Latest Cybertruck Teardown Reveals Tesla’s Odd Sway Bar Decisions, Clever Packaging

Teardowns of the Tesla Cybertruck continue apace at Munro & Associates. This week, Sandy Munro’s automotive benchmarking firm has released a video on the Cybertruck’s rear cradle and electric drive module (EDM).

As seen in previous teardown videos, Munro sourced a tri-motor Cyberbeast for his company’s teardown efforts. Thus, this example has a tightly-packed electric drive module (EDM) in the rear. Along with the dual rear motors and supporting inverters, there’s also the rear steering module hanging on the rear cradle to boot.

This latest teardown on the Munro Live channel is hosted by Jordan Arocha, at Munro & Associates, along with lead engineer Kevin Harty. The duo step through a series of interesting tidbits in the rear cradle design, particularly concerning the suspension and steering layout.

The Non-Michael Mann Kind Of Heat

The layout is neat and organized, with the EDM hosting two motors with two plate coolers on top. The cooling circuit is also plumbed to feed the inverters, too. Jordan notes that cooling for the EDM is handled both with the gearbox oil and ethylene glycol.

Jordan also suggests Tesla may be netting some additional functionality by using the motors to generate heat when needed. “When you wanna heat the vehicle up, what previous Teslas would do is…  they would stall out the motors, that would create heat within the unit,” says Jordan. “They would use the remote electric pumps to plumb oil into the plate cooler, to heat up the ethylene glycol, to ultimately heat up the battery.” He notes this can help eliminate the need for separate heaters to control battery temperatures. He suspects the Cybertruck may be relying on a similar system.

“Every exposed surface for the heat exchanger here is machined, which is interesting obviously and expensive,” says Kevin. It’s not entirely clear why this is done. By machining and then peening or swaging the parts, they may be creating a better thermal connection between parts of the inverter housing. This could have something to do with maximizing cooling for the insulated-gate bipolar transistors within the inverter. They deliver power from the battery to the motors and must be kept cool to avoid failure. “Keeping them cool is critical for EV performance,” says Kevin. “If you wanna go fast, and go fast for a long time, it’s imperative to keep them cool.”

Structural Concerns

The sway bar stands out right away on the rear cradle. “One thing we were talking about is the sway bar, and the fact that it might be a little bit ad-hoc or they might need a little additional locating retention for the sway bar itself,” says Kevin. We can see band clamps holding a rubber isolator around the swaybar to keep it from shifting left and right.

Kevin notes that more integrated methods are more typical for locating the sway bar in the correct position. “[It’s] something that I would say is not the most elegant execution in terms of the bushings,” says Jordan. “This is likely quite a manual operation to get these bushings on. That’s not great practice for a very high-volume application.”

Kevin notes that the rear cradle design is similar to front cradles in other contemporary vehicles. The rear upper control arms are mounted to the gigacasting on the vehicle, while the rear cradle can be dropped out without them. “They’re using the gigacasting that they bought and paid for to complement the structure of the cradle itself,” says Kevin. Jordan notes that when Tesla updated the Model Y in 2022, the front upper control arms were mounted directly to the gigacasting up front. The Cybertruck does the same thing in the rear.

Packaging is tight around the rear drive assembly, which Kevin notes could have an impact on maintenance down the road. “It might just be easier to dedeck the entire cradle if you’re replacing bushings, to do everything at once,” he says. It makes sense—dropping the rear cradle out of the vehicle would provide far more room for pressing out old bushings and installing new ones.

The rear cradle also mounts the rear steering rack. Jordan notes the unit carries Tesla branding cast into the body. “I don’t know if they’re building it in-house, but I would suspect it might be,” says Kevin. “It’s overall packaging size, [and] the way it’s laid out is definitely atypical and different from what we’ve seen in the past from suppliers like ZF.” The rear suspension layout features an upper control arm and lower control arm, with the steering link playing a role, too. It helps control toe in addition to actually steering the rear wheels, Jordan explains.

It’s also obvious the Cybertruck has massive disc brakes, which is no surprise given its hefty kerb weight of 6,843 pounds. The Cybertruck uses a large cast rotor, with some holes machined in to save weight where possible. It might seem insignificant in the grand scheme of things, but even shaving off a few grams can have a benefit when it comes to cutting unsprung weight.

There’s also a little threaded hole in the wheel hub which lines up with a hole in the rotor. It appears to be an assembly aid for keeping the rotor in place before the wheel is mounted. Jordan notes that many automakers use similar features, where a small bolt holds the rotor to the hub while on the assembly line. Many automakers will leave these in place on production vehicles. Tesla is either not installing these bolts on the production line, or removing these bolts after they’re no longer needed. Jordan suspects Tesla might be removing the bolts to save costs, while Kevin jokes that it may just have been dropped and lost at some point.

Moving on to the lower control arm, Kevin notes the welded assembly and the difficult packaging job involved. “I’m a little surprised they didn’t try to get the sway bar link bolted through on the control arm,” says Kevin. He suspects tight packaging constraints may have played a role. Instead, the sway bar link is mounted on a separate bracket welded to the control arm assembly.

Jordan also notes that the four-wheel steering creates a much wider range of wheel positions through compression and turning, complicating the packaging job at the rear. This could have influenced the placement of components like the sway bar link mount. “That structure’s got a finite amount of real estate in which it can reside, ” says Jordan. “With that four-wheel steer, you’re really starting to encroach here and limit where this control arm can package based on where that wheel envelope is.”

Also notable are the long spans between the inboard pivot point and outboard point on the control arms. This is a common design choice on vehicles designed for off-road use. “That’s gonna allow you allow a lot more travel on your suspension,” says Jordan. “By going further inboard with those, it’s gonna reduce the amount of acute angles that need to be present for both the bushings as well as the half shafts.” Reducing those sharp angles tends to put less strain on CV joints and bushings, and keeps everything happier for longer.

Kevin notes that the Ford Raptor and Ram TRX are based on production trucks, and have to compromise in this regard. The only way to get similar travel and height on those trucks is by using longer control arms, which means widening the truck. Hence, these vehicles have added flares to deal with the added width. In contrast, the Cybertruck has long-span control arms baked into the suspension design out of the box.

Jordan notes that an EV provides more flexibility in this regard to rear suspension design, versus a traditional ICE drivetrain. Furthermore, having the gearboxes for the dual rear motors offest to the rear helps as well. It makes it possible for the two output shafts from the drive unit to be tightly packaged close together. This allows for longer half-shafts that can run at less acute angles. “The further away from the driven point on the motor to the hub that you can get, the better off you are,” says Jordan.

Ultimately, there weren’t any grand discoveries that were found lurking in the rear cradle of the Cybertruck. Deeper investigation may reveal dark magicks in the inverters or motors themselves, or other tricks besides. In any case,  when we know about it, you’ll hear about it here first at The Autopian.