Leaf Spring Shim Kit
Skyjacker Suspension WSC60 6 Degree Contoured Leaf Spring Axle Shim 2.5 Inch Wide
What Is a Leaf Spring Shim Kit?
A leaf spring shim kit is a small but critical suspension component used on trucks, SUVs, and off-road vehicles with solid-axle, leaf spring suspension setups. These precision-machined wedges are placed between the leaf spring pack and the axle housing to correct the pinion angle, adjust ride height, or level a vehicle that leans to one side. While they may look simple, getting these angles right has a direct impact on drivetrain longevity, handling, and on-road safety.
Why Pinion Angle Matters
When you install a suspension lift kit, the relationship between the driveshaft, differential pinion, and axle changes significantly. A misaligned pinion angle can introduce driveline vibration that accelerates wear on U-joints, the transmission, and the transfer case. Leaf spring shim kits provide a targeted, non-invasive correction — inserting the right degree shim restores proper geometry without cutting, welding, or moving spring perches.
Beyond pinion angle, shims are also used to fine-tune ride height and correct side-to-side lean. Many trucks leave the factory with a slight lean due to fuel tank placement, driver weight bias, or spring tolerances. A shim placed between the leaf pack and axle pad on the lower side can quickly restore a level stance.
Key Features to Consider When Shopping
- Degree angle: Shims are commonly available in 2°, 2.5°, 3°, 4°, and 6° increments. Measure your current pinion angle before selecting a shim to ensure you correct — not overcorrect — the geometry.
- Width compatibility: Match the shim width to your leaf spring pack width (commonly 2.5" or 3"). Using an incorrectly sized shim can create instability at the axle pad.
- Spring-over or spring-under: Whether your springs run over or under the axle determines whether you need a flat or contoured shim style.
- Material: Most quality shims are machined from aluminum alloy. Avoid thin or soft materials that may deform under load.
- Center pin hole: Look for pre-drilled center pin holes so the shim stays properly located within the spring pack.
Top Brands in Leaf Spring Shim Kits
Skyjacker Suspension is one of the most recognized names in the leaf spring shim market. Their shims are made from high-quality aluminum and are available in both flat and contoured styles to accommodate springs mounted over or under the axle — making them a versatile choice across a wide range of lift configurations for Chevy/GMC, Dodge, Ford, Jeep, and Toyota platforms.
Rancho Suspension brings decades of off-road engineering expertise to their leaf spring shim lineup. Their popular RS8125 kit is a universal-fit solution designed to work with most aftermarket lift installations, offering a durable aluminum construction and a limited warranty that gives DIY installers confidence.
Rubicon Express is a brand built specifically around Jeep performance, and their leaf spring shim kits reflect that focused expertise. Their steel degree shims are a go-to solution in the Jeep community for correcting caster and pinion angle after shackle lifts and spring swaps — a particularly common need on YJ and TJ Wranglers.
Installation Tips
Leaf spring shim installation is a straightforward job for an experienced DIYer, but always measure your driveline angles before and after with a digital angle gauge. After installation, have your caster and alignment checked at a shop to ensure your steering geometry is within spec. Proper angle correction not only extends the life of your U-joints and driveshaft — it makes your truck or Jeep noticeably smoother on the highway.