Coilovers: Tech, Buyer Guide & Brand List

Hi everyone!

This is a guide for newcomers and others with little understanding of coilovers.

Suspension is a fundamental way of improving the looks and/or performance of your car. Although coilovers are usually seen as an instant suspension mod, incorrect selection can lead to disappointment. To help members understand and find the right one for them, this thread will go through coilover basics, technical details, buyer guide and a list of brands.


Disclaimer: This is a basic guide that presents information in its simplest form possible and therefore may NOT be entirely accurate.


Coilovers: Basics


Coilover Definition

So what exactly are coilovers?

Coilovers in our context refer to a threaded shock absorber with matching springs. This means that even the most basic coilovers are free height adjustable within the allowed threaded body. They are not to be confused with coil-over which is a suspension layout (Macpherson).


Coilover Features

Let's go over what a basic coilover looks like and its typical features.

Here is a picture of a typical basic coilover:

http://www.jscspeed.com/part_pictures/cusco_z1_evo.jpg

Credits - Cusco/JSCspeed

Features:

• Pillowball Upper Mount - Most coilovers don't reuse the top hat of the stock shock absorber. Unlike the rubber top, the solid pillowball upper mount doesn't distort under force so the driver has more consistent driving feel at the cost of comfort; with metal on metal, it is not unusual to hear the tops banging when the car is going over rough road.
  
  For cars with Macpherson strut, special pillowball upper mounts can be integrated with adjustable camber plate to allow camber adjustment.
  
  N.B. The 'bearing' inside these tops also tend to wear out faster than the rubber top mount. So when you start hearing squeaks, a good place to start is the top mount and not the rest of the coilover.
  
  
• Lower Spring Seat - Basically where the spring is seated. On traditional/partial threaded coilovers, this is also used to determine ride height.
  
• Threaded Section [Screw adjustment section in picture] - This is where the lower spring seat and lock nut are screwed in to allow height adjustment.
  
• Lock Nut - Used for height adjustment on fully threaded coilovers.
  
• Lower Mounting Bracket - This bracket secures the coilovers to the suspension actuator(s).

Coilovers: Advanced

Now that you know some coilover basics, let's check out the more varied features that coilovers can come with and the science behind them.

Coilover Features

• Damper Type - There are two types of dampers:
  
  http://www.tein.co.jp/e/special/ni_t.../img_tigai.gif
  Credits - Tein
  
  
  
  • Twin-tube - Hydraulic & Low Pressure Gas - [LHS of Pic]
    
    
    • Construct - Twin-tube refers to a shock absorber that contains two cylinders: inner and outer. The piston valve that displaces the fluid is located in the inner cylinder.
      
      
    • Advantages
      
      • Suspension Stroke - Twin-tube stroke length is along the entire body of the shock absorber, whilst the monotube's is shorter because the oil and gas chambers are stacked on top of each other.
        
      • Comfort [Due to gas] - Using low pressure gas allows twin-tubes to absorb shock better, resulting in greater comfort.
        
      • Durability [Due to gas] - Low pressure gas also means less pressure is forced against the seal so there is less friction, which allows it to last longer.
        
      • Cost - Twin-tubes are invariably cheaper to make than monotubes because of their components, design and manufacturing process
      
      
    • Disadvantages
      
      • Lack of fluid capacity - As the twin chambers take up more space inside the shell casing, twin-tubes contain less fluid than monotubes, reducing their ability to maintain consistent performance for long durations.
        
      • No Precision Dampening [Due to gas] - The twin chamber design means a smaller piston is required; therefore a twin-tube typically can not provide as precise dampening as a monotube.
        
      • Aeration [Due to gas] - The entire unit is under high stress because both the fluid and gas chambers are not separated. The combination of the rapidly moving piston, fluid and valve creates friction. If the fluid is forced through the value at a sufficiently high speed, this forms air bubbles in the fluid behind the piston, which is called aeration. This can lead to foaming that results in the shock absorber not dampening properly.
      
