Perrin Performance - POSITIVE STEERING RESPONSE SYSTEM FOR 2002-07 WRX/STI
P.S.R.S stands for Positive Steering Response System and simply replaces the front control arm rear bushings. The OEM bushings are designed to be extra compliant to reduce NVH, and make the ride more comfortable. The compliancy of this bushing is not something a performance oriented driver is looking for. Eliminating the OEM super soft bushing provides significant improvement in how the car steers during hard cornering and even in a straight line
Under braking and acceleration, the OEM bushing can flex enough for your wheel to move back and forth .500"! This deflection of the wheel causes drastic toe in and toe out changes under braking. The toe changes will cause steering wandering and an altered tire contact patch. When accelerating, this OEM bushing causes unwanted wheel hop and the car will want to follow the ruts in the road.
After the PERRIN PSRS is installed, under braking the wheel will have zero deflection. Since there is no way for toe changes to occur, the steering feedback issues and wandering under braking disappears. Under acceleration the car will have far less tendency to follow the ruts in the road, wheel hop will be eliminated, and in turn the car will have more front-end traction.
The bushing in the PSRS is purposely offset from center-line. This adds approximately 0.5 degrees of caster to the front suspension. Caster is the angle on which the steering knuckle rotates. Adding caster makes the car turn in faster by providing a larger contact patch as the wheels turn on the steering axis.
A byproduct of the PSRS kit is that it reduces some of the built in "anti-lift" that Subaru builds into the suspension geometry. Changing the geometry toward a Pro-Lift setup which means there is more weight transfer happening under acceleration and deceleration. During acceleration this helps transfer weight to the rear of the car creating additional traction for the front tires, which reduces understeer. Same thing happens under braking.
The PERRIN PSRS features custom made Polyurethane Bushings. We choose a stiff 95a durometer material to provide a feel similar to a solid bearing bushing but without the harshness or noise that can be associated with them after years of use. Polyurethane is extremely durable, nearly maintenance free and less expensive than bearing type bushings. PERRIN polyurethane PSRS's were designed for those living in climates where your vehicle is commonly exposed to corrosive elements. The combination of aluminum, polyurethane, and yellow zinc plated hardware make PERRIN performance PSRS's very weather resistant and unaffected by wet climates and road salt. Polyurethan bushings will also transmit slightly less noise through the chassis than more rigid mediums.
The PSRS uses Zerk grease fittings to feed lubricant to the joint without the need to disassemble the PSRS. Grab your grease gun, and grease away!