Brake shims are thin metal or rubber adhesive pads that fit between the brake pad and the brake caliper to correct small differences that sometimes lead to noise. On most of the newer cars, these brake shims are mainly used to keep the noise down and any rattles to a minimum. Not all brake pads come with shims as they aren't required and function perfectly without needing them.
It is often misdiagnosed that the brake rotors themselves are the cause of excessive brake noise such as squeaking or squealing when using moderate brake pedal pressure. While we will save another dedicated article for all the possible causes and solutions, it is very common that the lack of brake shims is often the main reason for brake noise.
Brake pad shims come in a variety of styles to suit your driving style. For brake pads that did not come with any shims, we carry an application that you can apply to your non-shimmed brake pads to receive the same benefits of using brake pad shims. It's also recommended to apply a thin layer between the backing plate and the shim even if the shim is present, as it will prevent any further noise from the pad rattling against the shim.
There are also brake pads that will come with adhesive brake pad shims that require you stick on the shim to the brake pad backing plate. This doesn't require the use of disc brake lube, but you can still apply a thin coating on top of the brake backing plate. Lastly, there are also titanium brake pad shims which act as an improved thermal barrier. These are used for track use only as they reflect more heat than regular shims do. This results in less heat transfer from the pads to the caliper, lowering hydraulic fluid temperatures (brake fluid).