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It is necessary to consider both pad stiffness in static and dynamic situations to develop brake pads that create effective braking and squeal less. Brake pads that have a high degree of static stiffness generally respond well when braking. A past study clarified that stiffness when vibration is added to a pad differs from static stiffness. This pad stiffness in dynamic situations depends on braking pressure and it is one of the causes of squeal generation. This research clarified that pad stiffness depends on the amplitude of excitation and its frequency, which was measured by using an experimental apparatus. This apparatus gave sufficient displacement to a pad for measuring static stiffness and gave vibration with sufficient frequency and amplitude to assess the stiffness of the pad when squeal was generated. First, the static stiffness of the pad was measured by adding static pressure.

The prevention of brake squeal in disc brakes is an important concern in designing a brake system because, in terms of quietness, brake squeal reduces a car's commercial value. Over the past years, many studies have been conducted to elucidate the mechanism underlying the occurrence of brake squeal. However, since disc brake squeal is a complex issue caused by the compound influence of friction phenomena and vibrations in the brake system, the problem of brake squeal still has not been completely resolved, even today. In order to propose an effective measure for the prevention of brake squeal, it is necessary to understand the nature of the brake squeal phenomenon. We have investigated the influence of the dynamic stiffness of a brake pad (hereinafter referred to as pad stiffness). The pad stiffness was evaluated the results by a pad excitation at frequencies and vibration amplitudes that would cause brake squeal.