Montreal Subaru Club

J'ai trouvé cela sur un lien d'un lien d'un quote sur un forum englo...
et je me disais que c'est une bonne base pour le noob:

This FAQ :

This FAQ constitutes the second part of the Spring/Strut/Coilover FAQ. It is very important to mention that the general suspension theories have been addressed in the prior FAQ and form the basis for this one. Even if you are an advanced user, you will benefit from reading the other FAQ, especially the links contained within.

Another thing to consider with this FAQ is that while this covers 100% of the different types of suspension upgrades, this does not mean that the novice to advanced user needs all or any of these upgrades. This post is solely designed to avail people to all the different upgrade types and allow you to find an upgrade that fills a suspension deficiency in your vehicle.

Topics that apply to all suspension and driveline upgrades:

Many suspension upgrades incorporate the replacement of the OEM component’s use of rubber bushings with those of polyurethane bushings. Sometimes this bushing type is referred to as “poly” or “urethane” for short.

Rubber is a natural material that can compress and change its volume with load. Polyurethane on the other hand is a synthetic compound that acts like a liquid; that is, its volume stays constant so it cannot be compressed. As an example, a squeezed rubber ball will shrink in size relative to how hard you squeeze it and a polyurethane ball will simply try to squeeze out between your fingers.

Rubber works very well as a noise and vibration dampener as it can actually seem to absorb energy although ultimately it does convert kinetic energy to heat. Polyurethane, on the other hand, needs to move in another direction to accept the load. It too will heat up, but it will work much more effectively as a bearing surface than rubber. Rubber perishes over time and will break down if contaminated with chemicals like grease and oil. Polyurethane on the other hand is relatively impervious to chemicals.

Rubber bushings are often made with the inner and outer shells bonded together using the rubber compound. The rubber is allowed to flex and distort by twisting, while acting as a damper for NVH. Most polyurethane bushings that replace rubber bushings are simply pressed in between the inner and outer shells, without an actual bond. Even if bonded, it will only ever be to one surface, as the material will try to tear itself apart if bonded to two surfaces. Unlike rubber, polyurethane operates with a bearing surface allowing one side to turn on the bushing relative to the other. Stated another way, polyurethane bushings have a free pivoting point and not a torsion pivot, as is the case with rubber bushings. This is why the use of white lithium grease is so important with polyurethane bushings.



A common term associated with polyurethane bushings is durometer, sometimes referred to as duro. Durometer is the relative hardness of a plastic material. This allows for comparison of aftermarket bushings to OEM units or aftermarket vs. aftermarket for determining what level of firmness the end user desires. Durometer is both a very scientific and ambiguous measurement as it can be measured via different scales; of which, there is no correlation. It is also not possible to say that Component A with a durometer of 55 is XX% firmer than Component B with a durometer of 45. One can merely state that higher numbers on the same scale are “firmer” than lower numbers on the same scale.

Durometer is also closely tied to the suspension acronym of NVH. Noise, Vibration, and Harshness is the term applied to the amount of noise, vibration, and harshness seen by the driver after upgrading their suspension. NVH is a very subjective term though. Realize that most suspension upgrades come with varying increases in NVH and are worthy of research. While you may love the feeling of swapping out 20 OEM rubber bushings, your wife and her scrapbook club members may have another opinion!

As to bushing types in suspension components, there are two choices: spherical and polyurethane. Spherical bearings are also known as pillow ball mounts. Spherical bearings are usually all metal with some of the more costly ones having a phenolic or Teflon liner to keep them running smooth. They will transfer almost 100% of the load and as well, they will usually transfer a lot more NVH. They have a bit more articulation than polyurethane bushings. When used on an endlink application, stop collars will be needed to keep the bar from walking side to side. When using a polyurethane bushing, the sway bar will self align and will keep balance from side to side. In addition, they will normally run with a lot less NVH since most of the vibrations will be absorbed in the polyurethane bushings instead of being transferred to the chassis. Aerospace grade polyurethane should outlive the life of the car with little to no service needed on the parts. A spherical bearing should have the same lifespan if keep lubed and clean of road salt and debris. If they do get debris in the bearing surfaces they tend to deteriorate rapidly.

Whiteline article on bushing composition:
http://www.whiteline.com.au/faqelse01.htm

Suspension Upgrades

Sway bars

Sometimes referred to as anti-roll bars or stabilizer bars. This is a very popular suspension modification.

Larger sway bars have two main effects. They change the vehicle balance in terms of understeer or oversteer, and increase roll resistance. Both of these attributes can provide increased overall grip.

Most factory vehicles are biased towards understeer, so the fitting of a larger rear sway bar will help in providing a more neutral characteristic in the handling. This is due to the increase in roll stiffness at the rear, which loads the rear wheels more unevenly and provides slightly less grip at the rear than previous. The reason for this is the rear end is resisting more of the roll, the front end resists less in proportion, leaving the front wheels more evenly loaded, therefore more available front end grip, which reduce understeer.

A sway bar (either front or rear) is designed to increase wheel rate and thus decrease body roll in the process. In Subarus specifically, this leads to a drastically better change in suspension geometry for lateral grip. Off-roading is not recommended with much of a sway bar; thus rally drivers often use very light bars or none at all to gain maximum wheel travel.

Cons of a bigger front sway bar: Very slight decrease in the affected wheels' range of motion. If not paired with a larger rear bar, an increase in understeer at the limit. Some report a very mild NVH increase; most don't. Biggest complaint is typically squeaking from improperly greased bushings.

Pros of a bigger front sway bar: Faster turn-in response. Camber curve improvement thus resulting in higher levels of grip, despite the car understeering a bit more at the limit. The limit was pushed higher by the addition of the bar, hence folks saying "It understeers less." Better overall transition ability.

Cons of a bigger rear sway bar: The rear of the car is looser and thus more prone to snap oversteer. The car also doesn't recover as well in rapid maneuvers. Some report a very mild NVH increase; most don't. Biggest complaint is typically squeaking from improperly greased bushings.

Pros of a bigger rear sway bar: The rear of the car is looser. Gain in camber curve is the same as with a front bar. The loading of the rear tires with extra weight transfer is what causes the traction loss in the rear. Most report "being able to get the tail out on command" but this is not necessarily safe in emergency maneuvers; only in horseplay.

As mentioned above, the larger front bar keeps control of the camber curve. The camber curve on a WRX is as such: As the body rolls, camber is lost and thus the tire rolls under and becomes entirely dependant upon the tiniest edge of the outer tread on the front tire under load. Any change that can improve this camber curve is typically good, but as with all things suspension is a compromise.

Sway bars are seen as a good method as they typically do not affect ride quality on roads; essentially body roll is the single largest change one can do to help improve the camber curve and increasing the effective spring rate at the wheel (AKA wheel rate) can be done with sway bars.

