Recently, we’ve found ourselves writing more and more suspension upgrade guides. Coilovers are a major topic as they’re a popular choice when upgrading. However, there’s almost too much to cover in one single article. It’s a lengthy topic that can often be confusing and overwhelming. What are coilovers? How do they differ from struts and shocks? What are springs, lowering springs, and spring rates? What about twin-tube vs monotube suspension, damping adjustments, and more?
Again, it’s a lot to discuss and may sound overwhelming at first. Worry not, though. In this guide, we answer all of these questions and more as we explore the ins and outs of coilovers, struts, shocks, and springs.
What Are Coilovers?
In this article, we do our best to start from the basics and work into the more in-depth topics. At the end, we’ll also discuss some of the best and most popular coilover kits around. So, looking at the very basics – what are coilovers?
The term coilover comes from coil-over spring. It’s simply a type of suspension that allows adjustments to ride height, camber, damping, and more. To best understand what coilovers are, let’s jump in and discuss the differences between traditional shocks and struts.
Shocks vs Struts vs Coilovers
It’s not always easy to explain perfectly in words. As such, check out the above video for a good starting point in understanding shocks, struts, and coils. We really like the above video as it’s concise and easy to understand. To expand a bit further let’s summarize the main points.
All of these suspension components center around the shock absorber (shock for short). A shock is a hydraulic pump that uses fluid and/or gas to help dampen impact and rebound movements. This is what helps maintain a smooth ride while keeping the tires planted to the road.
Then you have struts. A strut is a shock absorber with the addition of a coil spring collar. The coil springs are then mounted on the shock, so the spring wraps about the shock absorber. Some refer to struts as coilovers, which isn’t totally incorrect.
A coilover is essentially a strut, but there’s one major difference. The shock body is threaded or has multiple grooves. This allows the coil spring collar to move up and down on the shock, effectively changing the vehicle’s ride height. In other words, a coilover is like a strut except it allows for adjustable ride height.
Adjustable camber and damping are two other aspects commonly found in coilovers. More on those topics later. For now, let’s tie this together further by discussing the coil springs.
What Are Coil Springs?
Coil springs came up several times in the last section since they’re an important aspect of struts and coilovers. With a shock absorber, the vehicle still uses a coil spring, but it’s mounted separately. On the other hand, the coil spring mounts on the shock absorber when referring to struts or coilovers.
Anyways, coil springs are possibly the single most important part of a suspension setup. It’s the springs that actually hold the entire weight of the car – not the shocks. Coil springs help support the vehicle’s ride height, maintain proper alignment, and absorb shocks and impacts. Springs also control body roll while cornering, accelerating, and braking.
The springs actually absorb more impact than shocks since they hold the vehicle’s weight. Shocks essentially help bring the springs back to their natural position. If shocks weren’t on the vehicle then the coil springs would continue bouncing, so it’s the shock that dampens those movements. Springs are a topic we will cover in more depth shortly.
What Do Coilovers Do?
Coilovers act exactly like any other suspension setup. They help dampen impacts, hold the vehicle’s weight, keep the tires in contact with the road, control body roll, and more. It’s the same stuff that any car’s suspension does whether it’s a shock, strut, or coilover.
What makes coilovers so special, then? Again, it mostly comes down to the adjustable ride height. Damping and other adjustments are common with coilovers, but traditional shocks or struts can also offer these features.
Benefits of Coilover Kits
With some of the basics out of the way let’s discuss the benefits of coilover upgrades. There’s a lot of flexibility and possibilities with coilovers. It doesn’t just have to be about lowering or all-out handling. Some benefits of coilover kits include:
- Adjustable ride height
- Adjustable damping
- Improve handling, braking, accelerating
- Better comfort & ride quality
- Replace old, worn suspension
It’s unlikely you’ll get all of these benefits from one single set of coilovers. Often, aggressive setups intended for track use and handling are stiffer. This will sacrifice some ride quality and comfort, but it doesn’t have to be much. That’s especially true with a good setup and adjustable coilovers.
They’re also a good upgrade for lowering, which helps the center of gravity. Some prefer coilovers for stance and slamming their car all the way to the ground. Others just want a modest setup that functions well for everyday street handling. Point is – there are lots of different options.
Another big one is simply replacing old suspension. Shocks and coil springs are wear-and-tear parts that often require replacement as they age. If you’re on old suspension and can upgrade to coilovers for the right price then why not?
Whatever your interest in coilovers it’s important to understand your goals and budget. Different goals and uses often necessitate different coilover kits for the best results. As such, in the rest of the article, we’ll move onto more in-depth topics about what to look for in coilovers upgrades.
