2009 Dodge Challenger R/T: Suspension Walkaround
There's more to the 2009 Dodge Challenger than a retro body and a 5.7-liter Hemi V8. It's got a modern suspension inside those full-figured wheelwells, and there are a couple of surprises.
Here we can see coil-over suspension (white), a high-mount upper control arm (green) and a forward-mounted steering rack (black). Other than the fact that it's all steel, it's the same basic layout and the 370Z and the Infiniti FX50. But the Challenger has something extra that those two don't have.
Down below, the front suspension has a dual pivot arrangement (yellow) like we've seen before. But our Challenger is the first car we've looked at in the Walkaround series that pairs this design with the high-mount upper control arm. It's a desireable combination: The high-mount upper arm provides a better camber curve than a strut, and the dual pivot arrangement and it's zero scrub radius makes for more stable and kickback-resistant steering in bumpy corners.
The Challenger R/T has two-piston sliding front brake calipers (orange) and ventilated brake rotors.
The stabilizer bar (white) connects to the coil-over shock unit in such a way that makes it appear as a direct-acting mount with a 1:1 motion ratio (yellow). But that's not the case because the coil-over in turn attaches to the lower link (green) at a point inboard of the ball joint. As a result the spring, damper and stabilizer bar share the same motion ratio of approximately 0.72:1 or so.
Modern catalytic converters (white) are mounted as close as possible to the exhaust headers so they "light-off" quickly to reduce emissions as quickly as possible after a cold engine start. Here that puts them close to the stabilizer bar bushings, which are made of rubber. A heat shield (yellow) surrounds and protects each one.
One of the advantages of forward-mounted steering racks (those mounted ahead of the front wheels instead of behind them) is that their relative distance away from the driver allows the pinion to be reclined to point more-or-less directly at the driver, thereby producing small universal joint angles in the steering shaft. Smaller U-joint angles allow for smoother and more direct steering feel.
As we've come to expect, the upper arm geometery includes a healthy dose of anti-dive.
Moving to the rear, we see the Challenger has a straightforward 5-link multilink independent suspension. The two upper links (yellow) sit more-or-less above the two lower ones (green). As we've seen before, one of the the lower links is spread wide to carry the spring. The fifth link (black) is a toe-control link. The rear stabilizer bar (white) loops in from the top to keep clear of the upper links.
The rear brake rotors are ventilated, and the calipers are single-piston sliders.
Even though it doesn't seem like much at first glance, this is probably the most unexpected and interesting aspects of the our Challenger R/T's suspension. And the only reason our Challenger R/T has it is because it has the 6-speed manual transmission.
Let me explain.
Those humungous shock absorbers are not ordinary shocks. In fact they are self-levelling units called Nivomats by the company that makes them, Sachs. These are typically found at the back end of minivans, wagons and SUVs -- vehicles that see a lot of rear axle load when all the people pile in or when a trailer is latched on.
Nivomats a very high pressure monotube dampers, but they also function as adjustable rate springs that have internal ports that vary the amount of support they give based on how far the suspension is compressed. If you add load and compress the suspension, the motions associated with driving "pump" them up using pressure stored in an internal accumulator. Unloading the trunk of a car with "pumped" Nivomats will result in an overly-raised "ass-up" attitude, but that simply exposes a second internal port that drains fluid back into the accumulator until equilibrium is restored.
Sound complicated? It is. All you have to know is that Nivomat load leveling shocks are self contained, with no compressor or external connections of any kind.
In a typical Nivomat installation, only 65 to 75% of the rear spring duties are carried out by the actual coil springs (yellow); the remainder is carried-out by the Nivomat unit (red) itself. What that means is that you can't simply toss-on any aftermarket shock in an attempt to tune your suspension because this Nivomat is an essential part of the spring force that supports the rear of the car. It has to stay here at all costs unless you put on new springs that can go it alone without Nivomats.
All of this begs the question: What is a pair of load-levelling shocks doing on the back of a 2009 Dodge Challenger R/T? And why do they only appear on the manaul transmission version?
I had to talk with Dodge engineers to figure that one out, because I'd never seen them used this way before. Turns out that Nivomats are very good at combatting axle hop during hard drag-style launches. They help put the power down when you drop the clutch. They're not necessary on automatic-equipped R/Ts because torque delivery is muted through a slushbox -- they don't launch as violently as a manual.
So that's a second reason why you want to leave these babies alone if you throw aftermarket "upgrade" parts at your suspension. And when it's time for new shocks on an unmodified car, you'll need to buy new Nivomats.
There is a bit of aluminum (orange) in the rear suspension, and it's found in the form af an aluminum rear hub carrier (aka knuckle).
The toe link (geen) has an eccentric for adjustment on its inner end, back under the car where we can't see it here. And the stabilizer bar attaches directly to the knuckle via a long slender link (yellow) that gives it a 1:1 motion ratio.
The Challenger has a lot more suspension going for it then you might think, on paper at least. But our R/T doesn't exactly inspire everyone in the office with its legendary handling. Steady? Yep. Secure? You bet. Predictable? Of course. But the killer instinct isn't quite there. There's probably a few reasons for that.
First, the Challenger isn't exactly svelte. This one weighs over 4,050 lbs. It's a sizeable car.
And I have to think the tires are playing a huge role, too. It's not that they weigh 54.5 lbs apiece when mounted on their 18 x 7.5" wheels -- those numbers aren't terribly problematic.
The problem stems instead from the tires themselves, a mid-line Michelin HX MXM4. Their 235 mm width isn't terribly inspiring for a 2-ton car, either.
And whenever you see "green" on a tire, you can bet that high performance wasn't at the top of the development priority list. Between the narrow width and the low rolling resistance design, it seems likely that Dodge was trying to make sure they got the best fuel economy rating they could from the R/T to make sure they didn't run afoul of CAFE regulations.
And don't forget that the R/T isn't the model Dodge is marketing as the high-performance model. They probably want to maintain a meaningful performance gap between this and the SRT8.
I figure that a set of focused high-perforamnce tires might make a bigger-than-usual difference on this car. And if I can talk Scott into it, we might just test my theory ourselves.
Dan Edmunds, Director of Vehicle Testing @ 4,695 miles