaking up the system into multiple parts adds complexity and difficulty to routine maintenance.
Upgrading this type of system can add extensive adjustability to the right application, particularly those with control links in place of both upper and lower control arms. Adjustable aftermarket links combined with adjustable shocks give builders the means to fully customize the ride quality and performance characteristics of their suspension.
Torsion Beam
Torsion beam or twist beam suspension systems are typically found at the rear of economy cars. This setup uses one large member that spans from side to side on the vehicle, supporting both wheels. This singular member serves to control lateral movements and is engineered to twist like a torsion bar to control body roll, hence the name.
The benefits of the torsion beam suspension are its reliability and simplicity of maintenance. However, it falls short in terms of handling and ride quality compared to its counterparts. There's little one can do to improve those qualities outside of installing aftermarket shocks and springs.
Trailing Arm
Trailing arm suspension systems are another option typically found at a vehicle’s rear, and can be used with any combination of axle and drive-type assemblies. They are characterized by the use of a pivoting trailing arm to control the lateral motion of the rear wheels. Depending on the drive type, either a solid axle or spindle and control arm are used to keep the wheel in place.
Since they are most commonly used in place of torsion beam type suspensions, improved handling and performance at the cost of ease of maintenance are the most notable gains. On a solid axle application, they are a niche product generally used in place of leaf springs to aid in launching and tracking performance on high-performance applications.
Axle on Leaf (Solid Axle)
Axle on leaf systems are primarily found on the rear of modern trucks with a solid axle. Historically, they could be found on both the front and rear of trucks, and even in the rear of some high-performance cars.
This system is incredibly reliable thanks to its ultra-simple and robust design. Locating the axle with just the shocks and leaf springs makes maintenance cheaper and easier than most other systems. It's also capable of supporting high-weight capacities, making it a clear fit for heavy-duty work trucks.
The drawbacks are all founded on limited articulation. Handling and ride quality are far inferior to what is possible with other systems. That said, axle on leaf systems can be altered in a few ways.
Leaf spring assemblies can be swapped out for stiffer or lighter packs to bolster performance and load capacity, and paired with leaf packs or shackles and blocks to alter ride height. They can also be outfitted with progressive springs to bolster weight capacity without harming ride quality. Of course, aftermarket shocks can also be added to influence ride quality and performance.
Similar to multi-link systems used for independent suspension, multi-link setups for solid axles replace a simple point of contact with multiple links to locate the axle. The number of links is typically indicated in the name, such as a 4-link setup.
These systems are commonly found on vehicles equipped with solid axles, where the multi-links serve as replacements for traditional leaf springs, representing an advancement in suspension design. Instead of using leaf springs to perform regular spring duties and keep the axle straight as the suspension moves, multi-link setups distribute these tasks among the links, coil springs, and shocks.
Advantages of a multi-link solid axle system include dramatically improved handling and performance, both on and off-road. However, they are far more expensive and complex than traditional leaf springs. Additionally, these systems may have lower payload capacity, which is important to consider for vehicles with both work and off-road duties.
Aftermarket multi-link systems are available for builders looking to customize their trucks or classic cars. Many conversion kits are even available for builders who want to get away from traditional leaf springs in favor of something a little more modern.