Sway Bar Kit Rear 25MM STI
PSP-SUS-207
Turn harder and flatter with 25mm power from PERRIN! Subaru STI 2004, 2005, 2006, and 2007
Install Difficulty Rating
The only way to make your car turn, stop or go is if all the available tire patch is hitting the surface at hand. The factory included what many regard to be a whimsical attempt to increase cornering with puny sway bars on the front and rear. PERRIN™ sees the need for a far larger and stronger sway bars and now offers two choices for both ends of your car.
The only way to make your car turn, stop or go is if the entire available tire patch is hitting the surface at hand. The factory included what many regard to be a whimsical attempt to increase cornering with puny sway bars on the front and rear. PERRIN™ sees the need for far larger and stronger sway bars and now offers two choices for the rear end of your car.
For street enthusiasts that simply want to attack the drive to work with more gusto, the 22mm (7/8”) PERRIN swaybar kit is the ideal choice. While dedicated track hounds will delight in the increased snap now available from our 25mm (1”) offering. Each size and each end also incorporates 2adjustment holes to help you custom tailor your suspension to your specific needs and driving habits. Made from solid steel and heavily powder coated to prevent the rigors of salty roads that wreck havoc with less worthy products. All kits include polyurethane pocketed bushings to prevent tedious re-greasing and all necessary hardware fora clean, and painless installation.
Stout Mounts
All PERRIN swaybar kits include the Stout-Mount™ system. This is another factory flaw. The Stout Mounts area connection between the unibody and the rear sway bar. Subaru chose to use cheap stamped steel. While great to keep costs down it certainly won’t help you go around that next bend in anything resembling a spirited fashion. Impreza owners can take full advantage of the 6061billet aluminum mounts. These mounts are overbuilt to handle the added stiffness of upgraded swaybars. You will never have to worry about these failing
Endlinks
Also any rear sway bar and swaybar kit can be purchased with or with out our endlinks. PERRIN™ recommends the use of upgraded endlinks to take full advantageof any swaybar upgrade. Endlinks are the connection between the swaybar and the suspension arms. Some Subaru models use plastic (yesplastic) to make this connection, where as the Legacy uses a solid type connection. So why replace it? The OEM steel endlinks are designed to hold up under the stresses of the OEM bar, not upgraded swaybars. Replacing these with PERRIN solid endlinks will add to the durability and save you some weight at the same time. PERRIN™ Endlinks are made from 6061 billet aluminum and use spherical bearings. This provides a solid non-flexible connection from the sway bar to the control arms.
Want to learn how to install this product? Click here for instructions!
Look under your STI. Go ahead, we’ll wait…. See that little sway bardown there? Replace it with a PERRIN Performance sway bar and wepromise better cornering, reduced body role and greater control overyour suspension. PERRIN Performance™ Sway Bars are bigger in diameterand come with multiple end-link attachments, giving you 3 possibleconfigurations.
How does a sway bar work?
First understand that a tire hasflat contact patch. If the contact patch is not parallel to theground, the contact patch gets smaller. In turn traction is lost. Asthe car makes its way through a turn, the weight of the car, causes thecar to lean. As the car leans, the design of the suspension geometrymakes the tires contact patch become unparallel to the ground. In turnloosing traction.
Suspension designers used camber to help counteract this, along withunequal control arms. But a large part of keeping the tire parallel tothe ground during cornering is controlling how much the car leans. This is where sway bars come into play. During cornering the sway baracts to keep the chassis from leaning. In turn this helps keep thetires parallel to the ground. Stiffening up the springs on the cardoes the same thing, but in turn makes the ride much harsher. Swaybars are like stiff springs but only become effective while cornering.
Swaybars connect both left and right control arms with a torsion bar.As the control arms move up and down together, the bar moves withthem. During this state the sway bar has no effect. Only when thecontrol arms move in opposite directions does the sway bar come intoplay. During a corner, the outside arm moves up and the inside armmoves down, in turn causing the sway bar to twist. The opposingdirections of the arms are counteracted by the sway bar and the swaybar tries to keep the arms from moving in opposite directions. In turnkeeps the car from leaning less, and give you more traction!
Why do I want this?
That is easy to keep the contact patch asflat to the ground as possible! Both front and rear sway bars dodifferent things to cars. Both front and rear sway bars increasetraction to the outside tire (the one with the most load), but abalance of front to rear can change how the car handles.
