What is the difference between shocks and struts?

Shocks and struts are both key components of a vehicle’s suspension system, but they serve slightly different purposes and are designed differently. Here’s a closer look at each one, their functions, and the differences between them:

What Are Shocks?

Shocks (short for shock absorbers) are hydraulic components designed to dampen and control the impact and rebound of the vehicle’s springs and suspension. Their primary purpose is to reduce bouncing, absorb road impacts, and help keep the tires in contact with the road.

Construction: Shocks are typically made up of a piston that moves through oil inside a cylinder. As the suspension moves, the piston pushes through the oil, creating resistance and slowing down the motion.
Function: Shocks don’t support the vehicle’s weight; instead, they control the movement of the springs and suspension. By absorbing energy from the suspension’s movement, shocks prevent the vehicle from bouncing excessively and help improve ride quality and stability.
Placement: Shocks are used on vehicles that have separate spring and shock systems. Many trucks and older cars have shocks paired with either coil springs or leaf springs.

What Are Struts?

Struts are more complex components that combine the shock absorber and some structural components into a single assembly. They provide support to the suspension and play a direct role in aligning the vehicle’s wheels.

Construction: A strut is essentially a shock absorber integrated with a coil spring and other components, like the spring seat, strut bearing, and a steering knuckle in front suspension systems. This makes it a key structural component of the suspension.
Function: Struts perform two main functions: dampening (like shocks) and structural support. They help bear the vehicle’s weight, assist with alignment, and play a crucial role in the steering and handling of the vehicle.
Placement: Struts are commonly found in the front suspension of most front-wheel-drive vehicles, but some rear-wheel-drive and four-wheel-drive vehicles also use struts. They replace the need for an upper control arm, making the suspension more compact and lightweight.

Key Differences Between Shocks and Struts

Aspect	Shocks	Struts
Function	Controls suspension movement, reduces bouncing	Controls movement, supports weight, and provides structural support
Design	Separate component from the springs	Integrated with coil spring and other components
Role in Suspension	Dampens motion of the springs	Dampens motion and supports structural integrity
Impact on Alignment	No direct effect on wheel alignment	Directly affects wheel alignment and camber
Cost of Replacement	Typically less expensive and easier to replace	Generally more expensive and complex to replace due to integrated components

When to Replace Shocks vs. Struts

Both shocks and struts wear out over time and should be replaced when they show signs of wear, such as:

Excessive bouncing or swaying when driving
Nose-diving when braking
A rough or bumpy ride
Fluid leaks from the shock or strut
Uneven tire wear
Unusual clunking or rattling noises

Shocks generally last between 50,000 to 100,000 miles, while struts, because they are more structurally integrated, may have similar lifespans but often require more careful inspection and maintenance.

Can You Replace One Without the Other?

Shocks and struts are often replaced in pairs (front or rear) to maintain balanced performance, but you don’t need to replace shocks if only struts are worn out, and vice versa. However, it’s generally recommended to replace them in pairs (e.g., both front shocks or both rear struts) for balanced handling and even wear on the suspension components.

In summary, while both shocks and struts control suspension movement, shocks primarily dampen motion, while struts combine that function with structural support, alignment control, and load-bearing capabilities. Proper maintenance and timely replacement of both components help ensure a smooth, safe ride and better handling on the road.