Eric the Car Guy was one of the first YouTube automotive celebrities. In 2010, Eric came across a car where the shim was separated from the brake pad and made contact with the hat of the rotor.
The brake shim failed because the adhesive holding it to the brake pad failed and it was not mechanically attached. Also, the adhesive failed because the paint was compromised by corrosion.
Fast forward to 2015, when Bosch recalled more than 50,000 brake pad sets because the shims would move out of position and come in contact with the rotor and cause it to fracture.
Eric’s follow up to his 2010 video covers the importance of selecting brake pads that have a high-quality brake shim that is held to the backing plate using mechanical attachment methods like clips.