Springs can accomplish a lot of the same things, but with adverse affects on ride quality and in more extreme cases can heat up a tire unnecessarily on seemingly smooth road. Higher wheel rates also slide more easily; hence why drift cars typically have extremely high spring and bar rates.

The two major styles of sway bars are solid and hollow. The major differences between the two are weight and strength. Hollow sways bars weigh less than solid and solid sway bars are stronger. Both of these points can be argued though, depending on the manufacturer and end users’ experiences. In general though, either would be a fine choice with no real clear cut favorite.

Wagon owners: The 2002 and some 2003 WRX sedans came equipped with a 20mm rear sway bar. The owners of these models years who have upgraded to bigger bars are a wonderful source for a cheap upgraded sway bar over your OEM 17mm sway bar. Remember to purchase OEM or aftermarket 20mm sway bar bushings for best fit when using a 20mm OEM sway bar though.

ButtDyno's Swaybar FAQ
Discussion on larger sway bars
Whiteline sway bar paper
Whiteline hollow vs. solid sway bar paper
Hotchkis hollow vs. solid sway bar paper
This article describes the % of rigidity change from one size sway bar size to another.
This article shows a cheap sway bar bushing mount upgrade for 02/03 WRX owners.

Sway bar manufacturers:

Though too numerous to fully list, here are the major manufacturers:
Whiteline
Poltec
Cobb Tuning
OEM Subaru
Hotchkis
Perrin

End Links

Sometimes referred to as drop links. This is a very popular suspension modification.

In order to discuss the function of end links, one has to consider how they work in conjunction with a sway bar. The entire purpose of a sway bar is to act as a torsion spring. In order to do this you need some way to twist it. That twisting ability is provided by a bent "lever" at each end of the bar and allowing that lever to be pushed and pulled by attaching it to a suspension component that moves up and down. Since we're talking about the rear we'll look there. In our case, the attachment points that Subaru uses is on the rear lateral link. Basically, the end links connect the lateral link to the sway bar. When the lateral link moves up and down, it provides force on the drop link, which provides force on the sway bar. This twists the bar, and allows it to do its job. All of this is fine except for two problems. First, the length of the stock links may cause some problems with the fuel filler tube, and second they are way too soft. With full suspension travel, you run the risk of the end of the sway bar hitting the fuel fill neck. This is especially true if your car is lowered. Also, the stock rear links are made from plastic. The OEM unit flexes quite easily, even under minor loads.

Aftermarket rear end links help solve these two problems: some feature a length that is shorter than the stock links to solve the fuel filler neck problem, and they are considerably stiffer than the stock links. Made with bodies that are water jet cut from aluminum, extruded aluminum, or CNC manufactured, they are incredibly stiff when compared to the stock pieces. This stiffness in turn allows the motion from the rear suspension to be applied to the rear bar. This allows the sway bar to operate to its full potential, and apply forces where necessary.

Wagon owners: Get a great, cheap upgrade by switching to the sedan metal front end links over your stock plastic front end links. While there are few aftermarket front end link solutions, those are best left to the more advanced suspension people.

End links manufacturers:

Though too numerous to fully list, here are the major manufacturers:
Kartboy
Whiteline
Perrin
Poltec

Strut Bars

Sometimes referred to as strut tower bars.

The technical reason strut bars are desired is that vertical loads from the wheel pass through the strut and spring up to the strut top and towers, which leads to flex in the sheet metal around the strut tower and inner guard. Chassis flex is not conducive to firm response in a vehicle. Installation of a strut bar between the front and/or rear strut towers eliminates this flex. The result is faster and firmer response to steering inputs. Most users report this to be a very minor suspension modification ranked further down on the suspension modification path. On the other hand, the proliferation of inexpensive replica/eBay bars and aesthetically pleasing strut bars make this a common modification.

Wagon owners: Whiteline makes a specific rear strut bar with a quick release coupling that allows easy removal for times when you want to utilize the extra space that folding down the rear seats provides.

Whiteline article on strut bars

Strut bar manufacturers:

Though too numerous to fully list, here are the major manufacturers:
eBay
STi
Cusco
Whiteline

Underbody Braces

The primary purpose of aftermarket underbody bracing is to increase structural rigidity. In some cases these may add to the vehicle weight, so one must balance this against the increased suspension responsiveness that bracing imparts. Below are the major underbody braces.

Lower arm brace also known as a ladder brace or an H brace. This brace ties in the left and right half of your vehicle’s front subframe. Depending on the design, it may also connect the front subframe with the center of the cross member. These are all designed to stiffen up the front end. The only downsides to this mod are increased weight, and depending on the manufacturer’s design, decreased access to the transmission drain plug and/or inability to fit a vehicle equipped with an ALK.

Sub Frame Replacements are designed to reduce vehicle weight and through brace design, increase rigidity. Considering the front subframe weighs in at 50 lbs., this type of brace can save a considerable amount of weight on the front end of the vehicle.

Lower arm brace manufacturers:

eBay
STi
Cusco
Laile/Beatrush
Tanabe

Sub frame replacement manufacturers:

Do-Luck
GT Spec
Perrin
Laile/Beatrush
Carbing
M1
RPM

B pillar brace

Though designed originally as a harness bar for the use of racing harnesses, it also serves as an interior brace. Their mounting surfaces on the inside of the vehicle serve to stiffen the interior chassis longitudinally through the B pillars, just behind the front seats.

B pillar brace manufacturers:

GT Spec

Fender Braces

Sometimes referred to as side cowling stays.

These braces tie the lower A-pillar to the upper front frame member to triangulate the junction between the two. They replace the flimsy, stamped steel pieces that comes stock on the car. The genesis behind this product is to stiffen the upper front end of the vehicle. While the stock pieces do their job for most users, their weakness becomes apparent to many drivers. This is due by comparing the structural strength of the large, metal subframe supporting the bottom front of your vehicle vs. the smaller, weaker OEM fender braces that support the top front of your vehicle. The weak link was soon discovered to be the fender braces.

According to product descriptions, the brace will aid in initial turn in, responsiveness to sudden direction changes, a truer line through corners, and more confidence inspiring handling since the top chassis rail does not undulate as much or at all. Though a relatively new suspension mod, users are very, very enthusiastic about such a simple modification.

Fender brace manufacturers:

Turn in Concepts
STi
GT Spec
JDM Importers
Happi Motoring (link goes to retailer)
Jspeed (link goes to retailer)
Nagisa Auto
Creative Werks Inc.

Bushing Swaps

There are numerous bushing throughout the OEM suspension that may be swapped out. The purpose of this is to replace the softer OEM rubber bushings with firmer polyurethane bushings. This swap, for some people, constitutes enough of a change over the OEM characteristics to suit their needs. In some cases, a bushing swap represents the only upgrade available as there is no complete aftermarket replacement part. Some bushings are easily replaced, while others require either a vise or a hydraulic press to remove and press fit in new bearings. This requires research by the end user as sourcing a shop with the capability to press fit bushings can be challenging.

