How to heal brake squeal

June 27, 2003

From Porsche 911s to ageing Minis, no car is immune to the irritation of squeaky brakes, but now US engineers may have come up with a low-cost solution, writes Natasha Gilbert.

Engineers at the Georgia Institute of Technology have developed an electrical squeak suppression system that could be factory-fitted to new cars and retro-fitted to older models for as little as £18.

The most annoying, slow-speed squealing can occur when brake pads vibrate against the brake discs, generating a high-pitched sound. This problem does not affect brake operation but it can lead to the needless replacement of brake pads.

Ken Cunefare, a professor at Georgia Tech's School of Mechanical Engineering, and Jeff Badertscher, research assistant, have designed a cylindrical actuator made from a material that stretches or contracts when an electrical current passes through it.

The actuator vibrates at a high frequency that suppresses the lower frequency vibrations of the squeaky pads. The system is connected to vehicle brake lights and comes on when the brakes are applied.

The researchers claim their system works despite temperature and humidity changes and normal brake wear, all of which can change the squeak frequency.

Professor Cunefare said the system is simpler and cheaper than other engineers' attempts to stop brake squeal.

"Our system does not need to detect the presence of squeal. All it needs to know is that the brakes have been applied," he said.

He is confident of the system's long-term reliability and that it has minimal or no impact on brake performance.

"This is fundamentally a fail-safe system. If an actuator were to break, there would still be another load path to allow the piston to operate the brakes," he said.

The findings are published in the Journal of Sound and Vibration.

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