What Are Coilovers? The Ultimate Guide

Syed Ahmed Ali
10/25/202225th October, 2022
Filed under Beginner Guides

Coilovers provide many benefits for anyone that wants to make the most of their tuned car. We explain everything you need to know about coilovers in this guide.

what are coilovers

Introduction

Coilovers are coiled springs over shock absorbers. Coilovers are one of the first upgrades you should consider because they make a massive difference in performance while providing that awesome slammed look to your ride.

Best of all, they’re not hugely expensive and super easy to fit with a simple toolkit.

coilover front rear 3d render what are coilovers

We’ll discuss everything you need to know about the benefits of coilovers in detail, going over anything you might be wondering about when considering replacing your stock suspension.

Whether you’re interested in what coilovers are, how they work, or whether they’re right for you, we’ll cover it in this guide.

What Do Coilovers Do?

A coilover usually allows you to adjust the preload of the spring, which changes the ride height. Think about it as a tuning factor that you get from installing coilovers.

Coilovers are one accessible unit essential on a race car where you’re constantly adjusting your vehicle setup.

On a track day, you might want to carry out ride height adjustments which are different from when you’re daily driving on local roads. You simply reach for your C-spanner, adjust the coilover, and you’re good to go.

With some coilover kits, you can change broken coilover components if such a situation arises.

At Drifted, we believe in performance, and popular modifications such as lowering and eliminating body roll with adjustable coilovers will undoubtedly transform your ride.

Swapping stock struts for sturdier, stronger coilovers is the way to go when you’re putting high loads on your suspension while drifting or pushing your car hard on the streets or the racetrack.

Are you considering other upgrades alongside coilovers? Then, why not check out our comprehensive guide to modding your vehicle?

How Coilovers Work

To understand this better, let’s dive into the mechanics of a single coilover - we’ll focus on the front coilovers that are based on a MacPherson strut style.

However, aftermarket coilovers have the same principle regardless of your car’s suspension style.

kw suspensions front rear what are coilovers

Strut-type coilovers are mounted between the body and the steering knuckle.

The steering knuckle is connected to the lower arm, and the entire system is designed to resist sway while limiting movement only in the vertical direction.

The steering knuckle is designed so that the steering rack assembly can turn the wheel within the limited range.

The coil over strut assembly comprises a shock absorber, a main coil-over spring, a top strut mount, a helper spring, and a dust boot over the piston rod to prevent contamination of the oil seals.

Despite popular belief, the coil-over takes the weight of the vehicle, not the shock absorber.

The strut housing includes a piston rod, which moves up and down, a rebound stopper, a piston valve unit, a base valve unit, and the hydraulic fluid.

The shock absorber is designed to have working and reserve chambers. The base compression valve controls the hydraulic fluid transfer between these chambers.

Such a configuration using two chambers is known as a twin-tube shock absorber. However, other variants, such as the mono-tube shock absorber, which uses a single chamber are also present in the industry.

coilover strut internal 3d render what are coilovers

Sometimes, coilovers may also have an external reservoir here, which keeps the rebound more consistent and gives it a little more consistency in the temperature of the fluid.

For the traditional shocks to provide optimum performance, the working chamber must be full of fluid.

The purpose of the reserve chamber is to ensure that the working chamber is filled with fluid regardless of how compressed the piston is. Thus the reserve chamber will always be partially filled.

For more expensive coilover sets, the system is added with liquid nitrogen while manufacturing, which expands and acts as a compressed gas on the remaining volume of the reserve chamber.

The calibrated valve at the base controls the resistance experienced by the piston during the compression phase, while the fluid flows almost freely from base to top through the piston valve.

As the piston moves towards the base, the compression valve now opens in a controlled manner allowing the excess fluid to flow to the reserve chamber.

During the rebound phase, the piston rod tries to restore its position against the compressive energy, and the rebound valve ensures this happens in a controlled manner. As a result, the previously displaced fluid to the reserve chamber is pulled back to the working chamber.