Bushing manufacturers:

Whiteline
Noltec
SuperPro
STi
Energy Suspensions
Prothane

Trailing Arms

Generally made of machined, lightweight aluminum, these replace the heavier OEM units, though the upgraded STi units are steel. Pillow ball (spherical) joints provide for significant improvement in handling response, and driving feel. The main reasons for this upgrade are the decrease in unsprung weight and tightened feeling of the improved joints. Mainly seen to increase feeling when going over bumps or elevation changes. While worthy of consideration, this modification is generally catered towards the more advanced suspension people.

Trailing arms manufacturers:

JIC
Cusco
STi
Poltec
OBX Racing Sports
Nagisa Auto

Lateral Links

Generally made of machined, lightweight aluminum, these replace the heavier OEM units, though the upgraded STi and Whiteline units are steel. Reinforced rear outer bushings, along with pillow ball (spherical) joints or full pillow ball construction provide for significant improvement in rear alignment control, handling response, and driving feel. The major differences in the different brands are the use of lighter weight and stronger materials such as carbon fiber and titanium, types of bushings, and adjustability, such as single or double adjustability. Aside from the benefits of reduced unsprung weight these components give, another main benefit is the increased adjustability for alignments with respect to camber and toe; also reduces changes in camber and caster when cornering. While worthy of consideration, this modification is generally catered towards the more advanced suspension people.

A cheaper alternative to those on a budget is to upgrade to 2005+ WRX or STi aluminum lateral links with or without a polyurethane bushing upgrade. This will decrease unsprung weight without the adjustability, provide a firmer suspension when used in conjunction with upgraded bushings, and be easy on the wallet. This is especially true for the front lateral links as there are no current aftermarket replacement units.

Wagon owners: take special note as wagon lateral links differ from sedan ones. Either the wagon specific or GC8 fitment works fine.

Lateral links manufacturers:

JIC
Cusco
STi
Poltec
Whiteline
OBX Racing Sports
Perrin
Nagisa Auto

Aluminum Control Arms

Source of unsprung weight reduction through the use of lightweight aluminum vs. the heavier steel stock units. Due to slight design changes, they are also stronger than the OEM components. There are differences in aluminum control arms though. The 2004 or older JDM control arms provide less caster than the 2005+ models due to suspension changes. While worthy of consideration, this modification is generally catered towards the more advanced suspension people.

Wagon owners: due to the sedan’s wider track, you should source the JDM GC8 aluminum control arms. Sadly, these are 2-3 times the cost of the sedan arms. As well, it may be worth your time to switch to a sedan sway bar due to this reason. If you do use sedan control arms, they will fit but will cause negative camber issues and possible issues with premature wear on front axle hubs. The only "correct fix" is to get the sedan front suspension to include the sway bar, end links, front axles, and spring/struts. As well, you should source 2004 and below arms as the 2005+ cause even more camber issues than their earlier cousins.

Aluminum control arms manufacturers:

STi
Nagisa Auto

Camber Plates

Camber plates replace the suspension top hats and allow for the adjustment of camber and/or caster. Typically, they feature a spherical bearing for the strut top to bolt through, and the hat portion bolts into the stock locations on the strut tower. Some feature an all metal "race only" design whereas others have some kind of damping built in to allow for some modicum of NVH absorption (lets be honest here, if you're running these then NVH probably isn't on your top list of concerns). The basic premise is the same for all of them; they allow for moving the top of the strut assembly to differ from the stock geometry. This changes the angles of the whole assembly to allow for the addition or subtraction of camber and/or caster.

Sounds simple right? Well, yes and no. While the theory is easy to understand there are some design factors that need to be considered when looking at these plates. There are two prevailing designs, one that allows for just camber adjustment and one that allows for both camber and caster adjustment. Here's how they work:

For just camber adjustment we have to look at the main parts. Aside from the various nuts and bolts there are two pieces that do the work. The first is the strut carrier. This is the part that actually bolts to the strut top. It will typically feature the spherical bearing that the top of the strut goes through and has a shape that makes it look like it has "wings." These wings are what bolt to the adjustment plate. The adjustment plate is typically triangular in shape and at each corner is a captured stud. These studs are what bolt it to the strut tower. In the face of the plate will be three rectangular slots. A large one in the middle, and parallel to this on each side is a narrower slot. The large middle slot accommodates the spherical bearing of the strut carrier, and allows it to stick through the plate. The more narrow slots line up with threaded holes on the wings of the strut carrier. When the assembly is bolted together, it bolts through these slots and into the wings that hold the strut carrier to the adjustment plate. When the entire assembly is bolted into the car, the rectangular slots run perpendicular to the centerline of the car. By sliding the strut carrier along the slots the assembly allows the top of the strut to move in toward or out away from the centerline of the car. This allows for the adjustment of camber by changing the angle of the strut assembly inward or outward relative to the centerline of the car.

It is important to note that while this design allows for just camber adjustment it is possible to install them to allow for camber and caster adjustment, but it will not allow for independent adjustment of each. When installing the adjustment plate, it is possible to turn the plates 120 degrees so that the slots are no longer perpendicular to the car's centerline. Instead by orienting the slots so that they run at an angle to the car's centerline it is possible to adjust the strut top at an angle. This has the effect of moving the top of the strut in/out and back/forward to increase or decrease camber and caster at the same time. Because of the nature of the design when you install it in this manner you cannot adjust camber without affecting caster. While it seems that this configuration may at first glance be the holy grail of caster/camber plates there are some things to consider. First, you cannot adjust one setting without affecting the other (for truly hardcore suspension geeks this is a bad thing). Second, in this configuration you will not be able to set as much camber or caster as you would by going with the second type of plate explained in this document. Racecomp Engineering, Hotchkis, and Cusco make plates that follow this camber only design.

The second type of plate is one that allows for independent adjustment of both camber and caster. The key word here is independent. It's possible to adjust either camber or caster without each affecting the other. There are many different designs when it comes to this type of setup. Some use a "floating plate" design. Some use an elliptical locating plate design. Some use a compound philosophy of the camber only plates. These are the
most common ones, and we'll look at each by specific manufacturer.

The Noltec (MRT units are rebranded Noltec) units use a floating plate design. In this case the strut carrier is a large plate with a spherical bearing in the middle. This plate is sandwiched between two rings. The rings have bolts through them that attach to the stock mounting points on the strut tower. This plate "floats" between the rings until the desired adjustment setting is reached. When the strut tower bolts are tightened the rings clamp on the strut carrier, and hold it in place, thus keeping the floating plate from moving.

The PDE and DMS units use a rather unique elliptical plate with a locator pin to hold the settings. On the strut carrier is a plate with holes bored into it according to an elliptical curve pattern. The strut carrier sits on a strut tower plate, and allows the strut carrier to float in place. By choosing a hole on the elliptical plate it is possible to choose a variety of settings that allow you to set camber and caster independently by predetermined amounts.

