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E-Board S-Cam Brake Bias (EB-SC) Foundation Brake Diagnostics

Foundation Brake Diagnostics

What is S-Cam Brake Bias?

Brake bias is a relatively common s-cam brake issue. Although it is more commonly associated with trailer brakes, it also occurs on truck, bus and tractor drive and steer axles. Brake Bias is caused by the misalignment of the stationary wheel brake components and the actual center of rotation of the brake drum and wheel. The resulting off-center position of the internal brake components results in the uneven contact of the brake shoes against the brake drum.

Brake Bias Can Result In:

  • Brake Noise and Vibration
  • Seriously Reduced Service & Spring Brake Performance
  • Automatic Brake Adjuster Over-adjustment
  • Uneven Brake Lining Wear
  • Brake Lining Overheating
  • Brake Lining Deterioration (break-down)
  • Brake Fires 

Brake bias often goes undiagnosed, either as a result of the servicing technician not being aware of the potential problems that brake bias can create or simply not knowing how to identify and correct the condition.  In either case, the results can include any or all of the issues listed above.

About E-Board S-Cam Brake Bias Edition

AIR BRAKE Interactive E-Board S-Cam Brake Bias Edition is the most comprehensive teaching resource ever developed on the subject of S-Cam Brake Bias. Designed and developed specifically for technical school and fleet air brake service instructors, the program consists of a comprehensive Instructor’s Reference and Presentation Guide supported by a state-of-the-art multimedia presentation. This program will provide your students or service technicians with the knowledge and skills necessary to identify and correct s-cam brake bias.

E-Board S-Cam Brake Bias Content

Introduction – A Brake Bias Scenario: Presents a typical brake service scenario where brake bias is overlooked and identifies the potential effects on brake performance, durability and vehicle safety.

Precision S-Cam Brake: Illustrates in a detailed animation the components and assembly of a perfect s-cam brake.

Typical S-Cam Brake: Identifies the manufacturing materials and processes used to produce axles and s-cam brake components, and how inaccuracies in the manufacturing process can combine to create brake bias.

What is Brake Bias? Identifies in detail what brake bias is, where it occurs and how it can influence brake performance, service life and safety.

What Can Cause Brake Bias? Identifies the variables in each axle and the s-cam brake components that can contribute to brake bias.

Brake Linings: Identifies and discusses brake lining crowning, coining and initial growth.

Normal Brake Application: Illustrates in animation the function of a non-biased s-cam brake and points out the factors associated with proper brake performance.

Brake Bias Scenarios: Illustrates in animation cam bias, anchor bias, primary shoe bias, secondary shoe bias and combination bias and identifies the subsequent issues related to s-cam brake performance and service life.

Identifying Brake Bias: Illustrates brake lining wear patterns that indicate brake bias, and details the procedure for measuring brake bias as part of a brake shoe and drum replacement procedure.

Other Potential Factors: Identifies a common but dangerous procedure often used in attempting to overcome brake noise and/or other brake performance issues. Discusses and illustrates the importance of proper brake drum mounting and discusses how brake bias can cause some automatic brake adjusters to over-adjust.

For more information and/or to discuss with one of our expert teaching resource developers, please contact:

Bryan Duross
Telephone: 519-621-0708
E-Mail: bduross@sentex.net