      
    • Suitable Application - Street (and Track for high quality twin-tubes)
    
    
  • Monotube/Inverted Monotube - [RHS of Pic]
    
    
    • Construct - Unlike the twin-tube, all of the shell casing's interior acts as the cylinder.
      
      
    • Advantages
      
      • Consistent level of dampening - The monotube design has a greater fluid capacity, allowing for increased heat dissipation and therefore more consistent performance.
      • Precision Dampening - Monotubes can run a larger piston due to their single cylinder design. This allows for a wider distribution of pressure that enhances the shock's precision.
      • No Aeration - Both the fluid and gas are completely separate so there is no aeration to hinder dampening consistency.
      
      
    • Disadvantages
      
      • Lack of Stroke/Bottom Out - As the oil and gas chambers are placed on top of each other, a monotube typically has issues with maintaining sufficient stroke. This makes it more prone to bottoming out.
      • Stiffness [Due to gas] - Monotubes by nature require high pressure gas in the gas chamber. This impairs shock absorption ability, making them comparatively stiffer than twin-tubes.
      • Durability [Due to gas] - As mentioned above, the requiring high pressure gas also leads to accelerated seal wear, thus causing increased internal friction that leads to premature failure.
      • Durability [Due to inverted design] - Unique to inverted monotubes, their complex design and additional moving parts means more things can fail.
      • Damage Resistance - The internals of the shock absorber are placed very close to the shell casing; so if the shell casing is damaged, it will also damage the internals.
      
      
    • Suitable Application - Circuit and Street [High quality coilovers can provide sufficient dampening and stroke]
    
    
  • Threaded Type - There are 2 types:
    
    
    • Traditional/Partially Threaded - Not as common but still found on some basic coilovers. Traditional threaded or partially threaded coilovers have a threaded section which does not run along the entire length of the shock body. This means that when adjusting height, the lower spring seat is adjusted and not the lock nut. The result is this:
      
      http://www.jdm-option.com/eng/pr_CUS.../sus_img10.jpg
      Credits - Cusco/JDM Option
      
      Improper height adjustment will mean that the spring will be loose and therefore lose damper stroke, resulting in the car hitting the bump stops or "bottoming out"; making the car uncomfortable.
      
      
    • Fully Threaded - Fully Threaded Coilovers have thread that runs along the whole length of the shock body. When adjusting the height, the lock nut is adjusted and not the lower spring seat. Damper stroke is retained as the springs remain unchanged and in place. This picture illustrates the height adjustment process:
      
      http://www.jdm-option.com/eng/pr_CUS.../sus_img11.jpg
      Credits - Cusco/JDM Option
      
      Preserving damper stroke minimises the chances of bottoming out and retains comfort.
    
    
    
  • Damper Adjustable - The most basic coilovers are usually non-damper adjustable; they're pre-tuned from the factory. On the other hand, the compression and/or rebound settings of adjustable dampers can be changed using a knob. Simply put, this allows you to adjust the 'damper force' or 'stiffness' of the coilovers. Different types of damper adjustability available are:
    
    
    • One-Way Adjustable Damper - Controls only compression or only rebound or combines compression and rebound. This setup is normally found on low-end coilovers and is the most user-friendly.
      
    • Two-Way Adjustable Damper - Controls compression and rebound independently. Allows for finer tuning of coilovers and is usually found on entry-level competition coilovers.
      
    • Three-Way Adjustable Damper - Controls compression and rebound independently, but one has a high/low speed setting (usually compression). You will find these on professional competition coilovers and the Hi/Lo speed adjustment on the remote/piggyback canister/reservoir.
      
    • Four-Way Adjustable Damper - Controls compression and rebound independently; both have high speed and low speed settings. As above, found on the most expensive coilovers.
    
