Like other components on your car, shocks will eventually wear out. Replace them if your car bounces excessively over bumps, or if you notice oil leaking out of them. It may seem like you’re just giving up a bit of ride quality if you don’t change them, but when shocks get bad enough, they can affect how your tires contact the road. It’s possible you could lose control in certain situations, such as if your vehicle hits a bump and bounces when you’re trying to negotiate a curve or make a lane change.
Regular shock absorbers do adjust to the road surface; on a harder bump, the shock’s internal piston will move more, and encounter more resistance from the hydraulic oil. But there are also shocks that can be adjusted by the driver for a firmer or softer ride, and systems that automatically adjust depending on road conditions.
Ford, which adds an adjustable system to its 2017 Fusion Sport, uses electrohydraulic shocks. “Instead of having a fixed set of mechanical valves that defines the response of the damper at all times, we have an additional valve,” says David Russell, vehicle dynamics technical specialist at Ford. “The valve is actively controlled and adjusted by sensors in the vehicle. We use 46 inputs to decide how much to tighten or open that additional valve. It goes through those inputs 500 times per second, and it takes 10 to 20 milliseconds for the damper to achieve the new target.”
Controlled by an electric actuator, the shock reacts to input from the vehicle as it measures such considerations as the vehicle’s speed and the driver’s steering input. The shock also changes its character when the driver hits the “Sport” button on the console. On some vehicles, this only changes the driveline performance, such as holding the shifts longer on an automatic transmission. But on a vehicle with an adjustable suspension, it can also change the way the shocks react, making them firmer in sport mode.
Even 10 milliseconds might seem like an eternity to some drivers. To get even faster results, some automakers, including Ford, GM, Ferrari and Audi, among others, offer shocks that use magnetic force to dampen the ride, rather than a valve. Developed by GM’s Delphi division and first used on vehicles in 2003, and now owned by BMI Group, MagneRide uses fluid that contains tiny iron particles, along with an internal piston that contains electromagnetic coils.
Under normal driving, the particles are disbursed evenly throughout the fluid. But when the shock needs to tighten on a bump, the car sends an electrical current to the coils in the piston, which magnetizes it. This almost instantly aligns the particles, increasing the resistance and keeping the ride controlled over the rough patches. If the shock needs to be even firmer, the system adjusts the current to make the magnetic field stronger, increasing its effect on the particles. The shock works entirely on electricity, rather than on mechanical valves. While the effect is the same — the shock reacts to input as the car moves down the road — it can adjust itself some five times faster than one with valves.