Auto-Adjusting Leading/Trailing Shoe Car Drum Brakes

Motor manufacturers are still using leading/trailing drum brakes on the rear axle of passenger cars. The main reasons for this persistence are that handbrakes can be incorporated which give similar performance in either direction, and have simple but very effective automatic adjusters.

This paper describes two brakes, both intended to use with forward pull handbrakes, each having a very different automatic adjuster. One being a ‘one shot’ type and the other a linear incremental type.

The construction, function and advantages of each are outlined together with the main parameters which affect the degree of adjustment which can take place.