    
  • Damper Valving - Something that is often disregarded is the damper's valving. A damper's valving is its ability to control compression and rebound during all conditions. It's what makes some setups beautiful on smooth tarmac while being absolutely nerve-racking on the street. A shock absorber with good valving will compress and rebound in a way that gives the driver confidence; it will not behave erratically or harshly when pushed but it will absorb the force to allow the driver to retain control and push on. Different types of damper valving available are:
    
    
    • Linear - Linear, as the name implies, means that the shock absorber's dampening force increases at a linear rate as the piston speed increases. This is the most common valving found on coilovers.
      
    • Progressive - Progressive at low piston speed has softer dampening force but this increases at high piston speed.
      
    • Digressive - Digressive is the opposite of progressive in that it has harder dampening force at low piston speed but decreases at high piston speed. This is generally used in high-end coilovers.
    
    
    N.B. This is purely a comparison of each type at extremes and their general behaviour.
    
    For example, when you ride a bump, a linear valved coilover will react with equal force. A progressive valved coilover will suddenly stiffen while a digressive valved coilover will soften the blow.
    
    
  • Spring Rate - Spring rate is basically how stiff the springs are in the coilovers. You can tell a lot from simply comparing the spring rate of the coilovers to other benchmarks like other coilovers of the same application.
    
    Spring rate is read like this: a 2kg/mm spring means that to make the spring compress 1mm, a load of 2kg needs to be applied. In the context of cars, this example is a very soft spring and usually found on base econoboxes where ride and comfort are key.
    
    Stiffness is not universal however; it is determined by your car's weight, suspension layout and application. The heavier the car is, the higher the spring rate needs to be to counteract its weight. Similarly cars with double-wishbone (Pre-2000 Civics/Integras, Preludes, S2000, Accord Euro, etc.) can run higher spring rates without experiencing the harshness felt by those running Macpherson (Post-2000 Civic/Integras, etc.). Application plays a key part too; in general street cars should run more conservative spring rates than those of track cars to account for unpredictable surfaces and conditions.
    
    
  • Active/Variable Dampers - The latest innovation in suspension technology is the active/variable dampers as seen in some of the latest cars from Ferrari and Nissan, which are slowly becoming available in aftermarket parts. These dampers, as their name suggests, actively alter the dampening to suit driving conditions. They are typically smooth and comfortable but firm when needed.

Coilovers: Buyer's Guide


Where to start?

• What am I after - Make sure you know what you want, be it just a simple drop, a drop and some performance, drop/performance/comfort or whatever combination, otherwise you will end up running something that you will dislike and make the car a pain to drive. Remember that we mod our cars because we want to enjoy them.
  
  
• Application - Similar to the above, application is also everything. After all, there is no point running super stiff circuit valved coilovers on a car that will only see the street and driven mainly on broken tarmac. That's just a recipe for disaster not only in performance, but to your own safety.
  
  
• Budget - Another important point is the amount of money you feel justified to spend. If your budget doesn't allow for the dream setup, you must look for a compromise.

What to look for?

• Damper Type - Twin-tube or monotube? In a perfect world, twin-tube would be used for street and monotube for track. It's not that simple however; a high quality monotube will almost be on par in comfort as that of twin-tubes and will almost last as long. Conversely, a low quality monotube is horrible for street and tends to wear out very quickly, so it will feel like it's not absorbing the bumps at all.
  
  For cars that are used as a daily, a twin-tube or high quality monotube will give you performance and comfort.
  
  For cars that are used on the track more often than the street, a low or high quality twin-tube/monotube coilover is suitable; budget and performance goals will determine which one you would go for.
  
  
• Damper Valving - Digressive is often regarded as the best damper valving and for good reason. They have a good feel at low piston speed whilst giving a softened response at high piston speed speed, minimising harshness and providing control. Digressive coilovers however are some of the most expensive on the market.
  
  Most affordable coilovers for the average owner will have linear or progressive valving, which are set with a stiff bias. This can be intolerable on harsh surfaces and if it's really badly made or set up, it can be painful to ride even under normal driving conditions.
  
