An Old Suspension Debate
The independent front suspension (IFS) is on a tear. It wasn’t that long ago (2001) that the entire Jeep vehicle line (Wrangler TJ, Cherokee XJ, and Grand Cherokee WJ) sported a solid front axle. Now, 12 years later, only one Jeep (Wrangler JK) has a solid front axle. IFS is also found under all new ½-ton and compact pickup trucks, all SUVs (excluding the Wrangler), and one-third of ¾- and 1-ton pickups sold in the U.S. Further, IFS is used on some desert racing trucks as well as Tough Trucks, King of the Hammers machines, and military vehicles. Does this trend mean that IFS is superior? Editor Cappa gives the nod to IFS, while Senior Editor Brubaker supports the solid axle.
IFS Will Out-Handle Any Solid Axle Suspension
I’ll admit, a solid front axle is anvil-simple compared to independent front suspension (IFS) and it can be more durable in the right environments, but the fact is that most of us don’t spend the majority of our time driving in those particular environments. Why punish yourself with rough-riding, antiquated solid-axle technology that you only need for a minuscule part of your drive time? If you want ride comfort and predictable handling at any speed on- and off-road, you simply cannot beat IFS with any amount of aftermarket wizardry thrown at a solid-axle front suspension. In my early years I remember being literally embarrassed off-road when a basic IFS (and IRS) VW Baja Bug would absolutely smoke any of the solid-axle trucks I owned over desert two track. Let’s look at the facts; the fastest, best-handling on- and off-road race vehicles have IFS suspensions. But you don’t have to be a racer to appreciate the attributes of IFS. IFS is simply more civilized than a solid-axle suspension. Because the left and right wheels are not directly connected via a solid beam, there will be less head toss in the cab over rough terrain. The tires and wheels are free to move independently when they encounter obstacles. You’ll even see more ground clearance on an IFS 4x4 than on a comparable solid-axle 4x4. It’s true that a solid axle can typically provide more articulation on an RTI ramp, but that’s only one measurement that has very little to do with overall trail performance. If you want to go off-road at any kind of speed over 5 mph, then an IFS is by far the way to go. If you plan to spend your entire life crawling at a snail’s pace over extreme rocky trails, plowing snow, drag racing, or truck pulling, then a solid axle may be for you. The rest of us will enjoy the benefits of the precision handling afforded by IFS.
If you want to go off-road at any kind of speed over 5 mph, then an IFS is by far the way to go.
Summary: IFS will handle and perform better than a solid axle in most on- and off-road environments. –John Cappa
Solid Axle Awesomeness
First off, I must say that I have driven some great riding and handling solid-axle trucks and SUVs. The one that comes to mind first is the ’11 Ford Super Duty F-250. The suspension engineers nailed it. At that year’s Pickup Truck of the Year competition, I was stunned by the trucks manners at speed, whether around town or off-road. Even with its unsprung axle mass, the truck offered up civility and function that was on par with IFS pickups in my opinion. That truck destroyed the argument that IFS has vastly superior handling and ride quality.
The simplicity, ruggedness, and swapability of the solid axle are second to none.
My biggest gripe with IFS is its complexity. A solid axle has less moving parts and is easier to service, with no crossmembers clogging everything up. I also don’t like that the centersection in many new IFS rigs is made of aluminum. Solid-axle centersections are typically cast iron, which is more durable. Some IFS systems also have weaker steering systems than solid-axle-equipped rigs. The solid-axle steering also isn’t susceptible to extreme camber and toe changes under load and cycle as an IFS rig.
Some IFS rigs utilize torsion bars, which can create a catch point off-road. And when lifting an IFS rig with torsion bars the bars either have to be lowered amidships or raised at the frontend to compensate for the lift. And speaking of lifts, a solid-axle rig is far easier and less expensive to lift than an IFS-equipped rig. And on the subject of modifications, let’s say you’ve added larger tires to your truck or you’re demanding more from it in a work environment. With a solid-axle rig you can get a larger centersection that is capable of handling more abuse by simply swapping in a heavier-duty axle. Not so with IFS. Unless you want to spend a boatload of money to re-engineer your entire IFS system (or swap to a solid axle) you have to stay with the differential that came on your rig.
When it comes to off-road travel, as one side of the solid axle is forced up or down, the other side is forced in the opposite direction. IFS doesn’t operate this way because each side is working independently. This means that the solid axle has more chance of traction than with an IFS rig.
Summary: In most situations the solid axle is the hot ticket for 4x4s, whether they’re used for work or play. The simplicity, ruggedness, and swapability of the solid axle are second to none. –Ken Brubaker