All cars are designed to have a slight amount of understeer. This isdone for safety reasons. Understeer is the effect when you go into acorner, and your turn the wheel, but the car goes straight. This isalso known as pushing or plowing. In contrast oversteer is when you gointo a corner, and the car turns more than you steer. This is alsodescribed as the rear end feeling like it is sliding out slightly. Toomuch oversteer and you will spin out in a corner. Too much understeerand the car will not turn through the corner, and go straight off theroad.
Generally people prefer neutral handling or a slight amount ofoversteer. With the choices in bar sizes and endlink settings, anyonecan find the perfect match to their driving style.
Hollow vs. Solid
Given both are designed to produce the samerate or stiffness, they both do the same job. But in order to get ahollow bar to produce the same rate, a very large diameter is needed.And for those wanting something with a high rate or stiffness, youwon’t be able to find this in a hollow bar. Another benefit hollow barmakers try to sell is the weight. The difference in weight is veryvery small. To give an example, a rear WRX PERRIN sway bar weighs10.8lbs. Even if you remove the entire bar, the savings isn’t much. If weight is that critical, you can always remove your spare and savemore weight. All PERRIN sway bars are made with solid 4140 Steel bar.This provides the best in both stiffness and durability, and creates abar that will last forever.
Sway bar Settings
All PERRIN swaybars comes with multiple endlink connections. Thisallows the end user to customize the stiffness of the bar. All PERRINswaybars come with at minimum 2 settings. These 2 settings can provide3 actual different setting with crossing the endlink connections. Our3 setting swaybars can provide 5 different setting by doing the samething. Below are some basic calculations of % change from OEM toPERRIN 22mm and 25mm bars. The crossed endlink calculations are notmentioned below, but can be figured as they will fall in between therates mentioned. The sway bar settings can allow for significantchanges in sway bar functionality, with out having to go buy anothersize bar.
STI SWAY BAR % INCREASE BASE ON DIAMETER ALONE
Stock Diameter PERRIN Sway bar % Increase
19mm 22mm 180%
19mm 25mm 319%
OEM 19mm BAR ONLY SETTING
EFFECTIVE RATE 150 LBS/IN
PERRIN 22mm BAR SETTING #1 BAR SETTING #2
EFFECTIVE RATE 285 LBS/IN 360 LBS/IN
RATE INCREASE OVER STOCK 185% 235%
PERRIN 25mm BAR SETTING #1 BAR SETTING #2
EFFECTIVE RATE 485 LBS/IN 610 LBS/IN
RATE INCREASE OVER STOCK 315% 400%
Bushings
All PERRIN swaybars use custom made polyurethane bushings. We wentdirect to the experts on this and that is why you will find 100%genuine Energy Suspension bushings. All of our bushings use a highdurometer (really stiff) urethane to ensure the most from your swaybar. A common problem with urethane bushings is the squeak really badwhen the grease dries up. PERRIN performance has custom internalspiral cores for each bushing. This allows the grease to stay in thebushings, and constantly lube the sway bar. In turn this makes forlonger service intervals compared to traditional smooth bushings. Thisis a small detail that other sway bar manufactures don’t offer!
PERRIN 25mm Rear Swaybar
PERRIN Stout Mounts
Energy Suspension Bushings and grease
Fits all Subaru Impreza 1993-2007 (with OEM RSB)
May interfere with some non-PERRIN, non-OEM endlinks. See customerservice for more details, or consult the installation instructionsincluded with your kit.
Sway bar Settings
All PERRIN swaybars comes with multiple endlink connections. Thisallows the end user to customize the stiffness of the bar. All PERRINswaybars come with at minimum 2 settings. These 2 settings can provide3 actual different setting with crossing the endlink connections. Our3 setting swaybars can provide 5 different setting by doing the samething. Below are some basic calculations of % change from OEM toPERRIN 22mm and 25mm bars. The crossed endlink calculations are notmentioned below, but can be figured as they will fall in between therates mentioned. The sway bar settings can allow for significantchanges in sway bar functionality, with out having to go buy anothersize bar.
STI SWAY BAR % INCREASE BASE ON DIAMETER ALONE
Stock Diameter PERRIN Sway bar % Increase
19mm 22mm 180%
19mm 25mm 319%
OEM 19mm BAR ONLY SETTING
EFFECTIVE RATE 150 LBS/IN
PERRIN 22mm BAR SETTING #1 BAR SETTING #2
EFFECTIVE RATE 285 LBS/IN 360 LBS/IN
RATE INCREASE OVER STOCK 185% 235%
PERRIN 25mm BAR SETTING #1 BAR SETTING #2
EFFECTIVE RATE 485 LBS/IN 610 LBS/IN
RATE INCREASE OVER STOCK 315% 400%
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