The Ground Control plates are very similar to the camber only plates listed above. Just like the camber plates they have a strut carrier that slides in the adjustment plate. The difference is the adjustment plate does not have captured studs. Instead a ring that mounts to the bottom of the strut tower holds the captured studs. The adjustment plate sits on top of the strut tower, and has slots parallel to the car centerline. So essentially, the strut carrier slides in and out on the adjustment plate, and the adjustment plate slides forward and back on the mounting studs.

When considering camber/caster plates there are a couple of other things to think about. Almost all the designs will add ride height to the vehicle due to the thicker than stock design. The two exceptions to this are the units made by Racecomp Engineering and Hotchkis, which are designed with this in mind, and will not raise the overall height on the vehicle. The other thing to consider is alignment settings. You can't just go shoving the top of the strut all over the place without affecting toe, which up until this point we have not mentioned. Before you jump into getting camber/caster plates please understand their full effects, and the principles of alignment adjustment.

Camber plate manufacturers:

Racecomp Engineering
Cusco
Hotchkis
MRT
PDE
DMS
Ground Control

Camber Bolts

This is a very popular suspension modification.

Camber bolts are suspension bolts that not only hold your struts to the vehicle, but also allow varying degrees of camber adjustment during alignment procedures. Most Subarus come with camber bolts in the front. Many users install rear camber bolts and/or replace the front ones with aftermarket units that allow a wider range of adjustment. There are quite a few manufacturers of camber bolts that offer a variety of adjustment ranges outside the 2 degree “standard” of adjustability. The “standard” rear size is to get a 12mm camber bolt (with an eccentric lobe) to fit the 14mm hole.

Camber bolt manufacturers:

Though too numerous to list, here are the major manufacturers:
Whiteline
Noltec

ALK

This is a very popular suspension modification.

The function and use of an ALK can be best explained by referring to the ALK FAQ.

ALK manufacturers:

Perrin Positive Steering Response System (P.S.R.S.)
Whiteline Anti-Lift Kit (ALK)
GT Spec Antilift Kit
STi Transverse Link Bushings*
STi Group N Transverse Link Bushings*
Whiteline KCA375 offset Transverse Link bushings

*Though listed separately, both "versions" of the STi transverse link bushings are identical as they share the same part number.

Subframe Lock Out Bolts

Rear differential/chassis cross member bolt up kit. Removes compliance with rubber mounted rear diff carrier.

Subframe lock out bolt manufacturers:

Whiteline
Perrin

Top Hats

These are a very popular suspension modification.

Top hats are the connection between the top of the struts and the vehicle chassis. Due to the OEM unit’s soft rubber compound, there is a lot of compliance. This compliance contributes towards a softer and less responsive feeling in the suspension for many owners. The only two choices for upgraded top hats are the STi and the STi Group N top hats. The STi top hats are firmer than the OEM units and the STi Group N (JDM) top hats are the most firm. While one can get the STi top hats from any Subaru dealer, the Group N version can only be obtained through a vendor that has the ability to import JDM components. This can be a point of confusion with people shopping; as the important and frequently overlooked detail is the presence or absence of the words “Group N”.

Top hat manufacturers:

STi
STi Group N

Other braces and bushings

A few manufacturers make unique or hard to name braces or bushings that really need to be seen and may be worthy of researching that haven't been included as major things to consider. View the below manufacturers to see their content.

Laile/Beatrush
Cusco
GT Spec
Do-Luck
Nagisa Auto

Driveline Upgrades

Short Throw Shifter

This is a very popular driveline modification.

The Subaru shifter assembly serves the same purpose of every other shifter assembly for every other car in the world. It allows a control mechanism for the driver to select what gear the transmission is in. The two most popular mechanisms out there are a rod controlled selector, and a cable control selection. Starting in 1997 all the Subaru manual transmissions use a rod-controlled selector.

Starting from the top and working down: At the very top of the shifter assembly you have the shift knob. It's that thing you put your hand on. Below that is the shift lever. About half way down on the shift lever is the connection for the control rod. This is commonly called the control rod fulcrum. The control rod is what goes to the shift linkage, which allows for smooth pivoting, and connects the lever side control rod to the transmission side control rod. The linkage serves to allow for the lever side control rod to work at various angles, but transforms the motion into straight forward/back motion while still allowing for twisting. This forward/backward motion, along with the twisting is what moves the transmission side control rod. This motion of the transmission side control rod is what allows the shifter fork inside the transmission to move, and thus allows you to select gears.

Now, moving back to the shift lever look at the control rod fulcrum, and follow the path down the lever to the bottom of the shift lever. There you will see that the lever ends in a ball shape. This ball shape rests in a plastic cage, and provides the fulcrum for the lever to move. After all, you can't have a lever without a fulcrum. Now, here's the thing. That cage isn't just hanging out there in space. It has to be attached to something. Ideally you want that something to be as stable as possible. That's where the shifter stay comes into place. If you look at that plastic cage you will see that it's contained in a metal cup. Attached to the metal cup is a metal rod. This metal cup and rod is known as the shifter stay assembly. Now, to make that assembly as stable as possible Subaru achieves this by attaching each end of the stay rod to something on the car to try and keep it from moving. At the front of this rod is called the front stay, and the rear of this rod is known as the rear stay. The front stay is mounted to the transmission bell housing through the use of a bracket, and the rear stay is mounted to the body of the car up in the transmission tunnel. Each mount, both front and rear, has a bushing that is used to add comfort and cut down on NVH.

Short throw levers are available in a number of versions depending upon your model car, and transmission installed. While there is only one version for the STi 6mt, there are a number of levers to address the setup of the various Subaru models. All the lever components are CNC turned from Chromoly and the final assembly is tig welded for the best in strength and durability. Please note that these are not just stock levers that have been cut down. Instead the location and position of the control arm fulcrum has been evaluated to provide for the best possible mechanical advantage, while still offering a shortened upper portion. This provides for a great balance between the length of the throw, and ability to shift the lever with minimal effort. Overall all the levers are shorter by 1" or more and produce a 10-40% reduction in throw when compared to the stock lever.

The aftermarket STi short throw shifter is worthy of mention as this is sometimes a factory option. It is the only short throw shifter that also replaces the stock linkage with strengthened components. This can be a selling point for some, but seeing as there has never been a documented case of the linkage being broken, it’s “better linkage”, minimal throw reduction of 10%, and extremely high cost just don’t pass the “buy test” in most Subaru owners’ eyes. Even owners of this shifter can purchase an aftermarket short throw shifter and feel the benefits of an additional 30% reduction in throw length. In this case, WRX owners should buy the GC8 (RS) version as the improved linkage changes the shifter linkage from WRX width to RS width. For STi owners with the STi short throw shifter, you just purchase any aftermarket STi 6MT short throw shifter and it will bolt right up. If you are unsure if you have this option on your car or not, remove your shift knob, slide down the leather shift boot, and look at the metal shaft. Gold in color on the 5MT or olive drab green on the 6MT indicates the presence of a STi/SPT short throw shifter.

