Shocks and struts are crucial components of a vehicle’s suspension system, responsible for maintaining tire contact with the road. This contact is vital for effective steering, handling, and braking. Ride control products ensure optimal performance by managing body and tire movement, reducing bounce, roll, sway, brake dive, and acceleration squat. They also help preserve consistent handling and braking, maintain wheel alignment, and minimize premature wear on tires and suspension parts.
Shocks vs. Struts: Key Differences
While often used interchangeably, shocks and struts are distinct with unique functions. Shocks are individual components within the suspension system, whereas struts are major structural components of the chassis and suspension system.
Understanding the Role of Shocks
Contrary to popular belief, conventional shock absorbers don’t support vehicle weight. Their primary function is to control spring and suspension movement. They achieve this by converting the kinetic energy of suspension movement into thermal energy, which is then dissipated through hydraulic fluid.
The resistance provided by a shock absorber depends on the suspension’s speed and the size/number of orifices in the piston. Modern shock absorbers are velocity-sensitive hydraulic damping devices; the faster the suspension moves, the more resistance the shock absorber provides. This allows them to adapt to varying road conditions and minimize bounce, roll and sway (caused by worn shocks losing their ability to control weight transfer), brake dive, and acceleration squat.
Shock absorbers function via fluid displacement during both the compression and extension cycles. Typically, cars and light trucks exhibit greater resistance during the extension cycle than the compression cycle. The compression cycle manages the vehicle’s unsprung weight motion, while extension controls the heavier sprung weight.
Inside a Shock Absorber
Shock absorbers are essentially oil pumps. A piston, connected to the piston rod’s end, operates against hydraulic fluid within the pressure tube. As the suspension moves, the hydraulic fluid is forced through the piston’s orifices, which restricts the fluid flow. This restriction slows the piston, thereby slowing spring and suspension movement.
The Function of Struts
Struts are a common damper type found in many modern independent suspension, front-wheel-drive vehicles, and some rear-wheel-drive models.
A strut is a significant structural element of the suspension system. It replaces the upper control arm and upper ball joint used in conventional suspensions. This design makes struts lighter and more compact compared to shock absorbers in traditional systems.
Struts serve two main purposes. First, they provide damping, similar to shock absorbers. Internally, a strut resembles a shock absorber, with a piston connected to the piston rod working against hydraulic fluid to manage spring and suspension movement. Like shock absorbers, valving generates resistance to the suspension’s up-and-down motion. Struts are also velocity-sensitive, adjusting resistance based on suspension speed.
Secondly, struts offer structural support for the vehicle’s suspension, support the spring, and maintain tire alignment, unlike shock absorbers. They also bear a significant portion of the side load applied to the vehicle’s suspension. As a result, struts influence ride comfort, handling, vehicle control, braking, steering, wheel alignment, and wear on other suspension components.
Strut Components Explained
Struts typically consist of a strut housing, which provides rigid structural support for the assembly, and a damping unit within the housing to control spring and suspension movement. On most struts, the bottom of the body attaches to the steering knuckle, which connects to a lower control arm through a lower ball joint.
A complete strut assembly includes all components needed for strut replacement in a single, pre-assembled unit. It combines the strut housing, damping unit, and a coil spring to support the vehicle’s weight.
Shocks or Struts: Which Does Your Car Have?
Each wheel on your vehicle will have either a shock or a strut. Your vehicle might have shocks in the front and struts in the rear, or another configuration entirely. The crucial point is that every wheel has some form of ride control component.
