There are a lot of heated debates out there when it comes to comparing the performance of off-road suspension setups. However, I don’t think many are quite as heated as the argument over whether an independent suspension will outperform a solid axle suspension.
In the long run—with budget and time aside—the independent has more potential than a solid axle. However, very few of us have the luxury of making modifications without factoring in these restraints. And in that case, a solid axle suspension can be built to perform better than an independent suspension, dollar for dollar. Both have their benefits and it’s worth taking a deeper look to give a fair comparison.
Let’s see what all the forum fuss is about.
First Things First
Before we can discuss what’s better in terms of performance, we need to understand what the demands are. Among different build types, the features of each system will vary in terms of dimensions, but some key characteristics will always remain. When it comes to an off-road vehicle, the suspension must provide additional ground clearance, be versatile in performing on a variety of terrains through a variety of driving styles, and it will need to articulate well over that terrain.
Suspension articulation is incredibly important for off roading. To overcome obstacles, traction is needed at all times. As entertaining as it is to see one wheel come off the ground when someone is crawling, it can be detrimental (not to mention dangerous), as traction is completely lost—at that point, the suspension has hit its limit of articulation. A lot of builders modify their trucks or Jeeps to help increase the amount of travel their vehicle has. And if you were to refer to many of the online forums, you’d find a good amount of people arguing that the solid axle is the best platform for increasing flex.
Solid axle suspension systems are often found on older model vehicles—the common source pool for budget off-road builds. It wasn’t until the ’90s that full-sized pickups began using independent suspension from the factory. And even then, it was usually only in the front of the platform. (Solid axles were still used in the rear.) In fact, even off-road intended vehicles, such as JK Wranglers, still use solid axles.
So with all this preference for solid axle suspension setups, how is it that independent suspension is often considered, in concept at least, to be the superior design? Well, let’s break down the technical genetics.
What’s the Difference Between Independent Suspension and Solid Axle Suspension?
Solid Axle Suspension
The heart of any off-road suspension setup on a 4WD vehicle is the axle, in the sense that any suspension system must accommodate that axle’s design. For solid axle designs (sometimes also called “live axle” or “beam axle”), there are a variety of suspension types used. But in any case, both wheels will be connected to a single axle housing that runs the span of the vehicle. This solid axle that is physically connecting both wheels to the same housing, is what makes the suspension dependent. This means that regardless of the exact suspension type, one wheel moving up or down will directly impact the wheel on the other side.
“A solid axle setup can improve traction over big bumps and hills as well as gain more torque from the differential as there are fewer parts that power must transfer through,” says aftermarket manufacturer Fab Fours in a comparison between both systems. “Solid axles are also more durable than most independent front suspension (IFS) axles and can be easily changed in comparison, making axle repairs on off-road trucks no problem.”
When discussing independent suspension, often the term “wishbone suspension” will come up because of the design of the upper and lower control arms. The type of axle used in this sort of suspension is known as—you guessed it—an independent axle. At the center of an independent axle assembly is an axle housing in which the ring gear and carrier live. Instead of axle tubes running out to the wheels, CV axles are used. CV stands for “constant velocity” and refers to the transmittance of engine power at a constant rotational speed, regardless of turning angle.
This setup allows the wheels to move up and down without affecting one another. Again, we will find that there are a variety of suspension types used, but the fact of matter is that the wheels being able to move independently from one another comes back to the axle design.
According to Fab Fours, “IFS is more agile and maneuverable … by offering improved handling most of the time and freer movement of the individual front wheels and tires. It can provide more front end clearance in some instances, as the front wheels have greater articulation. Overall, it seems to be a more preferred and comfortable option for off-roading, especially when driving your outfitted truck or Jeep at higher speeds.”
Great in Theory, Not Always in Practice
The fact that solid axle suspension keeps the wheels from moving independently of one another while an independent suspension doesn’t, would give the initial impression that the independent suspension is superior. But there are some drawbacks. As mentioned earlier, it’s true that, dollar-for-dollar, you can get more out of a solid axle in off-road suspension setups. Of course, cost will vary. But, in general, to build up a solid axle extensively will run around $7,000-$10,000 while building an independent suspension system may run north of $15,000. Of course, these are figures based on extreme scenarios, but it still puts things into perspective.
In stock form, while the wheels can move freely of one another, travel is usually a bit less with independent suspension. Also, the setup isn’t as strong as a solid axle system, since it lacks a rigid beam interconnecting the two wheels. When the physical limitations of the design are paired with the higher cost of parts, it becomes apparent that the solid axle suspension is going to be the go-to choice for many off-roaders.
I always like to take the stance that the best performing system for your car or truck is the one that you can afford—which is usually what the vehicle comes stock with. However, in a fair argument, a well-built independent suspension system is going to outperform a solid axle system.
Allowing your wheels to move independently of one another means that the wheels can be on different surfaces, without having the issue of directly affecting one another. This means that traction will always be maintained.
Now, to many, the concept of having solid axles all around is the way to go. Even having independent suspension in the front is a no-go for some. But when you see the two in action, you will see that when comparing independent front suspension to solid axle front suspension, the independent suspension has a bit less trouble getting around obstacles. Check out the video posted below. In this clip, watch how the front wheel of the solid axle truck comes off the ground at multiple points, while the truck with IFS stays planted to the ground at the same points on the course.
Obviously, applying these capabilities to both ends of the vehicle would be ideal. But many off-roaders fear that the CV axles used in an independent suspension design won’t last. I say, look at the Gomez Brothers—off-road racers known for dominating King of the Hammers. Back in 2017, they went all out with their Ultra4 vehicle that has independent suspension all around. In 2018 they took 5th place in the King of the Hammers challenge, proving that with enough time and effort (and cash), these designs have some serious potential.
Money, Money, Money
So, what does this all mean for the Everyman? Well, ultimately, both have their share of advantages and disadvantages. In concept, independent suspension all-around will make for a vehicle that can overcome multiple surface types with ease, as the articulation of the suspension is independently handled wheel-to-wheel.
However, at this point in time at least, the amount of time and money that goes into making an independent suspension handle the challenges and travel as well as a solid axle set up makes the upgrade something of a pipe dream for many. So, when it comes down to it, an independent suspension will handle better than a solid axle, making it an ideal setup for higher speeds and smaller obstacles. But a solid axle’s traction on those big bumps and hills makes it the king of crawling.
Although, when it comes to budget, whatever is under your truck is what you’ll enjoy the most.