  
• Spring Rate
  
  1. Think about what you want most: comfort or performance.
  2. Research your car's weight. In general, heavier cars require stiffer springs to counteract the car's mass for the same effect that a lighter car with softer springs so base it in respect to chassis not spring rates alone.
  3. Research your car's suspension layout and factory rating. This is very important as different layouts will require different approaches to suspension selection and tuning.
  4. Research what is available in the market for your car.
  5. Compare the spring rate of the coilover you're considering to your factory spring rate, this way you can infer how much stiffer it's going to be.
  6. Check the coilover's damper valving/quality if possible. The stiffer the spring rate is, the better the damper's valving should be to compensate for the stronger springs.
  7. Choose the right one for you; refer back to the first point - softer for comfort, stiffer for performance. Additionally if the roads you drive on most are **** then it's not smart to run super stiff springs; instead go softer than normal. If the roads you run on are smoother, you can afford to run stiffer springs if you want more performance, otherwise stick with the norm and you'll be fine.
  
  
  
• Damper Adjustment - It may seem difficult to choose as the range of adjustments or steps for coilovers varies from 5 ---> 10 ---> 16 ---> 24 ---> 32.
  
  A larger number does not mean much, as a 32 step adjustment damper could actually feel like a 5 step adjustment damper depending on its quality. For example, a poor quality 32 step model could mean that several steps feel similar or no different like 1-6, 7-11, 12-18, 19-25 and 26-32.
  
  Therefore try not to focus on the how many step adjustments a damper has and hoping it can offset the harshness. Instead, focus on its quality, as this will determine how harsh the ride will be.
  
  
• Damper Quality - This is very hard to assess when you can't necessarily try and by. Fortunately there are a few key features, which can help differentiate a superior coilover from an inferior one.
  
  
  • Gas/Oil Type -
  • Piston Size - Piston sizing, especially for monotube, is a good way of judging how good the dampening can be. Coilovers with smaller pistons tend to not have precise dampening. In general, <30mm is considered small, 31mm - 45mm is considered medium and anything >46mm would be considered large.

Work in Progress

Coilovers: Initial Setup


After purchasing your shiny new coilovers, the next step is to install and adjust.


Height Adjustment




Damper Adjustment - Street

There are many ways of setting up dampers but here is a general, easy way of doing it. The assumption is that you haven't done this before, but once you have a few times, you will roughly know how to offset the front and rear damper settings.

N.B. The lower your car is, generally the stiffer you need to run the dampers to ensure the coilovers can sufficiently keep the car sprung, otherwise the car will bottom out.

• General Idea - For a street car, the safest way to increase handling performance is to ensure the tires are always kept in contact with the road under all circumstances. This is achieved by not running the stiffest setting (although this depends on the coilovers).
  
  
• Before Starting - After installation is complete, go get the wheel aligned.
  
  
• Starting - Start off by having the dampers set halfway for both front and back. Go for a drive on a route you know well, ideally with a mixture of smooth and rough surfaces to feel how the car reacts and also the damper's behaviour at different speeds.
  
  
• Tuning Procedure - Go for a test run each time you adjust a few clicks left or right then adjust accordingly. A 'few' means proportionate to the maximum amount of clicks. For example, let's say 10 clicks is the maximum. You initially set [F] 5 | [R] 5 and drive on your test route. You find it was too soft at the front and just a fraction too stiff at the rear, so you'd then try [F] 7 | [R] 4 and repeat the same route while noting the differences on different surfaces and at different speeds.
  
  
  • Tuning #1A - Front - Ideally the front dampers should be stiff enough to allow you to feel the road better but not so stiff that the nose bobs up and down, which causes the tyres to lose contact with the road and loss of steering feel.
    
    
    • Too Soft - A damper setting can be too soft when either the steering feel is too 'loose/gentle', lost altogether/when the car floats around like a boat.
      
