What's the difference between shocks and struts?

Are shocks and struts one and the same part?

Every vehicle on the road today has a suspension system made up of several individual parts, including shocks (or struts) and springs. The springs are designed to support the vehicle and cushion the ride when the vehicle hits objects on the road. Shocks (also known as struts) limit the vertical displacement or movement of the springs while absorbing or damping the impact of road obstacles.

People generally use the terms shock and strut to describe the same part because they perform the same function. However, there is a difference in the design of shocks and struts - and each has unique advantages and disadvantages:

The main difference between a strut and a shock is the design of each suspension system.

All vehicles use a shock absorber or strut at each of the four corners. Many use a strut in the front and a shock in the rear.

Struts are used in vehicles without upper control arms and are connected to the ball joint, while vehicles with upper and lower control arms (independent suspension) or a solid axle (at the rear) use shocks.

How shocks work?

Contrary to what many people think, conventional shocks do not support the weight of vehicles. On the contrary, the primary purpose of the shock absorber is to control the movement of the spring and suspension. It does this by converting the kinetic energy of the suspension movement into thermal energy that is dissipated by the hydraulic fluid.

The resistance developed by a shock absorber depends on the speed, the suspension, and the number and size of the tiny holes in the piston. All modern shocks are speed-sensitive hydraulic dampers, which means that the faster the suspension moves, the more resistance the shock provides. This feature allows shocks to adapt to different road conditions and reduce speed by :

• Bounce
• Rolling and swaying under the effect of worn shocks, losing the ability to control the rate of weight transfer.
• Braking dive and acceleration squat

Shocks work on the principle of fluid displacement, both in the compression and extension cycles. A typical car or light truck will have more resistance during its extension cycle than during its compression cycle. The compression cycle controls the movement of a vehicle's unsprung weight, while the extension cycle controls the heavier sprung weight.

What struts do?

The strut is a common type of shock absorber used in many independent suspensions, front-wheel-drive vehicles, and some rear-wheel-drive vehicles.

A strut is a major structural component of a suspension system. It replaces the upper control arm and upper ball joint used in conventional suspensions. By design, a strut is lighter and takes up less space than the shocks used in conventional suspension systems.

Struts serve two main functions.First, like shocks, struts have a damping function. Internally, a strut is like a shock absorber. A piston is attached to the end of the piston rod and acts against the hydraulic fluid to control the movement of the spring and suspension. Like a shock absorber, the valve creates resistance to the forces created by the up and down movement of the suspension. Like a shock absorber, a strut is speed-sensitive, which means it is equipped with a valve that increases or decreases resistance depending on the speed at which the suspension is moving.

Struts also perform a second function. Unlike shocks, struts provide structural support to the vehicle's suspension, holding the spring and tire in place. They also carry a large portion of the lateral load applied to the vehicle's suspension. As a result, struts affect ride comfort and handling, as well as vehicle control, braking, steering, wheel alignment, and wear on other suspension components.