A-Arm Caster Slug 3/8in

The A-Arm Caster Slug 3/8in is a precision alignment component designed for front-end suspension geometry correction on street, strip, and road-course vehicles. This caster adjustment slug is engineered for mechanics and suspension builders who need to dial in proper caster angle without replacing entire control arm assemblies. Whether you're recovering lost caster from lowering springs, fine-tuning handling characteristics, or restoring factory alignment specs, the 3/8-inch diameter slug threads into standard A-arm mounting holes to shift the steering axis inclination angle and improve directional stability and tire wear patterns.

Constructed from hardened steel and finished to withstand repeated adjustment cycles, this caster slug features a 3/8-inch nominal diameter that accommodates most bolt-in A-arm configurations. The compact 3.5-inch length and lightweight design (0.06 lbs) make installation straightforward—no frame modification or custom machining required. By inserting the slug between the A-arm and frame or chassis bushing, you shift the pivot point slightly, increasing or decreasing caster as needed. This method delivers repeatable, measurable results without requiring full suspension teardown, making it ideal for quick alignment corrections between dyno runs or track sessions.

Mechanics working on independent front suspension systems—especially those running lowered or modified geometry—will find this slug invaluable for restoring positive caster and eliminating bump-steer symptoms. It works with most double-wishbone and A-arm designs where bushing thickness adjustment is practical. Proper caster angle reduces steering effort while improving straight-line tracking and cornering response. Installation requires no specialized tools; simply remove the control arm bolt, insert the slug, and reinstall hardware to specification. Always verify alignment with a professional alignment rack after adjustment to ensure all angles meet your vehicle's target specs.