Coilovers vs Lowering Springs
Many choose to upgrade coilovers to lower their car. However, lowering springs are another common option if you’re simply looking to drop ride height. Going with springs only is the cheapest option. There are some big downsides when opting for lowering springs, though. These can include:
- Non-adjustable ride height
- Faster shock wear
With lowering springs you choose the springs that obtain your desired height. However, if you want to raise or lower the car further you’ll need an entire new set of springs. You can’t simply adjust within minutes as with coilovers. Springs alone can also increase shock wear, which means you may need new shocks anyway.
Ultimately, we think coilovers are the much better choice. That’s especially true since lowering springs won’t usually provide drastic improvements to handling (without also addressing shocks). You can find some very well-priced coilovers if you’re not too concerned with handling and just want to lower or stance your car.
What Are Spring Rates?
Spring rate is one of the most important topics when it comes to coilovers or lowering springs. Spring rates are stated in two primary ways:
- kg/mm (or K for short)
For example, a spring might have a rate of 400 lbs/in. This means it requires 400 pounds of force to compress the spring 1″, 800 pounds to compress it 2″, and so on. Kg/mm is standard for the metric system and 1kg/mm equals roughly 56 lbs/in. As such, a 400-pound spring equates to 7.15 kg/mm or 7.15K. It’s common to see them referred to simply as K.
When spring rates are stated in this manner it’s consistent with a linear spring. Progressive springs are another popular coil spring design, though.
Progressive vs Linear Spring Rates
A progressive coil spring has varying spring rates. Notice the spring on the right of this image is linear. Due to the linear design the spring rate is always the same – as we discussed in the previous section.
On the other hand, the spring on the left of the image is a progressive rate spring. It will have different spring rates depending on how far it’s compressed. The general idea is to have a softer spring rate for everyday street use, but it stiffens up under higher compression.
If you’re looking for a modest setup or stance then there’s nothing wrong with a progressive spring. They can deliver a good overall balance. However, progressive rate coils can be hard to match with the right shocks. They’re also not ideal for handling, so those looking for improved handling should consider linear rate coil springs.
The Importance of Spring Rates
There isn’t a perfect answer as to the best spring rates for each vehicle or setup. At least not without extensive testing that the general public likely doesn’t have the time or money for. It’s usually best to let the spring or coilover manufacturer choose the correct spring rates. Some also give multiple spring rate options and can help you choose the best rates for whatever your goals and needs.
Anyway, there are a few general rules to follow here. A higher spring rate means a stiffer spring. Stiffer springs help minimize body roll and weight transfer, which is generally good for handling. That does NOT mean stiffer is always better, though. Stiff springs are great on smooth surfaces, like a racetrack. On public roads with bumps and imperfections going too stiff can actually make handling worse.
Otherwise, if you’re looking to lower your car a lot you will need stiffer springs. This will help prevent the shocks from bottoming out on the bump stops, and the car from bottoming out in general.
What To Look For In Suspension Upgrades
Alright – with springs out of the way let’s re-focus on the shocks. This is where coilovers offer lots of potential adjustability. One important topic to cover before adjustments is the shock design itself.
Twin-Tube vs Monotube Shocks
Remember, the shock is essentially a hydraulic pump that uses gas and/or fluid to dampen compression and rebound. A twin-tube shock has two cylinders. One is the main cylinder – known as the inner or working cylinder – which contains the piston. The other cylinder is a reservoir for the hydraulic fluid or gas.
Monotube shock designs have one single cylinder. There’s an area for fluid and another for gas, and the piston moves within the fluid portion. We could spend a while breaking down how both of these shocks work, but that could be an article of its own.
Instead, let’s focus on how they actually differ in comfort and performance. Monotube shocks will offer the best response, damping, and ride quality. They’re more expensive than twin-tube shocks, which is why not everyone goes with monotube. Twin-tube shocks can still be a great choice, but if you value handling the most then you’ll want to consider monotube options.
Coilovers Damping Adjustments
Now, there are three main types of adjustability you might find on shocks. Manufacturer pre-set, single, or double adjustable. The pre-set doesn’t allow for any actual adjustments. Instead, you have to trust to coilovers manufacturer to set the proper compression and rebound damping. Most will usually target a blend of performance and street comfort.
However, if you want the ultimate handling and street setup then adjustable is the way to go. This allows you to stiffen the shocks for track use or aggressive driving. In a matter of minutes, you can switch back to softer settings for everyday street use. It’s the best of both worlds.
The common options are single and double-adjustable. Single adjustable may only control either compression or rebound damping. It may also control both forms of damping, but you can only adjust them together. Double adjustable allows for independent control over both.
Ride Height Adjustments
Last up is ride height adjustment, and this is a pretty straightforward topic. Keep an eye on different coilovers and what ride height ranges they allow for. Some kits may meet your lowering goals while others will not.
