Aside from tires, your suspension setup is one of the most important elements that’ll affect your handling, comfort and ability to set some decent lap times on the track. It also plays a massive part in improving your cars visual appearance too.
When you’re looking for coilover suspension, there’s plenty of options on the market. You’ll want to spend a bit of time researching manufacturers that are well established and respected, Öhlins, Tein and Yellow Speed Racing, for example.
A coilover essentially replaces the entire factory spring and shock assembly for an all in one full bodied coilover often referred to as a ‘true coilover’, or in some cases, a separate rear spring and shock. Although there’s no superior type of coilover, many people feel that the ‘true coilover’ is a better choice, partially because the location of the spring has moved from its factory position which then changes the motion ratio and can help to optimise handling
The right coilovers
It goes without saying that you wouldn’t wear a pair of formal shoes to play football in, likewise, you wouldn’t wear a pair of football boots to play ice hockey in. These are the same principles when it comes to choosing the right coilover setup for your car.
If you’re only going to use your car on track, then you’ll want some stiffer coilovers that have plenty of adjustment. However, if you’ve got a car that’s being built for stance and not being used on the track, chances are a set of coilovers that are comfortable and have a good range of lowering adjustability will be more than adequate.
Generally, the higher the budget, the more damper adjustability you’ll get which are perfect if you’re looking to shave those last few tenths of a second off your lap times but not necessarily important if you’re putting them on your daily driver. It’s important that you research what coilovers you’re investing into and that you’re not just opting for the most expensive because they look the nicest.
Springs and shocks
So, let’s take a look at the different components of a coilover, the springs and shocks. These work in perfect harmony together, and if they don’t, you’ll start to experience bad performance from your suspension.
The springs are what keep your chassis from bottoming out and control your tires when going over bumps. They also reduce body roll, squatting under acceleration and the front of your car nose diving when you hit the brakes.
When it comes to springs, you’ve probably heard of spring rates too. Basically, a springs rate is the amount of weight required to compress itself per millimetre. It’ll look something like this 6kg/mm. The bigger the number, the stiffer the spring. It’s important to stress that a higher spring rate doesn’t mean better performance, if they’re too stiff then ride quality will suffer, and your tires won’t be able to grip on bumpy surfaces. If they’re too stiff, you run the risk of making your car handle a whole lot worse than the factory setup. On the other hand, if your spring rate is too soft, then you’ll find that your chassis will bottom out. Spring rates are a personal preference based on how comfy you want the car to be versus how well you want the car to perform on track. Road cars will ideally want a lower spring rate to soak up the bumps, whereas a race car would benefit from a stiffer spring rate to maximise contact with the track.
The shocks control and dissipate the energy created from the springs by converting it to heat energy. This heat is then cooled down by the internal fluid that passes through small holes in the head of the piston. If you didn’t have shocks, the energy from the spring would continue to compress and decompress repeatedly until the energy diffuses.
There are a few different types of top mounts on coilovers, rubber, pillow-ball or coilovers that simply use the OEM top mounts. You’ll find that some models of coilovers have adjustable top mounts to change things like camber and caster, which is especially useful when it comes to dialling your car in correctly.
Most coilovers will use a pillow-ball top mount, which is a spherical bearing that is used as the joint between the strut assembly and the top-hat, where it mounts to the car. A pillow-ball will produce sharper and more precise handling, but at the sake of a harsher ride and increased vibration.
Some of the newer brands on the market offer rubber top mounts. Whilst they’ll be stiffer than the OEM setup, a coilover that uses rubber mounts will be much more forgiving for a daily driver.
Some coilovers, do away with the inclusion of top mounts and instead use the top mounts that your OEM suspensions uses. These will offer the most comfortable ride quality but won’t necessarily increase performance.
Preload/Compression and Rebound
Preload is the pressure that’s applied to the spring based from how far they are compressed. By adding preload, you can help to increase your cars traction, however, excessive preload will have a negative effect. You’ll find that cheap coilovers will change the cars ride height when preload is applied, which goes without saying, isn’t very good! The majority of coilovers don’t run any preload, instead the correct springs should be chosen to achieve the desired spring rate.
Compression happens when the shocks piston moves into its body, compressing the fluid in its chamber below. Rebound happens when it’s pulled away, again, compressing the fluid. Simply put, compression controls how fast weight is applied towards the wheels and rebound controls how fast the weight moves away. Almost all coilovers on the market will come with an adjuster to change the compression. However, you’ll find that the more high-end coilover will have 2, 3 and sometimes even 4-way adjusters to allow for finer tuning of compression and rebound settings, including settings for high and low speeds.
Adjusting the height of your coilovers
When it comes to installing your coilovers and setting the ride height of your car, you’ll want to start by getting your measuring tape. Ideally, you want to try and get all 4 corners at the same height. Simply measure the distance of the exposed threads left on the coilover rather than measuring the arch gap when the car is back on the ground.
After you’ve installed the coilovers, set the car back down onto the ground, allowing time for the suspension to settle so you can see where it now sits. If you need to make further adjustments to the ride height, simply jack the car back up and adjust the collars on the lower mount to increase or lower the coilovers. Make sure to keep a note on each corner for the measurement so you can try and match them all up. Simply repeat these steps as many times as needed until you’ve got your desired ride height.
There’s a couple of pointers that are worth paying attention to as well when it comes to setting ride height.
Even if your measurements are all perfectly matched, it’s possible that you might have to raise or lower one side more than the other. Every vehicle is different and isn’t always perfectly weighted 50/50 from side to side.
Now would be the perfect time to get a coat of ACF-50 or put a set of coilover sock covers on to stop them from getting seized and taking a beating when they get exposed to the elements.
If you do measure the arch gap when the car is on the ground, don’t measure from the ground to the arch. There are plenty of variables that come into account if you do this so measure from the top of your rim or middle of the centre cap for more accuracy.
If you’re looking to optimise your setup for grip, rake can help to adjust the balance of the car. By raising the rear ride height, this can be a quick fix to reducing grip at the rear of a front wheel drive car.