UMI Performance 2039-B Adjustable Rear Lower Control Arms with Roto-Joints

The UMI Performance 2039-B adjustable rear lower control arms deliver professional-grade suspension performance with on-car adjustability for GM muscle cars and performance vehicles. These control arms feature UMI's proprietary Roto-Joint technology combined with polyurethane bushings to provide bind-free suspension articulation while maintaining excellent street manners and ride quality.

Key Features:

• Constructed from 1.250" x 0.120" DOM mild steel tubing with TIG welded 4140 chromoly tube adapters for maximum strength
• On-car adjustable design using heat-treated chromoly adjusters allows you to fine-tune rear axle position
• UMI Roto-Joints provide 28 degrees of unrestricted rotational movement with greaseable, rebuildable delrin race construction
• Polyurethane bushings on chassis end absorb road noise and vibration for comfortable street driving
• Durable powder coat finish resists corrosion and maintains appearance
• Ships fully assembled and ready to install using OEM hardware
• Greaseable design ensures low maintenance and long service life

Roto-Joint Technology:

UMI's exclusive Roto-Joint (Rotational Joint) combines the precision of a spherical rod end with the street-friendly characteristics of a bushing. The hard chrome plated 4140 chromoly ball rotates within a CNC-machined delrin race, allowing the suspension to articulate correctly without bind. This design eliminates deflection found in rubber and polyurethane bushings, improving traction and significantly reducing wheel hop during hard acceleration.

Adjustability Benefits:

The on-car adjustable feature allows you to lengthen or shorten the control arms to move the rear axle forward or backward. This is essential for fitting larger tires, centering aftermarket rear axle assemblies, and preventing tire rubbing issues. Adjustment can be performed without removing the control arms from the vehicle.

Hybrid Bushing Design:

This set features a hybrid configuration optimized for street performance: polyurethane bushings mount to the chassis side to filter road shock and noise, while Roto-Joints attach to the axle side to provide precision handling and bind-free articulation. This combination delivers the best of both worlds for street enthusiasts and performance drivers.

Optional Upgrades:

Chrome moly construction available using 1.250" x 0.095" wall 4130 chromoly steel for increased strength with reduced weight. Optional spanner wrench tool available for adjusting Roto-Joint tension and performing maintenance or rebuilding as needed over time.