SPC Performance Alignment Caster Shim Kit

SPC Performance Alignment Caster Shim Kits: Precision Caster Correction from the Industry Leaders

When caster angles drift out of spec — whether from a suspension lift, worn components, or a factory geometry that simply needs dialing in — a quality shim kit is often the most direct and cost-effective fix available. SPC Performance (Specialty Products Company) has been engineering alignment solutions since 1971, and their alignment caster shim kits represent decades of real-world refinement from a brand that professional alignment technicians and performance enthusiasts have trusted for generations.

Why Caster Matters — and Why Shims Work

Caster angle — the forward or rearward tilt of the steering axis — has a direct impact on straight-line stability, steering returnability, and overall handling feel. Even a small deviation from the correct spec can cause a vehicle to pull to one side, wear tires unevenly, or feel vague and unresponsive. Caster shim kits correct this angle by inserting precisely angled shims between suspension components and the chassis, nudging caster back into spec without requiring expensive new hardware.

SPC's caster/camber shims provide positive caster changes on vehicles by installing them between specific suspension components or the chassis, and they are stackable for larger changes. This stackable design gives technicians and DIYers a flexible, scalable correction method — a single kit can address a mild deviation, and stacking shims accommodates more aggressive lifts or geometry corrections.

Application Coverage Across a Wide Range of Vehicles

Specialty Products Company is the world leader in the development, manufacturing, and sales of wheel alignment parts, with SPC Performance targeting the off-road, track, and enthusiast markets — and their caster shim kit lineup reflects that breadth. The range covers solid axle rear-wheel-drive and four-wheel-drive trucks, popular Jeep platforms like the Cherokee (XJ), Wagoneer, Comanche (MJ), and Grand Cherokee (ZJ), as well as over-the-road trucks and trailers. Individual kits can change caster positive or negative from 1/2 degree to 4 degrees, and are applicable to any solid axle RWD or 4WD vehicle.

For Jeep-specific applications, these shims provide positive caster changes on early model downsized Jeeps by installing them between the lower control arm and the frame bracket, and are stackable for larger changes. Kits typically include multiple shims per package, giving installers everything needed to complete both sides of the vehicle in a single purchase.

Built by Alignment Specialists, Validated in Competition

Specialty Products Company has been an industry leader in automotive alignment solutions for decades, with alignment tools and components trusted by mechanics, off-roaders, and performance enthusiasts worldwide — founded in 1971, SPC has revolutionized vehicle alignment with innovative alignment tools made for precise alignment tuning. That heritage carries directly into their shim kit line. Motorsports can be hard on suspension components, and SPC components are race-proven, enduring the harsh environment that only competition can provide — if parts can survive that torture, they are up to the task for daily driven commuter vehicles.

SPC tools and components are designed and tested in the USA, ensuring long-lasting reliability and accuracy. For the installer, that means confidence in the shim angle consistency and material durability across thousands of service cycles.

The Right Kit for Street, Off-Road, and Everything Between

SPC now provides solutions for lifted trucks, lowered vehicles, classic and modern muscle cars, as well as dedicated racing applications and more. Whether you are correcting caster on a daily driver after a two-inch leveling kit, restoring factory geometry on a classic 4x4, or fine-tuning a competition build, SPC's caster shim kits offer a vehicle-specific, engineered solution backed by one of the most recognized names in alignment. Browse the full alignment caster shim kit category or explore the complete SPC Performance product lineup to find the right alignment solution for your application.