The repeating action absorbs the energy from the cars suspension system and transfers this heat to the atmosphere through conduction and convection.

Coilovers may also have helper springs from top-of-the-line manufacturers. The helper spring is handy if the main spring is stiff because if a car hits a bump, the entire length of the coilover shocks may compress.

On the upstroke, the shock will want to oscillate upward, and if there’s not enough mechanical movement left to go upward, it would trigger a violet response and lift the wheel off the ground.

So a helper spring is technically just a placeholder; if you remove it, the mainspring will jiggle around. Again not all coilovers have this; only those that offer more flexibility and a more aggressive lowering amount.

If you’re interested in gaining even more in-depth coilover knowledge, we highly recommend checking out this video:

Opting For A Coilover Upgrade

When it comes to a car’s performance, people usually think of horsepower or the cubic capacity of an engine. But all the power delivered to the power train could be wasted if not handled by an efficient suspension system.

A coilover upgrade will not just provide better ride comfort but also ensures consistent traction to the road surface, better steering stability, and improves the vehicle’s handling.

Are you interested to know which cars are ideal for optimal grip? Make sure you check out our best handling cars guide.

Best Coilover Brand – What’s Best For You?

Choosing your ideal coilover kit boils down to 2 things; the number of adjustments and the quality required.

We recommend coilovers from brands that put a lot of effort into designing their coilovers. Brands like KW, BC Racing, FEAL, HKS, and Tien are all good brands.

Of these choices, BC Racing often provides the best value for money, while KW Coilovers are a premium offering, providing the ultimate German quality.

If you own a common drift car, you’ll find that many manufacturers are making coilovers specific to your model.

For example, our 350Z coilovers guide will provide insight into the best and worst coilovers available and their pros and cons.

Decide the number of adjustments you want, whether opting for the stiff, racing-feel coilovers or a softer coilover to ride speed bumps smoother for everyday driving.

The former is not usually the case since OEM struts are already soft. However, you might find some coilovers that can improve the ride height, handling, and ride quality without making the car bouncy.

You should know that shock absorbers usually last tens of thousands of miles, but they get defective over time due to the millions of operation cycles they must endure, depending on the load.

A failing shock absorber is best inspected at the earliest and should be replaced as required for the efficient performance of the suspension system.

How To Install Coilovers

Installing coilovers isn’t tricky, and in our opinion, it’s one of the first mods anyone should do to their project car to try and gain a basic understanding of their purpose.

It’s a low-effort, high-impact way to quickly change your car’s performance and looks in an afternoon, making it the perfect project for any home or DIY mechanic with basic knowledge and essential tools.

Swapping out your coilovers is not super complicated. These are the tools you’re going to need:

  • Socket wrenches
  • Vehicle jack and stands
  • Hammer
  • Coil spring compressor (if needed to remove the existing coil springs)
  • Your new coilovers
  • Anti-seize for a professional finish

These tools will likely be pretty easy to find lying in your garage.

Power tools are unnecessary but will take a few minutes off the installation.

After you’ve raised your car and secured it using axle stands, you’ll need to remove the wheel.

You need to unbolt the bottom of the shock from the control arm and the top of the strut tower.

You might also need to remove other components that get in the way, like the brake housings, lines, strut bracket, and the sway bar.

fitting suspension coilover kit car what are coilovers

Once the stock strunt and spring suspension have been removed, you can install your coilovers just as you uninstalled the previous setup.

Torque them down to the manufacturer’s specifications using a torquing wrench, and put a bit of anti-seize to ensure the winter grime doesn’t cause any rust issues anytime soon.

If you’ve purchased the correct one, this should be pretty breezy, and no fitment issues will be encountered.

Remember, you need to tune your coilovers before installing them, and read on how to do this. We recommend getting a measuring tape and a set of vernier calipers for this one.

