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Brake Squeal - A Practical Approach

Brake Squeal - A Practical Approach. D.Williams. BMW Group Foundation Brakes Brake Refinement. Introduction. Brief Outline Of Brake Squeal Problems Faced By Industry. Description Of Techniques Applied To Identify Squeal Problems. Rectification Techniques Available.

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Brake Squeal - A Practical Approach

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  1. Brake Squeal - A Practical Approach D.Williams BMW Group Foundation Brakes Brake Refinement

  2. Introduction Brief Outline Of Brake Squeal Problems Faced By Industry. Description Of Techniques Applied To Identify Squeal Problems. Rectification Techniques Available. Techniques Under Development. Future Direction.

  3. Brake Squeal Brake Squeal Is Consistently Responsible For A Significant Warranty Bill . A Large Percentage Of All Vehicles Have Warranty Work In First 12 Months For Brake Squeal. Clearly Not In Accordance With Ever Increasing Customer Expectation.

  4. Current Technique • 1) Rig Test At Friction Suppliers. • Pad selection includes Squeal performance. • Work carried out without any noise fixes. • 2) Rig Test at Caliper Supplier. • Tests conducted on specific noise dynamometer which MUST include a complete suspension corner. • L22 Experience!

  5. Current Technique • 3) Squeal Rectification at Supplier. • Two potential approaches: • Below 5kHz Caliper modifications. • Above 5kHz Shim addition to backplate • Comment on L22 Experience • 4) Vehicle Validation • Having achieved a quiet rig result vehicle running is conducted in worst case conditions - Typically Mojacar or LA city.

  6. Brake Refinement • Tools Used For Problem Rectification. • Currently rely on “Black Art” pad modifications or shim additions. • Mass additions to caliper antinode • Goal - Development Rules Leading To Quiet Brake Design .

  7. Brake Refinement Design Guidelines: Frequency Movement To Disc To Make Improvement. Pad Shape - Are Chamfers A Good Thing? Disc guidelines, What Can Be Done.

  8. Technique Development At BMW Non Contacting. Robust. Full System (In Squeal Generating Conditions). Including Time Domain. Comment: Double Pulse Laser Holography - Snap Shot Only!

  9. Hi Speed ESPI Similar Technology to Laser Interferometry. Records deflection at a rate up to 40kHz. Includes Time Domain. Low Power Laser Requires Retro reflective Tape. The Squeal Rig

  10. Animations Actual ESPI Anti Node Rotation. Approximately 3100/4: 775 Hz (Frequency/Mode Order) Modelled ESPI

  11. Summary Development lead. Costly In Time And Resource. Comment : All Suspension Components Must Be To Production Intent Before Refinement Work Can Commence. Disc Models Give Good Correlation - Next Step requires Good Pad Data, i.e. Compressibility, Damping And Friction Coefficient at squeal generating conditions.

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