2020 Subaru Outback Suspension Deep Dive | More than meets the eye

The 2020 Subaru Outback is a completely redesigned car. It has a lot to offer in terms of new convenience features, and the driving experience is much improved. A good deal of that comes from chassis improvements, and indeed a lot of work went into making the body shell and suspension subframes more rigid so the suspension attachment points could be more robust and stable.Don’t let all of that rigidity talk make you think the ride itself is stiff. It isn’t. Any suspension tuning engineer will tell you that a stable platform is necessary even if a smooth ride is the goal. Rigid attachment points make it easier to control ride motions and road imperfections within those components designed for that very job – the springs, dampers and suspension bushings.So let’s take a look at what Subaru has done under the new Outback. What we’re about to see doesn’t just apply to the Outback wagon, but to the closely-related and also-redesigned 2020 Legacy sedan as well. It’s no surprise that a vehicle like the Subaru Outback uses strut front suspension, but from here, a couple of details do look curious. Like any strut suspension, the steering axis (yellow line) is defined by the pivot bushing at the top of the strut and the center of the lower ball joint. The entire affair will pivot about this line when the wheels are turned.The lower control arm (red) of the newly redesigned 2020 Outback is now a lightweight aluminum piece instead of the steel hunk that was used last year. As before, there’s a “direct-acting” stabilizer bar link (green) that attaches to the strut housing, an arrangement that maximizes the efficiency of the stabilizer bar because the motion ratio is 1-to-1 motion with respect to wheel movement. As for the stabilizer bar itself, it’s now hollow to save a bit of weight. This spacer (yellow) raises the body relative to the suspension. The Outback has one, but the lower-riding Legacy sedan does not. The spacer pushes the arm down (or the body up - take your pick), so that means the Outback’s reinforcing bracket (green) will also differ from that of the Legacy.While we’re here, look at the round rubber bushing just below the spacer. That void space and square nub you see pointing directly at you will make sense in a short while. Subaru couldn’t simply put a spacer on the Outback’s rear lower control arm pivot and call it good. They had to do something of similar magnitude at the front. But the front subframe (green) is one big piece from top to bottom. What they did was slide a long flat spacer block (yellow) between it and the Outback’s body. It’s hard to see behind the spot weld seam that hangs down, but it is up in there – and it’s as thick as the spacer we saw in the last image. The Legacy doesn’t have this, so its subframe would look thinner because more of it would slip up and in behind the down-hanging body weld seam. The front and rear lower control arm pivots are braced with a broad plate (yellow) at the bottom to give these critical front suspension pivot points extra strength. Its forward edge has a big u-shaped gap, and that’s there to accommodate the passage of the flat-four engine’s exhaust system. The lower control arm has a distinct L-shape. The upward component – the shock – goes up into the spring and damper no matter what. Lateral cornering loads (yellow) will primarily act on the forward bushing of the L-shaped arm.But the load path changes when you hit a pothole or other sharp-edged bump because there is always a rearward component – the harshness. Here, the front bushing is more of a pivot point. The rearward impact at the ball joint (green) is turned through approximately 90 degrees to become an inward pulse at the rear bushing. This is where the bushing’s void and square nub we saw earlier come into play. Those features are calibrated to allow just enough give to take the edge off the incoming pulse while still maintaining control. It’s not surprising to see that the lower control arm’s inner pivot (yellow) doesn’t have any provision for camber adjustment. That’s never something you see on strut front suspensions with an L-shaped lower arm. That said, the Subaru Outback does provide a way to adjust camber. It’s hidden within the upper strut mounting bolt (green). Two-bolt strut mounts are fairly common, but they don’t usually give you any easy way to adjust camber. Struts aren’t meant to be adjustable, in most cases. Some parts catalogues will have “crash bolts” with smaller shafts that can be substituted if the need arises to provide slop that you can manipulate to make crude adjustments, but that’s a bad way to go for a number of reasons. Mainly, they don’t hold their adjustment well at all.Subaru’s approach is a more refined version of the crash bolt concept that’s far more stable. The lower bolt is just a bolt in a round hole, but the upper one (yellow) has an internal eccentric that rides in a vertical slot. You have to loosen both, of course, but once that’s done you can rotate the upper bolt head (on the hidden far side) to move the eccentric to make your camber adjustment. There’s never any in-and-out slop like there is with a reduced-diameter crash bolt, so the adjustment holds firm once you torque things tight. Even with the wheels on, you can always tell (or nearly always) if a vehicle’s steering linkage works ahead of the front axle or behind. In almost every case it’ll be opposite the side that the brake calipers are on. It’s easy to see how they can’t share the same space from this vantage point.Most front-drive-based crossovers will have front-mounted brakes and rear-mounted steering because a transverse engine and