When you’re happy, you can refit the wheel, remove the axle stands, and lower the car back to the ground.

Tuning Your Coilover Setup

So, coilovers are inherently supposed to be adjustable. There are two main aspects of a coilover - the shock absorber and the spring, and you can make two significant adjustments to these.

Firstly, you can adjust the ride height

Adjusting the ride height of coilover suspension requires you to be aware of the three main components of the coilovers; the lower casing lock ring, the lower spring seat lock ring, and the lower spring seat. Your coilovers will come with a special spanner wrench to make adjustments. First, loosen the lower casing lock ring by spinning it counterclockwise and placing a mark on the lower spring seat to help identify the number of full rotations so both sides of the car can be adjusted to the same height.

Firstly, loosen the lower spring seat using the spanner provided. Consider the following:

  • Rotating the lock ring counterclockwise means the lower casing slides up and out, increasing your ride height.
  • The lower spring seat needs to be rotated clockwise to lower your car. Again, do this by using the spanner wrench provided.
  • Depending on whether you’re raising or lowering the ride height, spinning the different rings ensures you do not alter the spring preload. Ideally, this is something that you should already adjust before installation. Again, we recommend referring to the coilover manual for this part.
  • Once adjustments have been carried out, tighten the lower casing lock ring. Then, lower the car down and check ride height before re-adjusting if necessary.

Secondly, you can adjust the damping

A lot of coilovers on the market allow for adjustable damping.

We’ve already made clear what damping is, and you might remember the compression and the rebound cycles of the strut, and in theory, there are two types of damping; compression damping and rebound damping.

Since a basic hydraulic phenomenon is at play, you can change the hydraulic resistance by changing the size of the slits through which the fluid passes.

Manufacturers provide a little knob at the top of the coilover, which clicks on each rotation. Some even have individual compression and rebound damping knobs, but most have just one to control the overall hydraulic resistance.

You cannot see the slits being opened and closed. Still, adjusting is pretty easy, and we’d recommend a simple trial and error method while also consulting the manufacturer’s manual.

Coilovers vs Shocks

There are a lot of different options to go when you’re considering a suspension upgrade.

Usually, the OEM car comes with struts, which are not adjustable.

Coilovers are exactly like struts and have the exact same function, except they have retainers and lock rings with a threaded design for height adjustments. Coilovers also have adjustable piston damping and preload adjustment and are typically stiffer than OEM struts.

But if all you want to do is lower your car, lowering springs might just be what you’re looking for. These days, a good set of lowering springs can be the best option, especially for some fancy kits with electronic damping control.

However, there is a time and a place for lowering springs, and you should always consider important things like the spring type and spring constant.

We recommend you check out our in-depth guide to see how lowering springs compare to coilovers. Oh, and NEVER chop your springs (even if your buddies tell you otherwise) since changing the spring’s length will alter its strength and performance and could potentially be dangerous.

Coilovers vs Air Suspension

There are some air suspensions in the market that handle pretty well. Air suspension works in a pressurized closed loop system, with a compressor pumping air into a sealed boot fixed on a strut which replaces the coiled spring.

So, instead of the springs bearing the load, the air pockets will have the car resting on them. One significant upside is that these systems are electronically controllable, meaning you could alter the pressure in the boots, to change ride height and stiffness.

strut airbag air suspension vs coilover what are coilovers

Air suspension, in our opinion, is never going to be quite as good as a good coilover, simply because they have a habit of developing leaks and are also far more expensive.

Although we’re seeing pro drifters testing them these days, we still feel that the technology has a long way to go to match the trusty coilover when it comes to performance.

In our opinion, you’re best off with some of the awesome value-for-money branded coilovers that we’ve mentioned throughout this guide.

Thank you for reading our ‘What Are Coilovers’ guide.

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author avatar Written by Syed Ahmed Ali Ahmed is an engineer with a major in materials science. He is a true motorhead at heart and loves writing, especially about engines and vehicular dynamics.

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