Short throw shifter manufacturers:

Kartboy
TWM
B&M
Perrin
DC Sports
GFB
STi
Cobb Tuning
Subydude
AVO

Steering Rack Bushings

This is a very popular suspension modification.

The reason for this upgrade’s popularity stems from the inexpensive cost and overall appeal of this modification. It replaces two very soft rubber bushings that hold the steering rack to the vehicle chassis. These are replaced by much firmer polyurethane bushings. The result is a firmer feel in the steering wheel and a decrease in the amount of slop in the steering wheel to inputs.

Steering rack bushing manufacturers:

Whiteline
Noltec
SuperPro

Outrigger Bushings

Like a lot of the bushings on our cars, the ones in the rear subframe outriggers are way too soft for a performance-oriented driver. In this case, the softness is demonstrated in a loud clunk from the rear of the car during launches or high RPM or fast shifts. What happens is this: the rear diff torques, slamming it around in the mount. This in turn, slams into the subframe. Instead of the energy going to the wheels, it travels through the subframe looking for the path of least resistance. In this case, that path of least resistance is to the outriggers of the subframe. The softer the bushings, the easier it is for that energy to flex things, and in this case flex so much that the outrigger slams into the bottom of the car causing the “clunk from the trunk”.

Rear subframe outrigger bushings are designed to help resist that energy, and keep the outrigger from slamming about. The aftermarket units are made from aerospace grade urethane. How much stiffer they are than stock is infinite because they go into a spot where there is a void on the stock car. See, what Subaru did was put the bushing in the ends of the outrigger leaving some big voids at the top and the bottom. The OEM bushing is so soft that the outrigger slams about into those voids. Aftermarket bushings fill that void by sandwiching the end of the outrigger, allowing for the cushioning of the blow, and solving the noise. A nice side benefit of these is they further tighten the driveline allowing for better feedback to the driver. Additionally, if you have a trunk monkey he will be much happier once you install these since he won't get headaches from the outrigger constantly slamming into the body of the car.

Outrigger bushing manufacturers:

Kartboy
Whiteline
Noltec
Perrin

Shifter Bushings (front & rear)

These are very popular driveline modifications.

The front and rear shifter stay bushings address a shortcoming of the stock setup at each end of the shifter stay. At the front is a loop through which a bushing is pressed. This bushing is then bolted into the bracket that is attached to the transmission. At the other end, the rear of the shifter stay is yet another bushing. This one connects the shifter stay rod to the body of the car, thus stabilizing the rear portion of the stay. Both the front and rear stays suffer from the same problem, they are too soft.

Ideally, you want the shifter stay to be as stable as possible. The problem is that the stock bushings deflect too much. This shifts the fulcrum point upward on the lever from that ball and socket connection. This change in the lever moment causes vagueness in the feeling, and makes for a more difficult shift. While it would be possible to rigidly mount the front and rear of the stay this would introduce so much NVH into the assembly that it would be intolerable to even the most enthusiastic of drivers. Additionally, by hard mounting the front and rear you would introduce too much stress upon the shifter stay rod. Remember the stay is attached to the transmission at one end, and the body at the other, and the transmission moves. Hard mounting would solve the deflection problem, but would lead to the eventual failure of the shifter stay assembly. This is where the front and rear shifter stay bushings come in to play. Made from aerospace grade urethane they are considerably stiffer than the stock bushings. This vastly improves the feel and function of the shifter by reducing the compliance of the bushings, but at the same time allows for enough motion for things to move as they need to.

Front shifter bushing manufacturers:

Kartboy
Noltec
Energy Suspensions
Cusco
Laile/Beatrush

Rear shifter bushing manufacturers:

Kartboy

Shifter Linkage Bushings

These bushing are pressed into the shifter linkage, and are designed to eliminate the side-to-side slop in the shifter. Please take note; these are not for the shifter stay assembly, but for the actual articulated joint in the gear selector assembly.

The problem is the stock bushings are made of soft rubber that has a tendency to degrade in performance over time. This degradation leads to poor fit of the components, and less damping due to increased gaps. This in turn leads to a very sloppy action in the stick. This sloppy action leads to poorly defined gates, missed shifts, and a cheap feeling in the shifter.

The shift linkage bushings are designed a bit oversized to allow for interference fits, tighter tolerances, and more resistance to compression by the virtue of there just being more material pressed into the assembly. This design coupled with using very stiff polyurethane instead of rubber has led to a much better feeling in the side-to-side motion of the stick, a much sharper definition of the gates, and a positive click upon engagement of the shifter.

Shifter linkage manufacturers:

Turn in Concepts

Rear Differential Mount Bushings

These bushings fit into the rear diff hanger on the GD/GH chassis. It is important to note that these are not for the subframe outriggers, but for the actual mount for the rear diff.

The origin of this part was to eliminate the clunk from the rear of the car during hard launches, and high RPM/hard shifts. Research found that a large contributor to the clunk was the soft stock carrier bushings flexing too much and allowing the rear differential to move a drastic amount. A large contributor to this flex is not so much the material, despite being soft rubber, but the voids that exist in the upper and lower portion of the stock bushings.

Made from a very carefully selected stiffness of polyurethane for longevity, these pieces are unique to the market in two aspects. The first, and most important, is the split bushing design. By utilizing this split design this has eased the installation for the shade tree mechanic in that a press is not necessary to install into the hanger. Second is the bushing shape. Instead of following conventional wisdom and shaping the bushings exactly like the stock bushings, these bushings took a different route and used a fully flanged bushing with flat outer faces. This flanged design stabilizes the hanger from shifting or twisting by supporting the hanger mount edges. The flat outer faces allow for full surface contact with the rear subframe, further supporting the flanges, and creating a tighter fit of the entire assembly.

Overall, the bushings accomplish exactly what they are designed to do: eliminate the clunk from the rear of the car. They do this job very well with very little increase in NVH. Upon testing these it was also discovered they provide a very nice surprise benefit of a more connected feeling with the rear of the car. This allows for more control, and an elimination of some of the soft vagueness that seems to plague the rear end.

When coupled with rear subframe outrigger bushings, there is a mild increase in NVH, but the feedback and connected feeling is even further enhanced.

Rear differential mount bushing manufacturers:

Turn in Concepts
Perrin

Engine Mounts

Anyone who has seen a Subaru motor run can tell you the majority of motion under the hood is of a side to side fashion. While this is indicative of a boxer motor, physics tells us that any disconnected motion from its intended source is an energy loss. This does not mean that the soft OEM rubber bushings are making you lose horsepower per se, but many drivers prefer the increased feedback provided by stiffer aftermarket polyurethane mounts or the near direct connection provided by solid metal mounts. Though many enjoy the feedback provide by metal mounts, for some their associated levels of NVH can be too much for some.

