Prepare Now for Brake Safety Week - September 11-17

Brake Safety 2thumb4

During the week of Sept. 11-17, 2016, law enforcement agencies across North America will conduct inspections on large trucks and buses to identify out-of-adjustment brakes, and brake-system and anti-lock braking system (ABS) violations as part of the Commercial Vehicle Safety Alliance’s (CVSA) Brake Safety Week, an annual outreach and enforcement campaign designed to improve commercial motor vehicle (CMV) brake safety throughout North America.

Brake Safety Week is part of the Operation Airbrake program sponsored by CVSA in partnership with the U.S. Department of Transportation’s Federal Motor Carrier Safety Administration (FMCSA).

Air Brake Adjustment

In North America there are far too many vehicles put out of service in roadside inspections for brakes being out of adjustment.  With today’s technology, proper maintenance and driver training, I believe it is possible to practically eliminate brakes being out of adjustment.
Can you or your drivers answer the following questions correctly?

  1. Do automatic slack adjusters on ‘S” cam brakes require checking?
  2. When checking free play on a type 30 brake chamber, what distance is preferred?
  3. Can you explain the difference between free play and power stroke?
  4. What is the adjustment limit for a standard type 30 brake chamber? Long Stroke type 30 ?
  5. Can you explain how to adjust automatic slack adjusters from the cab?


  1. Yes
  2. Approximately 3/4 of an inch
  3. Free play is the distance you can pull the slack adjuster by hand Power stroke is an application of the foot peddle or hand brake
  4. Standard type 30 is 2 inches. Long Stroke type 30 is 2.5 inches
  5. The following process applies for both the tractor and trailer and they may be done separately.

With engine running and brakes released, make up to 10 full brake applications without the air pressure going below 100 psi, in other words you will make 3 full brake applications, then stop, let the pressure build back up to maximum pressure make 3 more full applications etc, You will do this using the foot pedal for the tractor and the hand valve (spike) for the trailer, It is preferred you do each unit separately.

Once this has been done and all brakes are adjusted correctly, make 1 or 2 full brake applications every day when the brakes are cold. For example, start your truck up in the morning, build air pressure to maximum, release park brake, make 1 or 2 full brake applications with the foot pedal, for the trailer make 1 or 2 full brake applications with hand valve (spike).
Please Note: Even for drivers that do the above process every day, regulations still require drivers to physically check brake adjustment daily, to do this you have to get under the vehicle and physically check the free play at each chamber, remember for both type 30 chambers, standard or long stroke, you are looking for approximately ¾’s of an inch free play, any more than that, go though the above procedure, re-check the free play. If you should have a chamber that is still not adjusted correctly, it has to go to the shop.