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The National Safety Code madates that every driver of a commercial vehicle equipped with air brakes must check push rod travel every day.

In many jurisdications, drivers are allowed to use the pry bar method; in others , they must use the applied stroke method.

Know how you are to determine if the brakes are in adjustment for your province or territory.

The Pry Bar Method can also be called the Free Play Method.


 TOOLS REQUIRED: gloves, safety glasses, wheel chocks, pry bar, device to mark push rod at fix point.

 1) Block wheels, release spring brakes and ensure system pressure is above 100psi.

2) Mark the push rod at a fix point.

3) Using a pry bar, extend the push rod out of the brake chamber as far as it will travel.

4) The push rod should not extend more than 1/2" & 3/4 " inch from the brake chamber. (Approximately the width of your thumb nail.)

There is a small clearance between the brake shoe and the drum. When a brake is in adjustment, that distance is approximately 3 sheets of paper. And the push-road travel taht can be pried out of the brake chamber will be between 1/2" & 3/4 " inch. If the push rod travels to 3/4 " inch, the brake either needs to adjusted or perhaps repaired.

5) If the push rod travels more that 3/4" inch, the manual slack adjuster has to be adjusted.

6) If the vehicle is equipped with an automatic slack adjuster, it may have to be assessed & repaired by a qualified mechanic.