    • Too Stiff - You will know it's too stiff when the nose of the car is too sensitive to changes in road condition, i.e. over bumps or reacting too harshly and exerts excessive force on the driver. It is also too stiff if it feels like riding a horse in general.
    
    
  • Tuning #1B - Rear - Ideally the rear dampers should be stiff enough to allow you to feel the rear following the front, but not so stiff that it feels nervous; especially during hard braking.
    
    
    • Too Soft - A damper setting can be too soft when either the rear of the car is not communicating to you as the driver or if it's not tracking the front correctly. Same as front dampers, it will also float around like a boat when too soft.
      
    • Too Stiff - A rear that is too stiff can usually be felt during hard braking, especially over bad road surfaces. If the rear tires don't feel like they're in contact with the road (a sensation like the rear is skipping or bouncing), you know you have to soften the rear dampers. As with the front, the rear will feel like riding a horse and obviously this is bad for your rear passengers.
    
    
    
  • Re-tune - You keep repeating this process until you attain or have nearly attained a desirable result. It is almost impossible to get the perfect setup unless both your car and coilovers are that good. In most cases you'll need to compromise.

Damper Adjustment - Track

• General Idea - For a track car, it's all about getting the sharpest feel to allow the driver to hit those apexes. Although there is little compromise taken, there are still some key points that need to be addressed.
  
  
• Car Spec - This may seem awfully strange, but the spec of your car will determine a lot of your setup. Differences in tires (Street ---> Semi-Slicks), chassis rigidity, driver preference, etc. all result in different setups.
  
  N.B. While going from street tires to semi-slicks provides a lot more grip, it also can introduce understeer. To counteract this, dampers, swaybar and suspension geometry should be altered to take full advantage of the semi-slicks' potential.
  
  
• Research the Track - Contrary to general opinion, not all circuits are smooth, especially older circuits. Some have not been resurfaced and along with undulated/off camber surfaces, this can have an impact on the setup so be sure to know what you're running on.

Work in Progress

Coilovers: List of Brands


JDM

In general, the average JDM coilovers tend to be stiffly sprung and under-valved. This is due to the excellent roads that Japan has, which allows manufacturers to run a firmer/stiffer setup than someone outside of JP would use. Some local distributors/dealers, such as Fulcrum [Tein] in Australia, offer models re-tuned for local conditions.

• Amuse [S2000]
• APEX'i
• Bilstein Japan
• Blitz
• Buddy Club
• Cusco
• CRUX
• Ennepetal
• GAB
• HKS
• Honda Twincam/FEEL'S
• J's Racing
• JIC
• KYB
• M and M Honda
• Mugen
• Ohlins Japan
• Quantum
• Revolution
• RS*R
• Seeker
• Spoon
• Tanabe
• Tein
• Techno Pro Spirit
• TODA
• Trust/Greddy
• Zeal/Endless

USDM/CDM

• AMR Engineering
• Function & Form
• Fortune Auto
• Penske Racing
• Skunk2

EDM

• APEX
• Bilstein
• Eibach
• Koni
• Nitron
• Ohlins
• Quantum
• SPAX

TDM - Taiwanese

• D2 Racing
• G4 Racing

Work in Progress

Vote for thread to be stickied

^ Yup would rep +100 points if possible.

Thanks so much guys =D

If you have suggestions or anything please post up and I'll try to add it if I've got enough of a grasp on it.

The other thing that should be added to this would be peoples personal experience (non of this my mate had blah blah)

Could be something along the lines of:

Model &amp; year
Set up (street, weekend warrior or track)
Brand &amp; level (eg: Tien flex or monoflex)
Spring rates
Ground clearance
Score out of 10
Comments

That sounds like an idea, might be better for another thread though perhaps?

Cause I wanted to keep this purely informative and a guide.

So perhaps start another thread similar to the Recommend a Tyre Thread?

Monotube is a better shock rather than the twintube.

Quote:

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Originally Posted by neut

Monotube is a better shock rather than the twintube.

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Please elaborate as both have their pro's and con's