(Updated on December 26, 2022)
Shocks, struts, and coilovers are part of most modern suspension systems. The suspension gives your vehicle its handling characteristics and ride quality. There are many different suspension implementations on different types of vehicles.
Some designs compromise handling in favor of ride comfort. Others prioritize handling above all else, which can give the driver a jarring experience over broken pavement. Each suspension architecture has its own pros and cons. The use of struts and shocks is factored into these design decisions before the vehicle even rolls off the assembly line.
Are Shocks and Struts the Same Thing?
Although they serve a similar purpose, struts and shocks are not the same thing. Here are some of the difference between shocks, struts, and coilovers.
Shocks vs Struts vs Coilovers
What Are Shocks?
A shock absorber is a cylinder filled with oil that is designed to dampen oscillations from the coil spring. The coil spring is an integral part of the suspension system. Not only does the spring hold up the vehicle, it also cushions the passengers from large bumps and imperfections in the road.
As the coil spring compresses and rebounds, the oil inside the shock is pushed through small internal holes. The fluid dynamics of the shock absorber dampen spring oscillations. Shocks are not structural components of the suspension and do not hold up the weight of the vehicle.
What Are Struts?
Struts are structural suspension components made of a coil spring and a shock absorber. Struts do support the weight of a vehicle and help keep the wheels aligned. A MacPherson strut suspension is one of the most common applications for a strut.
In a MacPherson suspension system, the strut replaces the upper control arm and ball joint that you would typically see on a double wishbone suspension. The strut top hat pivots as you steer the vehicle.
A strut assembly includes the strut base, the shock absorber, the coil spring, and a top hat to hold the assembly together. Your vehicle will usually need an alignment after replacing the struts.
What Are Coilovers?
Coilover or coil-over is a shortened version of “coil over shock absorber”. Typically, the word “coilover” refers to adjustable suspension components where the shock runs through the spring, as it would on a strut. Coilovers are often found on double wishbone suspension systems, but the term is sometimes used to describe struts as well.
Although non-adjustable coilovers exist, spring and shock assemblies labeled as coilovers are typically adjustable. Adjustable coilovers allow a driver to lower the vehicle, adjust the shock’s compression and rebound firmness, and corner balance the car.
A corner balance is a special type of alignment that allows you to evenly distribute the weight of the vehicle across all four corners. This is done by making small adjustments to each individual spring height while the car rests on scales.
Does My Vehicle Have Shocks or Struts?
Nearly all vehicles have shocks, but sometimes those shocks are part of the strut assembly. If you look under your wheel arches, it is often easy to tell if you have struts or shocks.
Many trucks and front wheel drive vehicles do not use struts in the rear. Multi-link rear suspension systems, torsion beams, and leaf springs will have a shock next to the spring, not inside of it.
Keep in mind that the suspension could look different on the front of the vehicle than it does in the rear. Many economy cars use MacPherson strut suspension on the front axle because it comes with many advantages. MacPherson struts save space, weight, cost, and design complexity.
Vehicles with double wishbone suspension systems typically use coilovers on both the front and rear axles. Although the spring rates and shock length are likely different, the suspension setup should look pretty similar from front to back.
When Do Shocks or Struts Need Replacement?
Coil springs typically last the life of the vehicle unless you live in an area with significant rust. Shocks do wear out after 60,000-110,000 miles, but there are some simple ways to know if you need new shocks.
When you feel excessive bouncing or vibration (particularly at high speeds), your shocks may be worn out. If your shocks or struts have fluid leaking from them, they should be replaced.
While taking a corner over a bump, does the bump upset the vehicle where you feel like you might lose control? This is another sign that you need replacement shocks.
While you’re in there, check the suspension bushings. Worn suspension bushings can cause excessive play in the steering and can make the vehicle much harder to control.
Strut, shock, and coilover are terms that are commonly used interchangeably, but they do not mean the same thing. Differences in suspension architecture from vehicle to vehicle mean the parts themselves are not always interchangeable.
As long as you give the correct year, make and model for your vehicle, you should be able to find the correct replacement part no matter which term is used to describe that part of the suspension.