Engine mounts manufacturers:

STi
Noltec
Cusco

Driveshaft Mount Bushings

Replaces the OEM bushings with solid metal ones.

Driveshaft mount bushing manufacturers:

Laile/Beatrush

Transmission Mount

In the same light as the engine mounts, the transmission mount is another source of driveline movement that many feel would benefit from a stiffer aftermarket polyurethane mount or the near direct connection provided by a solid metal mount. Though many enjoy the feedback provide by metal mounts, for some their associated levels of NVH can be too much for some.

Transmission mount manufacturers:

STi
Noltec
Cusco

Transmission Crossmember Bushings

The problem is that the transmission moves too much due to torque flex. This flex uses up energy that could be better spent elsewhere, like to the wheels. On top of this, there is the overall feedback to the driver of what the driveline is doing. A more solid driveline provides for more energy to be sent to the wheels instead of flexing bushings, while at the same time lets the driver know exactly what is happening. A number of people realize this which is why people are replacing the stock engine and transmission mounts with ones that are considerably stiffer than stock.

The transmission mount rides on a subframe that is bolted to the chassis. That subframe contains bushings. What you have done is simply moved where some of that energy is displaced from the mounts to the bushings on that transmission subframe. Stiffened engine and transmission mounts do improve performance and feel, but why only go half way? By replacing the soft transmission subframe crossmember bushings with the much stiffer ones, which are made from aerospace quality urethane, you further reduce compliance of the entire system. This reduction in compliance helps to drive the wheels, and allows for a driver, who is highly attuned to the car, to perform better by knowing what the car is doing.

Transmission crossmember bushing manufacturers:

Kartboy
Noltec
Laile/Beatrush

Pitch stop

This is the dog bone shaped component that is located under the intercooler. It connects the top of the motor to the top, rear of the firewall. It is designed to limit the up and down movement of the motor. Considering the majority of the engine’s movement during idle and load situations causes horizontal thrust motions; this component, in most people’s opinion, really doesn’t serve much purpose. Aftermarket units consist of higher durometer plastic, solid metal, or small dampener. While an upgrade from the OEM unit, this is generally an upgrade that is far down on the list of important upgrades.

Pitch stop manufacturers:

STi
JLM Motorsports
NRG Innovations
Ingalls
Laile/Beatrush

How do I install suspension or driveline components?

One should always use the manufacturer’s installation instructions for best results. For suspension components without instruction, one may refer to one or more of the following for assistance:

Search www.scoobymods.com
SPT site with various installation instructions
46MB video featuring steering rack bushing install (thanks nhluhr)
PDE’s camber plate installation instructions
Cobb Tuning installation instructions
Hotchkis Tuning installation instructions
Whiteline installation instructions
Kartboy installation instructions
Turn in Concepts’ installation instructions
scoobymods.com’s Kartboy instructions
Suby Dude's shifter instructions
6MT shifter instructions
EDO Performance tranny mount install instructions
Perrin Performance instructions for read diff bushings and subframe bolts
Trailing link install
Rear trailing link bushing install
scoobymods motor mount install

Editors Note

This post was created because I wasn't able to find a good Suspension or Driveline FAQ. I came up with the text based on LOTS of searching here. It was also created to be intentionally brand neutral so that it serves as a stepping stone for further research. Upon reading this you should have an idea of what type of suspension and driveline upgrades best suit your needs. The manufacturer is up to you.

If you find an error in this FAQ, please PM me with factual details and I will update this post. Responses such as, "I have XXX's end links and they are great!" or "XXX's sway bar broke after 1 month" are not appreciated here, that is what the Car Parts Review Forum is for.

Merci pour le post. Je crois que je vais y retourner souvent.

that is an interesting post, lots of detailed information. How come MSI is not listed, I believe they are a manufacture local to the montreal community ?
I have CUSCO trailing arms with MSI lateral links. The MSI stuff was expensive, but holy smokes, almost 2 years later and the bearings still are not making any clunking or noises!

Pourrais-tu linker le lien original, comme ça on pourrait s'y référer pour updates/comments/etc...

Post it?

Je le trouve pas mal éducatif comme post. Merci.

LEKO a écrit :Pourrais-tu linker le lien original, comme ça on pourrait s'y référer pour updates/comments/etc...

+1 et surement plus facile à lire aussi....
On s'entend pour dire que notre forum est assez laid à lire
Mets au moins de la mise en page (gras, couleur, etc.)



Anyway, pourquoi vous copier-collez les post des autres forums/sites
(vous = ceux qui font ça dans d'autre posts aussi)

C'est tellement plus simple de mettre un lien et centraliser l'info là où elle était et voir les updates

Pykar a écrit : Anyway, pourquoi vous copier-collez les post des autres forums/sites
(vous = ceux qui font ça dans d'autre posts aussi)

C'est tellement plus simple de mettre un lien et centraliser l'info là où elle était et voir les updates

Si la source d'information est privée ou nécessite un usager/mot de passe, c'est pas tout le monde qui peut l'acceder.

silverf0x a écrit :Si la source d'information est privée ou nécessite un usager/mot de passe, c'est pas tout le monde qui peut l'acceder.

Au moins, on doit donner le crédit à la personne qui a fait le post original. Au pire, le link va mener à une page de "login", mais au moins si quelqu'un veut aller lire l'original et la discussion qui s'en est suivi, il le pourra. Aussi, si l'auteur modifie son post, on pourra lire la toute dernière version en tout temps.

J'ai paster cela le Aoû 18 et ce n'est plus dans mon historique, mais je crois que c'est sur scooby mods. dans la section suspension !

si vous avez des sugestions ou voulez que je clean le poste original (du texte en caracter gras ou ajouter les lien vers de site de compagnie local ex.) je vais etre la !

source #1
http://forums.nasioc.com/forums/showthread.php?t=920405
source #2
http://forums.nasioc.com/forums/showthread.php?t=911257

Spring/Strut/Coilover FAQ

What can I find some good background information about suspension components in general?

How Stuff Works on suspension
Suspension bible
McPherson struts
Suspension dictionary
Suspension background information
Basic suspension modes
Suspension Basics (though it deals with RC cars, the theory applies)
Whiteline's suspension articles
Whiteline's FAQs

What are some books I can read on the subject of suspension modification?

How to Make Your Car Handle by Fred Puhn
Race Car Vehicle Dynamics by William F. Milliken & Douglas L. Milliken
Tune to Win by Carroll Smith
Competition Car Suspension: Design, Construction, Tuning by Allan Staniforth
High-Performance Handling Handbook by Don Alexander

There are two types of people who want to make suspension changes:

a. People who want to improve their car’s appearance.
b. People who want to improve their car’s handling ability.

The first approach is to accurately and honestly categorize yourself. This is the hardest step of the process and both types will be discussed in detail.

Appearance People: Congratulations on your choice, as there is nothing wrong with your decision. In order to help you make intelligent decisions, here are some generalizations to keep in mind:

Appearance people may be further sub-categorized by:

a. People who want to lower their vehicle a little to improve the looks and even out the wheel gap.
b. People who want to lower their vehicle a lot to remove most of the wheel gap and to have a 100% even wheel gap front to back.

