Why does the factory radius arm fail under limit conditions?

The OEM arm is a steel casting equipped with a massive rubber bushing on the chassis side. Its primary role in a stock car is to dampen vibrations and ensure daily driving comfort. However, under hard braking or through high-speed sweepers, this rubber becomes a “living,” unpredictable element of the system. Under longitudinal forces, it undergoes significant compression (deflection), allowing the wheel to shift within the wheel well. The driver feels this as front-end “floating,” a lack of turn-in precision, and the need for constant steering corrections to maintain the intended line.

RST Engineering: T651 Aluminum and Uniball Technology

When designing this arm, we rejected rubber and stamped steel in favor of pure mechanical performance:

• CNC Billet T651 Aluminum. The main arm body and mounting blocks are CNC machined from solid blocks of aircraft-grade T651 aluminum alloy. Choosing this material guarantees extreme structural rigidity while simultaneously reducing unsprung mass. The multi-component design allows for precise adjustments that are simply unattainable with factory parts.

• Spherical Bearings (Uniball) on both ends. This is the key to surgical precision. We have completely eliminated rubber:

  • Chassis side: A high-performance spherical bearing housed in a custom aluminum mount eliminates longitudinal deflection to zero.

  • Knuckle side: An integrated Heavy-Duty spherical bearing replaces the standard ball joint, ensuring smooth suspension operation throughout its full travel with zero delay.

The Result: A New Definition of Control

The RST Tension Link is designed for those who want to “read” the road through their fingertips on the steering wheel. We transform the vague, rubbery, and delayed front-end reactions of the Mustang into instantaneous feedback. It is the essential foundation for anyone building a precision track weapon or simply demanding flawless handling from their daily-driven machine.