Perrin Sway Bar Rear 08+ WRX/STi 19mm

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 both ends of your car.

For street enthusiasts that simply want to attack the drive to work with more gusto, the 19mm upgrade is the ideal choice. While dedicated track hounds will delight in the increased snap now available from our 22mm offering. Each size and each end also incorporates 3 adjustment 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 for a clean, and painless installation.

Look under your WRX. Go ahead, we’ll wait…. See that little sway bar down there? Replace it with a PERRIN Performance sway bar and we promise better cornering, reduced body role and greater control over your suspension. PERRIN Performance™ Sway Bars are bigger in diameter and come with multiple end-link attachments, giving you 5 possible configurations.

How does a sway bar work?

First understand that a tire has flat contact patch. If the contact patch is not parallel to the ground, the contact patch gets smaller. In turn traction is lost. As the car makes its way through a turn, the weight of the car, causes the car to lean. As the car leans, the design of the suspension geometry makes the tires contact patch become unparallel to the ground. In turn loosing traction.

Suspension designers used camber to help counteract this, along with unequal control arms. But a large part of keeping the tire parallel to the ground during cornering is controlling how much the car leans. This is where sway bars come into play. During cornering the sway bar acts to keep the chassis from leaning. In turn this helps keep the tires parallel to the ground. Stiffening up the springs on the car does the same thing, but in turn makes the ride much harsher. Sway bars 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 with them. During this state the sway bar has no effect. Only when the control arms move in opposite directions does the sway bar come into play. During a corner, the outside arm moves up and the inside arm moves down, in turn causing the sway bar to twist. The opposing directions of the arms are counteracted by the sway bar and the sway bar tries to keep the arms from moving in opposite directions. In turn keeps the car from leaning less, and give you more traction!

Why do I want this?

That is easy to keep the contact patch as flat to the ground as possible! Both front and rear sway bars do different things to cars. Both front and rear sway bars increase traction to the outside tire (the one with the most load), but a balance of front to rear can change how the car handles.

All cars are designed to have a slight amount of understeer. This is done for safety reasons. Understeer is the effect when you go into a corner, and your turn the wheel, but the car goes straight. This is also known as pushing or plowing. In contrast Oversteer is when you go into a corner, and the car turns more than you steer. This is also described as the rear end feeling like it is sliding out slightly. Too much oversteer and you will spin out in a corner. Too much understeer and the car will not turn through the corner, and go straight off the road.

Generally people prefer neutral handling or a slight amount of oversteer. With the choices in bar sizes and endlink settings, anyone can find the perfect match to their driving style.

Hollow vs. Solid

Given both are designed to produce the same rate or stiffness, they both do the same job. But in order to get a hollow bar to produce the same rate, a very large diameter is needed. And for those wanting something with a high rate or stiffness, you won’t be able to find this in a hollow bar. Another benefit hollow bar makers try to sell is the weight. The difference in weight is very very small. To give an example, a rear WRX PERRIN sway bar weighs 10.8lbs. Even if you remove the entire bar, the savings isn’t much. If weight is that critical, you can always remove your spare and save more weight. All PERRIN sway bars are made with solid 4140 Steel bar. This provides the best in both stiffness and durability, and creates a bar that will last forever.

Sway bar Settings

All PERRIN swaybars comes with multiple endlink connections. This allows the end user to customize the stiffness of the bar. All PERRIN swaybars come with at minimum 2 settings. These 2 settings can provide 3 actual different setting with crossing the endlink connections. Our 3 setting swaybars can provide 5 different setting by doing the same thing. Below are some basic calculations of % change from OEM to PERRIN 19mm and 22mm bars. The crossed endlink calculations are not mentioned below, but can be figured as they will fall in between the rates mentioned. The sway bar settings can allow for significant changes in sway bar functionality, with out having to go buy another size bar.