Many people have coilovers mounted on their cars to enhance handling and efficiency, but they are not set up correctly, and as a result, they may have a variety of handling issues.
How to Install Coilovers On Your Car
Incorrect coilover setup is caused by a large amount of misinformation in the industry, which is exacerbated by the fact that various coilover manufacturers often suggest incorrect coilover setup techniques.
This article explains how to set up a coilover with two points of ride height adjustment and a single point of ride height adjustment correctly.
As seen in the picture below, coilovers with two points of adjustment have damper body height adjustment and spring base height adjustment.
Only the spring base height can be adjusted on dampers with a single point of adjustment.
The damper can be set up correctly using either tool.
A damper with two points of height adjustment allows you to fine tune the bump to droop ratio of the damper stroke on your ride, making it a better option for fine tuning your track car's handling.
The consequences of pre-load must be addressed before discussing how to set the damper's ride height.
Pre-load is another place where there is a lot of misinformation, and it normally does not exist as many people believe.
Since most cars use a linear rate coil spring, the spring rate does not change when the spring is compressed.
As a result, if you compress a linear coil spring at a rate of 10kg/mm by applying 100kg of mass to it, the spring's rate would remain 10kg/mm and the spring will compress by 10mm.
If you add another 100kg to the spring for a total of 200kg, it can compress by another 10mm, and so on.
In the diagram above, the distinction between the first and third springs is that spring 3 now has accumulated energy and the desire to expand.
When you put the mass of your car on spring one, however, it will also hold a comparable amount of stored energy, essentially making the "preload" redundant.
If you compress the spring to the point that the coils begin to bind at maximum droop, the spring rate will be affected by the inactive coils, which will change the spring rate.
In this scenario, you can either mount shorter springs with the same spring rate or remove any helper springs that are present.
Only in the case of a variable rate coil spring does pre-load occur.
This is a spring that has different spring rates in different parts and adjusts spring rate as the spring compresses.
This type of spring is much more uncommon, and the amount of compression at ride height affects the spring rate at each corner.
However, linear rate springs are used in the vast majority of applications, including motorsport.
Setting Damper Travel
When setting up the damper on the car, make sure there is enough bump and droop travel in the damper once the car is sat at ride height to optimise output.
For most vehicles, the damper should be adjusted such that 2/3rds of the available travel is for bump and 1/3rd of the available travel is for droop while at ride height.
To do so, detach the damper's spring and measure the length of the damper shaft that protrudes from the damper body when completely extended.
After that, completely compress the damper and calculate the length of the protruding damper shaft.
use the below equation to calculate the total amount of damper travel available:
With damper travel calculated you can now calculate the amount of droop travel for your damper:
With your droop travel calculated you can now calculate bump travel for your damper using:
Place the damper onto the car correctly while the spring is still away from the coilover.
If you race your car in a championship, the laws and regulations are likely to include front and rear ride height restrictions.
If this is the case, use jacks, axle stands, or wood to raise your chassis to the minimum ride heights required front and rear before installing the wheels.
To set the bump to droop ratio measured above, change the damper using the damper body height adjustment.
We've highlighted the damper rod in the animation below to illustrate the droop travel (red) and bump travel (green) that we want from our damper.
Setting the top of the damper body on the line between the red and green zones with the damper body adjustment would ensure that we have the right amount of bump and droop travel available from the damper.
Then, jack up the wheel all the way until the bump stop is engaged, thus keeping the wheel in place.
Hopefully, your wheel will not come into contact with your bodywork or your wheel arch at this stage.
If it does not make contact, proceed to the next section to mount your spring and fine-tune the ride height.
If your wheel does get in the way, you'll have to make some choices.
One option is to increase your car's ride height by the amount of damper travel remaining until the bump stop engages.
If you're in a situation where you're just driving too slowly, this is a good idea to consider.
If you've set your car to meet a championship's ride height specifications, you can cut away the inner arch or fit wider bodywork to avoid interference and allow the wheel to recess into the bodywork.
If the tyre is making contact with the outer wheel arch, check the camber settings as well. If you haven't aligned the car yet, you might have it set to positive camber or not enough negative camber at ride height, which may be causing the interference.
If none of the above scenarios apply, you will need to use the lower damper height adjustment to remove any of the bump travel.
This is a last resort because it would reduce the amount of bump travel while increasing the amount of droop travel, causing the ratio to be thrown off.
Setting The Ride Height
You can now remove the coilover and reinstall your coil spring on your damper after setting the bump and droop range correctly on the damper.
After reinstalling the full coilover, you can now lower your car to the ground and sit on the floor.
Since the car's mass is now sat on the spring and damper, the ride height would almost certainly be different than it was before due to the spring compressing.
This is totally understandable.
The lower spring platform can now be used to adjust the car's ride height.
Turning the lower spring platform upwards raises the car's ride height, while turning the lower spring platform downwards lowers the car's ride height.
The aim is to use the lower spring platform to raise or lower the spring's base until you reach the ride height you desired based on regulations, experience, measurements, or data.
Don't worry if you compress the spring in the process; it won't hurt much.
Only if you compress the spring to the point that the coils bind and become inactive should you be concerned.
Install a shorter spring with the same stiffness in this situation.
After you've adjusted the ride height, jack up the car and raise the wheel off the floor so that the damper is completely drooped.
Check that the spring is still captive between the upper and lower mounts at this point.
If it is, then the lower spring perch collars should be locked off since the damper is now properly mounted.
If the main spring is loose, you'll need to mount a helper spring to hold it captive under maximum droop.
If you need to add a helper spring, you'll need to lower the spring perch by the same amount as the helper spring's compressed thickness.
Re-check the ride height after it's been mounted and modified, as the spring platform can need to be tweaked further.
With this final modification completed, your coilover is now properly set up and ready to use.
Many people have been taught a completely different way to set up a damper.
This is due to a great deal of misinformation surrounding the topic, some of which also comes from the coilover manufacturer and is recommended on the documents that come with the coilovers.
However, despite the high quality of the product, it is effectively a copy of another product on the market, and the background information that should have been present on the manufacturing line when producing these items and offering fitting manuals, etc. was not present.
This isn't to say that the goods aren't of good quality.
When looking at brands like KW or AST, you'll notice that they often market coilovers with only the spring platform adjustment and no damper body ride height adjustment.
This is because they design an optimal ride height for the damper's intended use, essentially pre-setting the car's bump and droop ratio and pre-determined ride height.
The spring platform can then be used to customise the ride height to your preferences.
The damper body adjustment is also included with Ohlins coilovers as an added bonus, allowing you to fine-tune the bump and droop ratio of the damper for your specific setup.
Consider the following scenario: you have a 26Kg spring mounted on your coilover and you are now switching to an 8Kg spring with the very same unsprung duration.
This is an extreme case, but it illustrates the point.
If you used the lower spring platform to increase the ride height, once the softer spring was attached, you would have raised the car and pulled the damper piston up within the damper frame, restoring the bump travel to where it should be.
This way, you've accomplished the ride height adjustment while also restoring the damper ratio to its proper setting.
Handy Video On Installing Coilovers
Please leave a comment below if this coilover guide has helped you change your car by installing coilovers.