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SAE J2521 noise tests are conducted to examine the impact of shim and grease on brake squeal generation. The impact of adhesive (bonded) shim, clip-on shim and grease for noise generation are examined. Low frequency squeal is eliminated by the application of grease on both adhesive (bonded) shims and clip-on shims. The role of shim and grease for reducing brake squeal is discussed. Adhesive (bonded) shims were found to be effective for high frequency squeal (pad bending mode) by increasing damping. Grease is effective for low frequency squeal (pad rigid mode). The mechanism to eliminate low frequency squeal by the application of grease is investigated. Friction between the shim and caliper piston/finger is reduced. Pads contact directly to the anchor bracket. As a result the contact stiffness is increased. The mechanism is confirmed by experiments.

In the past, in order to have good brake effectiveness, it was necessary to adopt high coefficient friction materials for pads or linings, or enlarged brake effective radii. But high coefficient material can create problems such as noise or vibration. And increasing effective radii is limited by the wheel package. A high pedal ratio can provide good effectiveness, but also leads to long pedal travel and poor brake feel. Specifically for trucks and SUV's with large GVW's, it can be difficult to achieve both good brake effectiveness and good pedal feel. In response to this difficult design challenge, a double link-type variable ratio pedal was developed for a production application.

For low frequency brake squeal (1-3kHz) anti-squeal shims are not always effective Development of an appropriate reduction method is therefore an important issue Theoretical analysis of low-frequency squeal has been shown by many papers But presently the squeal reduction method is not sufficient for vehicles In this study we measured brake component frequency response during brake application with stabilized friction surface condition This method enabled us to find the optimal rotor natural frequency and reduce low-frequency brake squeal

At an early stage of developments, brake performances are usually obtained from a simulation using a brake dynamometer. However the brake parts on the dynamometer will not operate at exactly the same temperature as that fitted to a road vehicle, because the cooling factors are different. Also the load on the brakes on the dynamometer is different from the actual load. The effects of temperature and load on brake performances were investigated and it was found that over a considerably wide range the frictional coefficients of brake materials are only minimally affected by the cooling factors and load. Brake performances calculated from the experimental data obtained from dynamometer tests using different line pressures and velocities as parameters show good coincidence with the actual road test results, so the simulations can be used to effectively estimate brake performance at planning stage of the vehicle.