What Is an Alignment Shim?

Alignment shims are a set of special tools used in the wheel alignment process to make precise adjustments. Tire mechanics use them to correct alignment angles, such as camber, caster, and toe, to manufacturer specifications. Shims are particularly useful for vehicles with non-adjustable suspensions or fine-tuning alignment on any vehicle.

How Do Alignment Shims Work?

Technicians place alignment shims between the suspension and chassis components of a vehicle to adjust the wheel alignment angles—camber, caster, and toe—to their correct specifications. They are thin, flat pieces of metal or plastic that can be stacked or removed to change the alignment incrementally.

By altering the spacing, shims fine-tune the wheel position, which is critical for vehicles that lack built-in adjustment features. They also assist in achieving precise alignment settings necessary for optimal tire wear and vehicle handling.

How Are Alignment Shims Made?

Manufacturers typically fabricate alignment shims from a variety of materials, including stainless steel, aluminum, or plastic. They cut these shims to various thicknesses and dimensions to suit the alignment needs of different vehicles and machinery. The process could include stamping, cutting, and finishing to achieve the precise size and shape needed for proper alignment adjustment.

Why Use Alignment Shims?

Modern vehicles often come with limited alignment adjustment capabilities. As the vehicle ages and components settle, alignment can drift out of specification, leading to premature tire wear and handling issues. Shims provide a solution for these limited adjustments and restore proper alignment.

What Is Rear Alignment Shim?

Rear alignment shims are used to adjust the toe angles on vehicles where these parameters may be out of the factory specification. They are suitable for certain vehicles with adjustable A-arms or on some beam-style rear suspensions with a fixed angle at the hub.

Difference Between Front Shim and Rear Shim

The front shim is larger and has a square cutout area in the center to clear the wheel speed sensor. While rear shim is smaller and does not have a square cutout area in the center.

How Much Does Alignment Shim Cost?

A single Specialty Products alignment shim is approximately $13​​. On Amazon, you can find a kit of 144 pieces of various sizes for around $12.99, which is quite economical for a bulk assortment.

For more specialized applications, such as heavy-duty truck alignment shim assortments, prices can go up significantly, with a set costing $455. Meanwhile, individual shims can range from as low as $5.29 to around $28.49, depending on the specific type and vehicle compatibility.

Shims for Modified Vehicles

Vehicles modified with lift kits or lowering springs may require additional alignment adjustments. Aftermarket problem-solver kits, which include cam bolts, shims, and adjustable links, can offer increased adjustability for such modifications. They ensure that the vehicle maintains proper alignment.