How Brake Shims Work

Brake Pad With ShimBrake shims are the automanufactuer’s best tool for fighting brake noise. Without them, the individual parts of the brake would cause all kinds of vibration and noise. This article offers an in-depth look at brake shims, and how to install them.

Brake Shims

How They Work

Brake shims prevent and reduce the transmission and amplitude of vibrational forces. This is achieved with dampening material bonded to the pad assembly. Shims also add mass to the brake that can dampen vibrations in the pad and caliper. Shims can act as a thermal barrier to ensure consistent temperatures across the pad, which gives consistent brake torque. High quality brake shims are multilayered with varying grades of dampening materials. Engineers tune these layers to get the best NVH qualities for that specific brake system. If the shim is not making contact with the brake pad, it will not do its job.

Two Piece Shim

Shim Installation

Before installing any brake pad or shim, take time to look it over. Some of the best brake pads already have the insulator attached to it. This ensures effectiveness in three ways. First, it prevents the technician from forgetting to install it. Second, a heated press can be used to properly cure the adhesives, and third, the manufacturer can test the shim to make sure it performs correctly. If the shim isn’t already attached, you can drop it on a hard surface to see how well it absorbs vibrations. If a set of pads doesn’t look “right,” don’t install them. It’s easier to return opened but unused pads rather than used ones. It’s easy to blame the pads when experiencing a comeback due to brake noise, but the sound the customer is hearing isn’t just the brake pads, it’s a product of the entire brake system which is why it’s important to look at the entire brake system when diagnosing brake noise.