We find most standard coilover kits allow for about 1-2.5″ of height adjustability. It can vary a lot from kit to kit and car to car, though. Some coilovers are also designed more for stance and may allow drops of 3-4+”. When it comes to high-end performance coilovers for handling and track use the lowering ranges are usually less drastic. They may only offer a lowering of about 0.5-2″.
Best Coilovers Upgrade Kits
Not to stray off topic, but we must admit we went a bit further than intended on the above topics. Even then, there’s a lot of specific info and technical detail we skipped over. In the future, we’ll likely break down these topics in greater depth if there’s any interest.
For now, let’s move onto some of the best coilovers around. Keep in mind – this is far from an exhaustive list and lot’s of great coilovers exist. We’re sticking to a few of our favorites for different budgets and goals that are available for a large number of makes and models.
1) Raceland Coilover Kits
Tier: Entry-Mid Level Street & Stance
Adjustable: Mostly No (a few kits are adjustable)
Raceland is a bit of a controversial company. Some immediately assume they’re not quality coilovers since they’re so well priced. However, many customers are incredibly happy with their experiences on Raceland coilovers. To be clear – these are entry-level street and stance coilovers. They’re not going to be the best handling or comfort options around. Raceland products do exactly what they’re meant to do, though.
They are quality, entry-level coilovers at a nearly unbeatable price. Raceland offers great customer support, and has very low return rates due to the great quality and service. Realistically, that’s about all you can ask for at this price and Raceland absolutely delivers.
Most offerings include their Classis and Ultimo coilover kits that offer 1-3″ and 2-4″ lowering, respectively. They aren’t adjustable and don’t include top-hats, camber plates, or anything of the like. That’s pretty standard for a coilover upgrade in the $400-550 ballpark. However, some makes and models do get monotube, adjustable, and other options for about $600-750.
Ultimately, Raceland is great for a modest upgrade for the streets, lowering or stance, or simply replacing old suspension. If you’re looking for handling over all else then you’ll find better options out there (albeit more expensive options). That’s nothing against Raceland – it’s just not their market. They build quality, entry-level coilovers and they do it very well.
2) BC Racing Coilovers
Tier: Mid-High Level Street, Stance, & Track
Price: ~$1,030 – 3,000+
Another popular coilover option is BC Racing. Most, if not all, of their kits are adjustable and offer insane customization options. They have Extreme Low coilovers, you can choose between their springs or swift springs, choose your own spring rates, etc. The BR-series coilovers are their cheapest option, which start around $1,030. Even these are adjustable and offer front camber plates when applicable, and optional rear camber plates.
You can then work your way up to their top of the line kits, which can come in at $3,000+. They have tons of options in between too. Point is – BC Racing offers tons of coilover kits with great customization. Their BR-series are very popular since they deliver great performance and features for the price.
Not many kits on the market offer as many options and customization as BC Racing. That alone earns them a spot on the list of our favorite coilovers. Top that off with the fact they’re quality coilovers with extensive testing and highly proven results. And they’re very well priced in the market. If it all sounds too good to be true…well, it’s not.
3) KW Coilover Upgrades
Tier: Mid-High Level Street & Track
Adjustable: Yes, some kits
Price: ~$1,000 – 5,000+
Where to even begin with KW. If you’re at all familiar with coilovers you’ve likely heard of KW. They’ve been around since 1992 and offer excellent kits for tons of makes and models. KW coilovers have won all sorts of 24 hour races at the Nürburgring. These guys know what they’re doing and build some awesome top-tier, high performance coilovers.
However, they also offer a lot of street friendly options alongside street & track and track-use kits. Start with their Street Comfort kits which usually begin around the $1,000 to $1,200 price point. Next is the KW V1 which aren’t adjustable. However, these coilovers are highly tested from the factory and set to a great balance of comfort and performance.
Then there are the KW V3, clubsport, competition, and even more. They have it all ranging from mild to wild, and everyone of them delivers top-tier results in their class. Yes, you are paying a premium for their brand name and image and high quality, proven results. However, if you’re looking for some truly excellent coilovers then KW delivers everything and then some.
Internal Coilover Resources
If you’re looking for more info on coilovers for a specific car or model then be sure to check out our other guides. We have coilover upgrade guides for tons of different cars including the below list:
- Honda Civic Coilover Upgrade Guide
- Mazda Miata NA Coilover Guide
- Mazda Miata NB Coilover Guide
- Mazda3 & Mazda Speed3 Coilovers
- Hyundai Genesis Coupe Coilover Guide
- Infiniti G35 Coilovers
- Nissan 350Z Coilover Guide
- Lancer Evo X Coilover Upgrades
- Mazda RX-8 Coilover Guide
- Subaru WRX Coilovers
- Subaru BRZ, FRS, and GT86
- Scion xB Coilover Guide
- Scion tC Coilovers
Please let us know in the comments below if there are any other models you’d like to see coilover guides for.