For people who want to lower their vehicle a little to improve the looks and even out the wheel gap, the most commonly used products are STi non-JDM pink springs, (for the WRX), the STi JDM pink springs (for the STi), Prodrive, Tein H-tech, and Eibach. While there are other springs that may fall into this category and are worthy of research, these seem to be the most popular and are all considered by most users to be appealing, inexpensive, and fairly strut friendly when used with the OEM struts.

For people who want to lower their vehicle to remove most of the wheel gap and to have a 100% even wheel gap front to back, the most commonly used product is the Tein S-tech springs. These springs will really lower a Subaru as well as remove most, if not all, of the F/R unevenness. The main drawbacks to their use include decrease in handling due to the enormous change in the suspension geometry and severe decrease in strut life when used with the OEM struts. While there are other springs that may fall into this category and are worthy of research, these seem to be the most popular and are all considered by most users to be appealing,

Coilovers are the “best” suspension mod in that the struts are designed to work with the springs. This can be a misnomer though, as many people will then adjust their coilovers for appearance’s sake. Using this logic, people tend to think coilovers are a better route to go. The flaw in this logic is that while they are matched components, they are only matched within specific design parameters. You may adjust them outside those parameters, compressing the spring to get the look you want, and at the same time overpower the strut’s design capabilities leading to a drastic decrease in strut life. While you can use coilovers as an appearance mod, springs are a more cost effective option.

Spring rates
RavensBlade spring rate chart
Spring rates (with drop info)
Shock dyno

Handling People: You have a tougher road ahead of you than the appearance people . In order to help you make intelligent decisions, here are some generalizations to keep in mind:

Handling people may be further sub-categorized by:

a. People who want to improve their vehicle a little to improve the handling for spirited driving, limited budget owners, or novice to advanced racers.
b. People who want to improve their vehicle a lot to improve their handling for advanced to expert racers.

For either type of handling people, you have steps you should take prior to suspension changes that will serve you well as the first steps in your suspension modification path.

Step a: Tighten the nut behind the wheel. This often used expression, while humorous is very appropriate. You should attend classes on how to drive in your particular type of racing. This can be either formal training or informal training with a more experienced person.

Informal training can be had at local racing events. While 80% of autocross racing is actual racing, the other 20% is socialization. Get to know people; learn who the good drivers are. The key word is drivers, as you will find people with “economy” cars that embarrass “sports” cars. Also do not discredit age, race, sex, or appearance as cues to whom to approach with questions. As an aside, in my autocross days in the mid 90s running in Columbus, IN, the best driver was a man well into his 80s. He couldn’t get around very well, so he never walked the course and was always seated as the starter for each event. Behind the wheel of his black MR2 though, he was always had the fastest time of the day even against the highly modded, multi-winged go karts.

Ask drivers you admire to walk the course with you, ask advice, and do a ride along or two. For the most part, excellent drivers will be glad to pass along what they know. Unless you are in their same class that is.

Formal training can take place in several venues. Local racing clubs such as the SCCA and NASA hold formal national training and formal local training sessions throughout the year. Google search terms like driving school, auto training, etc. along with your city or closest major city name. There are also many “SCCA like” organizations that can fly under the radar and can be hard to locate. Talk to local autocrossers or local speed shops and ask them as most of them usually know the local clubs. Sometimes these organizations can be general or “catered” towards a specific car like BMW, Corvette, Porsche, etc. that will allow “outsiders” to join and participate. On a broader scale, you can look into national training through Skip Barber, Bondurant School of Racing, etc.

Aside from formal and informal training, your best course of action is practice. Don’t practice against the field, practice against yourself. Take care note of any vehicle changes and note how those changes affect your driving characteristics and times. A vehicle log can be a key piece of your suspension and driving puzzle.

Step b: Get an alignment. Sounds insanely simple, but is probably the most overlooked suspension modification. The real tricky part to this is the methodology for obtaining a good alignment. While you can shop around for days to find out which shop has the newest, wiz-bang Hunter laser rack, that machine’s weakest point is the operator. For alignments, here are your two best options:

Least costly: Find a shop that offers “lifetime alignments”. The initial alignment is usually pricey, but if you go there 3-5 times a year and you have a technician who knows your desires, it’s a real bargain. Talk to the technician, NOT the sales guy at the front desk. Find out the technician’s name, call him that from then on, buy him lunch or a soda and get to be his very best friend. Explain why you are there, the specifications you desire, and request a before and after print out if their machine has that level of technology. Express to him every suspension modification you’ve done and avail him to any OEM or aftermarket adjustment points such as camber bolts, camber plates, etc. as well as their correct operation. From that first day forward, you never schedule “an alignment”, you schedule an alignment by Chris Jones (for example) and by Chris Jones only.

Also realize that some big name service stations that offer lifetime alignments may turn away vehicles with modified suspensions. And just because Firestone over on Elm Street says it’s against company policy, doesn’t mean that Firestone over on Charles Street will too.

Most costly: Find a shop that specializes in performance cars and pay for each alignment. This advice can usually be gotten from your local NASIOC forum, local people, or local speed shops. Once again, use the above least costly advice for the best results. Courtesy towards your technician goes a LONG way for them to decide whether it’s worth 10 minutes of their time fiddling with your camber bolts for a .5 on a sheet of paper or not.

Alignment info (including DIY alignments)
DIY alignment

Step b. extra credit: Get some camber bolts. Your car probably already has some OEM ones in the front, but a set for the rear is around $40, so why not?

Step c: Tires. Research carefully and use a brand/type of tire that suits your driving application. In a perfect world, you’d have set of everyday wheels/tires and a set of racing wheels/tires. If you can only afford one set, ensure your tires are the best performance tires that suit your local weather pattern, rather than what you see at the track in June. Summer only or R compound tires are great on the course, but deadly in the snow or rain when you are driving with the wife, kids, and a trunk full of groceries. And remember…cold weather can affect sticky or summer tires in dry conditions just as badly as if it was snowing. If you can’t afford two sets, err on the side of caution and learn to drive within the limits your tires impose on you, on and off the track.

For people who want to improve their vehicle a little to improve the handling, the most commonly used products are and USDM or JDM STi takeoffs, Koni inserts or KYB AGX struts with good springs like those mentioned above. While there are other strut/spring combos that may fall into this category and are worthy of research, these seem to be the most popular and are all considered by most users appealing, inexpensive, and decent upgrade of the OEM units.

For people who want to improve their vehicle a lot to improve their handling, it gets a little cloudier. Generally speaking, here should be your progression path: you know how to drive your car; you have good tires, an excellent alignment, have modified your suspension, and are hungry for more assistance to supplement your setup.