its transmission occupies the space where front-mounted steering would go. But the Subaru’s longitudinally-mounted flat-four engine allows for the use of front-mounted steering (green), and so we see rear-mounted brakes. From this vantage point we can also make out the dual pistons (yellow) that power these sliding caliper brakes. Even from this distance we can see that the rear suspension is most definitely not strut-based. There’s a nice aluminum upper wishbone, a coil-over spring/shock assembly, and a few other interesting bits. The aluminum upper wishbone is perfectly shaped to explain why these are often called A-arms. Its inner pivots, along with all of the other suspension members we’ll see shortly, bolt to a large steel subframe (green). This subframe has been thoroughly redesigned to be twice as rigid as last year’s, and part of that comes from its extensive use of a higher-strength grade of steel.That subframe is spaced away from the mounting points by large spacers (yellow) that raise the Outback’s body to provide extra clearance as we saw in the front. The related Legacy sedan rides lower even though it uses the same rear subframe because its spacers are much thinner to the point where they look more like washers. Down below, two separate links are arranged to approximate a wishbone. But “approximate” is the key word here. This is not a double wishbone suspension. It is a multilink suspension variant that employs a single upper wishbone and additional links.While the respective responsibilities of the two links overlap somewhat, the rear one (green) has more to do with lateral loads and camber control because it runs nearly square to the chassis. The front one (yellow) angles along the car’s length to a greater degree, so it is more involved in the fore-aft location of the lower end of the hub.Meanwhile, hiding quietly above them both, there’s a short toe link (red). Imagine the red and green links moving up together, as they would if the car were arcing through a right-hand corner, the body rolling to the left. The toe link would sweep through a tighter arc because it is the shorter of the two, and that would tend to pull the front of the tire inward to create roll-induced toe-in, a beneficial trait because it counteracts oversteer. This alternate view shows the same three links and the nice-looking aluminum hub carrier – also called an upright – that they all mount to. The toe-link’s inner pivot (yellow) is where you’ll find an eccentric to set static toe-in. The rear hub (yellow) looks very tidy and organized. The rear brake hose is nicely anchored with a steel bend that’s bolted to it, but then it switches back to rubber and connects to the brake caliper through a graceful bend. Why is it there? So you can easily hinge-open the sliding caliper and replace pads without undoing any hydraulic lines. You’re doing it wrong if you ever consider breaking the hydraulics open when changing brake pads. Our rear lower link does a lot more than simply help locate the wheel in space. It also carries the load of the coil-over spring/damper assembly (yellow), not to mention the weight of the car pressing down from above. Because of this we’ll elevate its status from link to control arm. The rear stabilizer bar (yellow) also feeds into the lower control arm. Further inboard, the inner pivot of the lower control arm lacks any provision for rear camber adjustment. The outer end of the Outback’s lower control arm moves in lock-step with the wheel and the inner pivot doesn’t move at all. The spring and shock mount roughly 80 percent of the way out, so those will compress 0.8 inches for every inch of wheel travel, more or less. The stabilizer bar bolts to the arm about 60 percent of the way out, so its motion ratio is about 0.6-to-1. The Outback rides on 18-by-7-inch aluminum alloy wheels with a 55 mm offset and 225/60R18 Yokohama Avid GT BluEarth tires. The assemblies weigh 53 pounds apiece, which is about par for the course. In off-road-speak, that size works out to just under 29 inches tall, which is pretty healthy. There are those that put bigger all-terrain tires on Outbacks, but one must be very mindful of not going overboard whenever strut suspension is present. The limiting factor, which you can’t do much about, is the clearance between the top of the front tire and the strut’s lower spring perch.The Outback offers a surprising amount of off-road clearance, and it’s interesting to see how much of that was gained by simply spacing the body higher atop suspension components that have a lot in common with the Subaru Legacy sedan. I’m sure there are numerous other differences that didn’t show themselves in this exercise, such as possible changes to the length of the steering shaft and various wiring harnesses, but the main elements of the change, at least, are plain to see.Contributing writer Dan Edmunds is a veteran automotive engineer and journalist. He worked as a vehicle development engineer for Toyota and Hyundai with an emphasis on chassis tuning, and was the director of vehicle testing at Edmunds.com (no relation) for 14 years.Read more Suspension Deep Dives below and let us know which cars you'd like to see Dan put up onto the jack stand next ...Toyota GR Supra Suspension Deep DivePorsche Taycan Turbo Suspension Deep DiveToyota 4Runner TRD Off-Road Suspension Deep DiveFord F-250 Tremor Suspension Deep DiveJeep Wrangler Rubicon Suspension Deep DiveRelated Video:Filed under: Subaru,Deep Dive,Crossover,Wagon,Off-Road2020 Subaru Outback Suspension Deep Dive | More than meets the eye originally appeared on Autoblog on Wed, 1 Apr 2020 12:00:00 EDT. Please see our terms for use of feeds. Permalink | Email this | Comments