Toyota 4Runner TRD Off-Road with KDSS Suspension Deep Dive

The 2020 Toyota 4Runner represents the 11th year of a fifth-generation design that debuted as a 2010 model. So it's not new, but that also doesn’t stop it from being more successful than ever. Sales have been on the rise every year since, with a notable spike in 2015 after it got a minor facelift and a freshened dashboard. There were welcome tech updates for 2020.

However, nothing much has changed on the mechanical side in all of that time. Why is that? The answer has two parts. The competition has morphed into crossovers, leaving the 4Runner as one of the last truck-based SUVs standing. It’s also legendary in its own right when it comes to off-road performance and durability. Instagrammers and Overlanders, as well as those who follow Overlanders on Instagram, seem to be magnetically drawn to it.

The one that best encapsulates this vibe is the TRD Off-Road (known as the Trail before 2017), a thoughtfully-equipped model that occupies the second rung in the price ladder. There’s no doubt the TRD Pro is a nice piece, but the TRD-Off Road is far less expensive, much easier to find, and it still has the same locking rear differential, Crawl Control, and the Multi Terrain Select traction control optimization system.

Sure, you won’t get the Pro’s knobbier tires and tricky shocks, but you can replicate both in the aftermarket and still have a good chunk of money left over. And the TRD Off-Road offers a potent option you can’t get on the Pro: KDSS, the Kinematic Dynamic Suspension System. Let’s take a deep dive into the suspension of a 4Runner TRD Off-Road with KDSS.

The 4Runner’s front suspension is very similar to that of the Toyota Tacoma, the dearly departed FJ Cruiser and even the Lexus GX. All of the parts aren’t necessarily interchangeable, but they all use a double wishbone layout with coil-over shocks that is functionally the same.

It takes five links to locate a wheel in space, but each use of an A-shaped wishbone counts as two. Front suspensions obviously need to turn, so the fifth link is always the steering linkage (yellow arrow). This one is mounted ahead of the front axle, a position that is generally thought to be superior. It’s also easy to execute when the engine is mounted longways, as it is in trucks and truck-based SUVs like the 4Runner.

The upper wishbone is mounted high, a position that reduces the load on the arm and its bushings, and makes it easier to optimize steering and camber geometry. Here the pivot axis is angled steeply down toward the rear, an arrangement that produces an anti-dive effect that works against the tendency for nose-dive under braking.

The lower wishbone (yellow) is hard to see here because every system wants a piece of it. The coil-over shock (green) bolts to it after it necks down to sneak past the driveshaft, but the elephant in the room is the massive and weird-looking front stabilizer bar (red) running along the front edge.

Most 4Runners (and all Tacomas) have a smaller front stabilizer bar that loops over the top of the steering to connect with the open hole (blue) in the steering knuckle via a linkage. But this 4Runner has KDSS, which features a larger bar that runs along the front of the lower wishbone and is attached to it directly with an unusual bushing and clamp arrangement.

You want KDSS whether you’re going off-road or not. The system is essentially a pair of fatter stabilizer bars that are better at suppressing body roll (and upset stomachs) on winding roads. But such high roll stiffness is usually terrible off-road, where wheel articulation is king. The magic of KDSS is that it can sense these situations and let the bars go limp and effectively “disappear” at the opportune moment without driver intervention.

The direct bolt-on mounting we see here is central to the way it works.

Normally, stabilizer pivot points are fixed rigidly to the frame and the links that connect to the moving suspension elements are out on the free ends. But you can switch that around if you attach the bar ends to the suspension directly. Here the KDSS stabilizer bar’s pivot points are floating on links, with an entirely rigid one on the passenger side (yellow) and a hydraulic cylinder (green) on the driver side.

The hydraulic side stays rigid on paved roads, and that holds the bar’s pivot axis firmly in space so the stabilizer can offer twisting resistance to counteract vehicle roll in corners. Moguls and other lumpy off-road terrain causes the cylinder to go limp, and that allows this corner of the bar to move up and down freely. This action destroys the bar’s ability to generate any roll stiffness, which is a boon to off-road wheel articulation.

The end result is the same as the push-button stabilizer bar disconnect system on the Jeep Wrangler Rubicon, but the method is entirely different and there’s no button to push. But it’s more than that. The ability to disconnect a stabilizer bar means you can mount a fatter one in the first place, and that’s why a KDSS 4Runner corners flatter on winding roads and is better able to handle, say, a rooftop tent than a non-KDSS 4Runner. That same KDSS 4Runner will also articulate better when driven off-road despite its bigger stabilizer bars.

There are downsides. KDSS costs $1,750. It comes with a front skidplate that hangs down a little more to allow for the expanding motion of the front strut. There’s also a limit to how much you can lift a KDSS 4Runner. Estimates vary, but 2 inches seems to be the maximum.

The front bump stop is a rubber chunk that gets squished into the lower wishbone. Those concentric cuts help to make the engagement a bit more progressive, but the specific reason for the pebbly texture escapes me. If I had to guess, I’d say noise reduction.

All 4Runners come with sizable front brakes that consist of ventilated front rotors and 4-piston fixed calipers. They employ an open window design, which means a routine brake pad change is a simple matter of removing a pair of pins (yellow) and pulling the pads straight out. As ever, you’ll have to unbolt and remove the caliper if the rotor needs attention.