SAE J2786:2017 pdf free

SAE J2786:2017 pdf free.Automotive Brake Noise and Vibration Standard Nomenclature
The general definition for brake squeal is an audible noise radiating from the brake system components. The brake squeal heard coming from a given brake corner of the vehicle normally is a fixed frequency or single pure tone; however in some instances, it may contain higher order harmonics of this frequency. The brake squeal frequency typically ranges from 900Hz to 17 kHz. Under variations in brake stopping parameters (such as temperature, pressure, speed,deceleration), the frequency of the brake squeal can jump to a different frequency. According to theory, the specific allowable squeal frequencies are controlled by the resonant modes of the brake components. Brake squeals can exhibit a wide range of variation in time duration or where the noise occurs during the stop. The following definitions can help to further describe particular types of squeals in terms of their frequency content and when the noise occurs during the stop.
The groan heard during a dynamic stop; it usually is more pronounced during a moderate to a higher deceleration and when slowing through the 30 to 10 km/h range. A certain preconditioning stop sequence is usually required to create the noise. For instance, it may require doing stops to heat the brake above a certain temperature and then waiting for the brake to cool down a bit before getting the groan to happen. The conditioning sequence can vary significantly from one vehicle setup to another. Sometimes the groan spectrum will contain a component that decreases in frequency with vehicle speed (and appears related to a high order of wheel speed, such as number of vanes/channels in the rotor).
This groan happens on vehicles equipped with automatic transmissions. When the vehicle is stopped and the brake pressure is reduced to a very low level, the idle torque from the transmission will begin to move the vehicle forward. By maintaining the pressure in a very tight band (typically near 3 bar) such that the vehicle rolling speed is in the range of 0.1 to 0.5 rpm, then slip-stick events between the friction material and disk create the groan.SAE J2786 pdf free download.