SuperPro DURO4428K DuroBall Front LCA Inner Rear Bushing Kit Double Offset Caster

The SuperPro DURO4428K is a DuroBall front lower control arm (LCA) inner rear bushing kit featuring a double offset design for additional positive caster correction. Engineered for the Subaru VA WRX and STI, this kit provides a measurable suspension geometry upgrade delivering approximately 1.5 degrees of additional caster to both sides of the vehicle.

DuroBall Technology:

• Hybrid metal-polyurethane construction — a unique combination of SuperPro's engineering-grade polyurethane with a specialized metal spherical bearing for demanding performance applications
• Isolated spherical bearing design — delivers the precision and articulation of a full bearing assembly while retaining the NVH (noise, vibration, and harshness) mitigation of SuperPro's bespoke polyurethane formulation
• Superior to traditional elastomer bushings — provides greater positive location, stiffer response, and no compromise in articulation compared to OEM rubber bushings

Double Offset Caster Benefits:

• Improved straight-line stability and tracking — the vehicle will track true and return to center with less driver input
• Dynamic camber gain with steering angle — maximizes the tire contact patch as suspension loads up through corners, improving grip and resisting tire roll-onto-the-shoulder
• Enhanced steering weight and feel — adds natural on-center steering weight and improves feel at the handling limit
• No negative impact on tire wear, comfort, or handling behavior — a geometry improvement with no drawbacks
• Axle alignment required after installation

About SuperPro: SuperPro is an Australian suspension specialist with nearly five decades of development experience. Their polyurethane bushings are engineered to maintain OEM levels of noise and harshness isolation while delivering measurably superior performance across all conditions.