Why are we getting brake adjustment violations?
Brake Adjustment Violations! Why?
With automatic slack adjusters required by regulation on trucks and tractors since 1994 and trailers since 1995 why do we have brake adjustment violations? The first reason is that this is a mechanical device which if it is not maintained properly can malfunction and contribute to brakes out of adjustment. Slack adjusters on all commercial vehicles should be inspected and greased every 90 days.
Another reason is that a portion of these violations can be attributed to the technical working of the automatic slack adjuster. Professional drivers will maintain a space cushion between themselves and the vehicles in front of them. Then when applying the brakes, they will usually apply the brakes with 15% to 25% air application. A driver will only apply the brakes with greater than 60% air application in a defensive action. These braking incidents are called “Panic Stops” or “Rapid De-acceleration Occurrences.” The analysis reflects that most professional drivers will require less than six of these brake applications per 1,000 miles driven. Most of our Navistar trucks are equipped with a “Stroke Sensitive” automatic adjuster. This type of slack adjuster adjusts the brakes on the return stroke. This adjustment occurs only when the application is greater than 60%. The better the driver, the less opportunity there is for automatic brake adjustment. To ensure that the brakes are always in adjustment, we recommend the following:
- During your pre-trip inspection, complete 10 full brake applications while the unit is parked. A slack adjuster will adjust approximately ½ inch with every 10 full brake applications. Including this procedure as part of your pre-trip inspection will ensure that your brakes are always an adjustment. In the event of a roadside inspection, repeat this process before the inspection process. This will ensure that the automatic slack adjuster has adjusted the brakes to compliance.
- During the Pre-Trip inspection, a driver is required by the Federal Motor Carrier Safety Administration to check the low air pressure warning device.
This should be audible at 60 psi. The air pressure must be lowered to 60 psi to check this device. If, while accomplishing this portion of the inspection, a driver would fully apply and release, the air pressure should drop approximately four psi with each application.
Squeaking Brakes – Another condition attributed to “feathering or low psi” brake applications is noisy brakes when stopping. This is often created by crystallized lining, which occurs when the brakes are repeatedly applied with low psi. This can be minimized with four or five firm brake applications or rapid deacceleration stops. If your brakes are noisy, try bringing the vehicle to a stop with four or five firm brake applications weekly. Always check to see no vehicles following you when you perform this
procedure. Drivers who does not feel their brakes are operating normally must communicate this to their service provider on their daily vehicle inspection report. Drivers should NOT try and manually adjust automatic slack adjusters! A trained technician should only perform this.