Numerous systems go into making a high-performance car, and while a powerful engine is almost always one of them, engineers never forget about the suspension. What’s a lot of power good for if it handles like a sloppy mess?
The McLaren 720S uses a very neat system, although it’s mighty complex. Thankfully, we have explainer extraordinaire Jason Fenske of Engineering Explained to help us digest the trickery going on. McLaren calls its setup the Proactive Chassis Control II, and namely, it uses fluid in the dampers. The system also foregoes the need for an anti-roll bar since the two dampers are interlinked.
At its core, the suspension uses the fluid to keep the care flat through corners. For example, when the car makes a hard left-hand turn, which will make the right side of the car want to come up as the car leans into the corner. Inside the damper on the right side, a piston presses fluid to force it to travel to the other side. This side is trying to extend as the car tries to roll, but the traveling fluid pushes the other piston up to bring the tire closer to the body of the car. So, the 720S stays flat in the corner from the force applied in the suspension.
What makes the whole system tick are flow restrictors fitted at each area where the fluid exits. The restrictors allow the fluid to either exit really quickly, or not, which changes the stiffness of the suspension. For example, a lot of restriction will make for a stiffer setup, while less restriction will make the car feel softer. Inside the restrictor is a needle valve, which controls how much, or how little, fluid leaves. This corresponds with Normal, Sport, and Track modes.
Applying this knowledge to the entire car, there are a couple of scenarios that explain why McLaren has the full system interlinked with each other. Warp is when the front and rear axles experience roll in opposite directions. Think of this kind of scenario on roads with different bumps and imperfections where the front doesn’t experience the same thing as the rear. Ideally, this requires the car to have some roll to allow the car to adapt, but too much body roll is never a good thing.
So, the suspension setup provides a place for pressure to go since there’s an opposite reaction at both ends of the car. If the front wheel wants to come up, high pressure is sent to the back wheel where there’s low pressure to try and create an equilibrium of sorts. This ensures the tires still have good contact with the road and the car adapts to changing surfaces.
We’ll let Jason take it from here as there’s a lot to learn about McLaren’s fascinating system.