Now it’s time to start thinking about coilovers. Coilovers are a matched spring/strut combo that allows the end user degree of customization. Most hate generalizations, but for the beginner, you will be best served by this flow chart:

Less Money...................More Money
Less adjustability……..More adjustability
More wife friendly…..Less wife friendly
Easier to set-up……...Harder to set-up

There are some negative aspects of coilovers. Most have a wear cycle. Unlike traditional struts that will wear for 60k or more miles, most coilovers have a rebuild cycle where you send them in to your Vendor or Manufacturer for rebuilding. This may give some people pause if they think that coilovers are a “permanent” suspension solution. As well, depending on the manufacturer’s design, adjustments can be a real pain to perform. Consider that you might have to do the following:
a. Jack up car
b. Remove tire
c. Adjust coilover
d. Replace tire
e. Lower vehicle
This can be repeated numerous times for each wheel and for each corner which can be a great source of frustration. This isn’t to say that there aren’t people out there who live for this type of suspension interface, but it serves as a warning to people who think coilovers are 100% bolt on, plug and play parts. It should also be a warning to those who think that going from a slammed look to a normal look is a 10 minute job.

For initial setup of coilovers, they should not lower the car past the point where the A-arms are parallel to the ground in 99% of cases. This means a good starting point to work from is 13.5” measured from center of hub straight up to fender lip all around is the lowest you want to go. You can adjust higher from there as needed via personal experience or corner weighting.

Another feature that coilovers allow you to do is corner weighting, also known as corner balancing. In short, corner weighting evens out your car’s suspension during turns so that your vehicle reacts identically in both left and right turns. It’s not so much a suspension improvement per se, as it equalizes your car’s handling characteristics in both left and right hand turns. This is accomplished by equalizing the weight applied to your tires’ contact patch on opposing corners via adjustments on your coilovers. LF + RR = RF + LR is the goal of corner weighting. While in a perfect world, this can be accomplished, in the real world, the goal is to get your vehicle as close to this as humanly possible.

Finding a shop that can perform corner weighting is sometimes a difficult task. Consult your local NASIOC forum, speed shops, or racing bodies to find the location of a shop. Ensure your car arrives in the condition that you normally race in, (e.g. remove spare tire, subwoofer, low fuel level, helmet, etc.). And also realize that corner weighting is a participation event and not something that you can drop off as a key component of corner weighting is the weight of the driver!

The counter weighting process will also give you some hard figures to consider if you wish to change the static weight distribution. This is the distribution of the weight with respect to the front to rear of the vehicle. LF + RF = LR + RR is the goal of static weight distribution. While this is nearly impossible with our front bias weight distributed cars, you can certainly make improvements in this area by:

a. weight reduction
b. weight relocation
c. ballast

Obviously, ballast (adding weight) is not the most favored route, but reduction is a common tactic. As well, relocation can affect corner weighting as well. For example, one might relocate their battery in the passenger’s side rear of their trunk. This shifts weight to the rear and to the right. For example, this may counteract the front static weight bias caused by the front engine design as well as the left corner weight bias caused by the driver.

Corner Balance (though it deals with the NSX, the theory applies)
Corner Balancing (though it deals with Porsches, the theory applies)
Understanding Corner Weights
Excel spreadsheet for corner weighting
NASIOC weight loss thread
Oakos Automotive’s weight list

Spring/Strut/Coilover notes that apply towards all people:

Suspension components are all about compromise. Here are the main points of suspension modification:

-Good looks (even gap/low drop)
-Ride quality (not too stiff)
-Performance (maximizing handling)

Realize that you will probably only get two picks from this list and the third will suffer.

Many spring or strut companies will say that their product(s) will lower your vehicle X inches or XX millimeters; take that with a grain of salt. Each vehicle, though factory made, has its own unique configurations that will change the output of an aftermarket suspension.

Wheel and tire packages, depending on the owner, can be enough of a change or alter the stance of a “looks OK” vehicle to a “looks perfect” vehicle.

It’s your vehicle. If you do nothing more challenging than hauling peat moss from Home Depot and you feel you need Ohlins coilovers just like what’s on the WRC car to do so, that’s 100% fine. Just realize the pros and cons of suspension changes prior to purchasing, as nobody wants to hear you whining when you are clunking around corners on a blown out strut caused by your ultra low springs.

Lowering your vehicle does have repercussions though:

Noise, vibration, and harshness (NVH) will increase.

When using springs on struts not designed for the increased spring rate, your struts will degrade quicker. The higher the spring rate, the quicker the strut degradation and the rate is not necessarily linier as it tends to be logarithmic. In plainer terms, a 40% increase in spring rate may result in a 110% decrease in strut life. Figures used are fictional examples as exact figures are nearly impossible to compute.

Tire rubbing may become an issue. This is especially true with wagon owners as the non-flared fenders and improper utilization of sedan springs on a wagon will/can exacerbate the problem.

Some states and localities have specific laws catered towards suspension modifications. Many times these laws are very ambiguous and fall under the broad category of “modified suspension”. You are best served by talking with local people via your local NASIOC forum to find out the state/local codes as well as enforcement of applicable codes.

Suspension shortcuts should be left to the high school kids. Cutting springs, heating springs, or other “hillbilly mods” to reduce ride height should NEVER be taken. Yes, we know racing professionals sometimes use these techniques for suspension testing, but their engineering degrees, controlled methodology, and testing equipment ensure a high level of safety vs. your Cousin Jimmy and his propane torch.

Wagon owners: Yes, it’s true that in every aspect, wagons are superior to sedans. That being said, due to the slight weight increase in the rear end vs. the sedan, you should get wagon specific springs. While not 100% mandatory, realize that utilizing sedan springs on a wagon usually means a slightly greater rear drop that can negate some/all of the “leveling” ability of aftermarket springs.

What about OEM/JDM/new model year suspension upgrades?

nate.the.great's awesome what fits what post

How do I install springs/struts/coilovers?

Refer to the manufacturer's instructions. For items without instructions, below is a link to some of the better known installation instructions:

Scoobymods.com instructions

What should I do after the installation of struts/springs/coilovers?

Always, always, always get an alignment! Wait a few days or up to a week for the suspension to "settle" in nice and tight. Then follow the above listed steps to get a proper alignment. No matter how careful you were with your installation, you should NEVER swap out major suspension components without getting an alignment. More than one person has taken this shortcut only to realize they need new tires due to horrible wear within two weeks.

Editors Note

This post was created by the prompting and urging of my good forum buddy ButtDyno, and the support of many, many suspension smart people. I came up with the text based on LOTS of searching here. It was also created to be intentionally brand neutral so that it serves as a stepping stone for further research. Upon reading this you should have an idea of what type of springs/struts/coilovers best suit your needs. The manufacturer is up to you.

If you find an error in this FAQ, please PM me with factual details and I will update this post. Responses such as, "I have XXX's springs and they are great!" or "XXX's struts leaked after 1 month" are not appreciated here, that is what the Car Parts Review Forum is for.