Proper Air Brake Inspections Are Critical To Safe Operation

Did you know that almost 1,600 commercial motor vehicles were put out of service during Brake Safety Day this past April? Out of the over 11,000 inspections completed in North America, over 13 percent of inspected vehicles got an out-of-service violation because of substandard brake maintenance. It is critical that trucking companies pay close attention to the condition of their air brakes, and not just because they are worried about a violation. Brakes play a critical role in the overall safe operation of commercial motor vehicles.

Chamber Size

That’s why we wanted to devote this week’s blog post to ensuring your air brakes are in proper order. Are you aware of all the steps required to ensure the functionality of your braking system?

First, make sure that brake adjustments and checks are completed before the brakes are in use. When the brakes are heated up, stroke measurements can be far longer. Why? Because the brake drum itself expands when in use. Cold brake check measurements are key to getting a proper reading.

The brake chamber size must be determined while in this state. First, technicians will want to locate the size markings on both the clamp and chamber body. Are those markings easily readable? If not, special calipers can help technicians ascertain the proper chamber measurement size.

Ranges for brake chambers generally fall between 6 and 36. Steer axle brakes will be smaller due to the nature of the steer axle. Expect those measurements to fall somewhere between 12 and 20. Heavier axles, by their nature, rely on larger chamber sizes.

Pushrod Stroke

What method will you use to determine a brake’s applied pushrod stroke? There are a couple to choose from. First, you can mark the pushrod with a reference point. This will allow you to operate the brake then go back and see where the measure met up with actual performance.

Second, you can measure the released position of the pushrod. Make sure to take account of the distance from a single point on the pushrod body to a fixed point near the brake chamber. If that measurement is off at all, you may of a problem.

Wherever your measurement comes out at, you will want to lower the vehicle’s air pressure through either running the engine or pumping the brake pedal. It will be important to ensure you have reached between 90 and 100 psi on both the primary and secondary tanks. With the correct air pressure indicated, make sure you apply and hold pressure to the brake pedal to get a true reading.

Fortunately, many brake OEMs already make their products with marked pushrods. This allows technicians to quickly determine whether a brake is out of adjustment or not without having to go through the manual checkmark process. Brakes that are within alignment will show the marking as being inside the body of the brake chamber. Conversely, if any part of the indicator is visible, the brakes either need to be flushed or are out of alignment.

Checking Adjustments

To get a good idea of whether brakes are adjusted properly or not without a fully-fledged inspection is another option. Ensure the vehicle is properly secured, then grab a prybar and pull back the push bar from the brake chamber. What is the push bar’s range of motion? If you are nearly an inch within stroke-free distance, your brake may be out of adjustment.

Without brakes, there is no safe operation of any vehicle, commercial or otherwise. Always ensure your technicians are up-to-date on how to check a rig’s air brakes and you can rest assured that your fleet is operating safely, day-in and day-out!