Analysis of Automotive Braking Noise (Brake Pad Chapter)

Types of braking noise：

1.Low frequency noise

A dull trembling sound. Frequency below 300Hz

 

Reason: The brake disc jumps too much on the wheel hub.

 

The flat runout of the brake disc exceeds the requirement.

 

The installation quality of the brake disc on the wheel hub is poor.

 

2.Intermediate frequency noise

 

Long scream. Frequency 300Hz~5000Hz

 

Reason: The caliper is stuck.

 

The brake pads cannot move properly in the caliper.

 

Brake disc wear exceeds the minimum thickness.

 

Scratches on the surface of the brake disc.

 

Because the brake design of the specific vehicle model has already been finalized, the impact of brake design on braking noise will not be considered here. The causes of brake noise are analyzed solely from the performance parameters of the brake pads. This issue analyzes the product reasons - friction materials and production processes.

Factors Causing Braking Noise：

From the perspective of friction materials, the factors are roughly as follows:

 

① The higher the friction coefficient of the friction material, the more likely it is to generate noise

 

② The material hardness of the brake friction pair is high, which is prone to noise generation.

 

③ High hardness fillers are prone to noise when used in large quantities

 

④ After high-temperature braking, the working surface of the brake pads forms a bright and hard carbonized film, also known as an enamel layer. During braking friction, high-frequency vibration and corresponding noise are generated.

 

From the perspective of production technology, the factors are roughly as follows:

 

① Uneven mixing during mixing (besides noise, it can also cause some degree of disc damage)

 

② Sheet size tolerance out of tolerance (for new parts)

 

③ Product deformation caused by accidents

 

Factors that cause vibration in brake discs：

① Changes in the disc

 

② Hardness tolerance

 

③ Brake vibration

 

④ Thermal variation of the disc