In the case of the 2022 Rivian R1T electric pickup, delivering a truck that drives like no other—see our First Drive review for more—required designing a suspension that works like no other. Well, it actually works a lot like the suspension of the McLaren 720S in that it includes hydraulic cross-linking of the adaptive dampers. The Rivian’s setup also shares the concept of using ride-height-adjustable air springs with several higher-end trucks and SUVs. But combining these elements gives the Rivian R1T several key advantages.
Designing an electric “adventure vehicle” with sufficient range to encourage true overlanding necessarily requires a big battery pack, which drives a high curb weight. A high payload capacity is also essential to accommodate gear and fellow adventurers, and variable ride height is key for conquering the toughest trails. Air springs are the best way to accomplish these goals, but as they inflate—whether to compensate for load or to increase ground clearance—the spring rate increases.
Ride quality is determined by how well each corner’s shock damping and spring rates are matched, so maintaining reasonable ride quality with variable-rate springs obviously requires variable-rate dampers.
Meanwhile, limiting body roll on pavement while enabling extreme suspension articulation off-road requires some sort of variable roll control system. Rivian’s hydraulic cross-linked suspension, designed and tuned in-house, employs variable-orifice valves to match the damping and spring rates while balancing roll control and articulation needs without adding heavy, costly, (and sometimes power-consuming) variable-rate or disconnecting anti-roll bars. Here’s how Rivian’s system works:
Monotube External Reservoir Shocks
These true monotube shocks include external reservoirs, as all the best off-roading shocks do. The internal piston incorporates no valving. Rather, as the wheel articulates, the hydraulic shock oil gets forced in and out of the upper and lower chambers, passing through variable-orifice valves that instantly adjust the flow rate that controls jounce and rebound. There’s a third valve at each corner that provides a connection to the central valve body that hydraulically interlinks the various corners to provide roll control.
A Rivian chassis controller constantly monitors driver inputs, road conditions, driving mode selection, and the various sensors that keep tabs on wheel position, vehicle load, and more. It uses this information to instantaneously determine the optimal degree of roll control or suspension articulation and sends this information to the central valve body. This device directs hydraulic pressure to where it can best be used.
The pressure is primarily generated by the upper chamber of the damper(s) experiencing jounce—for example, the outboard dampers during a cornering maneuver. Sending this pressure to the rebound chambers on the opposite side (inboard during cornering) counteracts body roll. Note that there is also a hydraulic pump that tailors the overall system pressure to suit various driving modes, increasing it in Sport mode, for instance. This effectively provides variable roll control front and rear. We are unaware of another factory off-roader with a variable or disconnecting rear anti-roll bar but welcome your feedback on that score.
Fully opening these valves and setting the shock-mounted jounce/rebound valves to their most open position allows maximum articulation and the softest ride. The various valves can, of course, be instantly firmed up to prevent float and to manage body motion after a bump or swell in the road.
The system is considered “semi-active.” There are no cameras reading bumps ahead, and there is no means to drive a wheel down into or pull it up out of a bump. But millisecond response time delivers lightning-quick damping and roll-control adjustment, which allows the suspension to deliver optimum ride quality right up until driving or road conditions demand firmness—all while tailoring the damping rate to suit the spring rate under all conditions.
In-House Design Using Best Possible Components
Rivian is rightly proud of the fact that its own engineers did 100 percent of the design, development, and tuning of this new suspension, utilizing components sourced from top-tier suppliers. The variable-orifice shock valves, for instance, come from Öhlins of Sweden, while the central valve body block is sourced from Tenneco, which supplies a similar unit to McLaren.
Proof of the Pudding Is in the Wheeling
We put thousands of miles on an R1T under the most demanding conditions on the TransAmerica Trail—rocks, mud, washboard roads, rutted gravel, sand—and came away amazed by the truck’s composure and comfort. The off-road mode affords the greatest comfort when the terrain turns lumpy, and this might also be the best mode for tackling weather-ravaged urban roads of the Midwest. We even had the opportunity to experience the truck without roll control, when a fault in one of the right-side corners in a prototype vehicle caused just that feature to go offline. The difference it makes is dramatic. And the fact that technicians were able to replace the strut in a parking lot in a matter of hours suggests Rivian may have the hardware and crew it takes to tackle the world’s most famous off-road race in Baja California, Mexico.
Source: Read Full Article