Brake lights — we see thousands of them every day, on city streets, country roads and busy highways. When we spot those bright red indicators on other vehicles, the message is obvious: Someone is slowing, perhaps preparing to stop.
Brakes are a vital component of any vehicle, but are perhaps even more important for Class 8 tractor-trailers, which can weigh up to 80,000 pounds. These rigs can’t “stop on a dime,” as they say, so the driver’s reaction time and the condition of the brakes are often the only difference between a normal day on the road and a catastrophe.
Despite being one of the most important systems on a truck, the mechanics of how brakes work are a mystery to most drivers. The expectation is that when the driver steps on the brake pedal, the vehicle will slow and stop. Unfortunately, many drivers aren’t aware there’s a problem with their brakes until they don’t work as expected when driving. By then, it may be too late to avoid an accident.
The luckier drivers tend to find out during a Commercial Vehicle Safety Alliance (CVSA) inspection. While being penalized or placed out of service isn’t a pleasant experience, this scenario is more appealing than an accident.
One part of the problem is that it’s not easy to inspect a truck’s brakes. Most of the components are difficult to get to. Crawling under the truck is necessary, and no one wants to come in contact with pavement in most truck parking areas. In addition, a flashlight is often needed for an inspection, and access plugs or panels may need to be removed to get a look.
Another issue is a lack of knowledge. If you ask the average driver what the acceptable push rod travel is for the brakes installed on the truck he or she is driving, you’ll rarely get an answer. Ask how thick brake pads or shoes are (or should be), and most won’t know that either. Many drivers assume that brake maintenance, like engine or transmission work, is the job of maintenance technicians.
The end result is that brake issues are almost always the top issue in roadside inspections. Even then, unless the driver owns the truck, it’s easier to put the blame for any problems on the carrier. Even so, the driver still pays. Two or more brakes out of adjustment is an out-of-service condition, meaning the driver can’t move until the issue is corrected. For many drivers, that means no miles — and no pay. This gets expensive when delivery appointments have to be rescheduled, sometimes costing the driver a day or more of earnings.
Depending on the carrier, drivers may be responsible for paying all or part of any fines that are incurred during inspections.
Then there’s the impact that carrier and driver share — points on the Compliance, Safety and Accountability (CSA) score and Pre-Employment Screening Program (PSP) record. When, for example, slack adjusters aren’t within required specifications, not just one, but two violations are typically noted on the inspection. The first is a brake out of adjustment; the second is an automatic slack adjuster that failed to maintain the proper adjustment.
In the case of a driver, PSP scores are interpreted differently among carriers. In general, a large number of vehicle maintenance violations on the driver’s PSP could be an indication the driver doesn’t adequately perform pre-trip inspections on their equipment. The PSP can mean the difference between getting a new job and not.
And, of course, any accidents resulting from inadequately maintained brakes can result in serious injury or death, as well as expensive litigation.
At a minimum, a pre-trip inspection should include a check of visible brake parts. Hoses and fittings should be secured so they don’t rub against one another or against vehicle frames or parts, and they should be checked for chafing. There should be no audible leaks. Mounting hardware for air chambers and other components should be intact and snug.
In the case of disc brakes, Bendix recommends checking brake pads for abnormal wear and cracks, and for minimum pad thickness of .125 inch (that’s an eighth of an inch). Rotors should be inspected for cracks and for thickness. Some light surface cracks are acceptable, but they definitely should be brought to the attention of a technician. With the brakes off, there should be adequate running clearance between pad and rotor.
For drum brakes, again, some light surface cracks in the drum are acceptable, but they should be checked. There should be an acceptable amount of free play in the slack adjuster and push rods; the amount differs among manufacturers, so it’s necessary to find out what equipment is installed on the truck. Brakes may differ between axles too, so allowable free play on one may not be the same for another. Shoes should be checked for cracks and breakage, and for even wear. Slack adjusters and S-cams need occasional lubrication.
Braking systems include a compressor, tractor and trailer protection valves, compressed air tanks and various warning gauges, lights and audible signals. It’s important to periodically perform in-cab checks. These involve holding the brake pedal down and watching the gauge for air pressure loss, pumping down the brakes to observe the pressure remaining when warning lights and buzzers activate, and at what pressure the tractor and trailer valves activate. It’s also important to make note of how long it takes for the compressor to build air pressure back up.
Automatic slack adjusters have been required by regulation since 1994 for tractors and since 1995 for trailers. Unless your equipment is very old, chances are slim that you’ll encounter manual adjusters. If you do, it’s important to know how to keep them in adjustment to maximize your braking power. Manufacturers of automatic slack adjusters recommend that they NOT be adjusted between brake jobs. If the brakes are out of adjustment, it’s an indication the adjuster is no longer working correctly and must be replaced. The adjustment screw on the automatic adjuster is used only for resetting the adjustment after a brake job.
When it comes to brakes, it doesn’t much matter whether the driver or a technician inspects the brakes; what matters is that it gets done periodically. With preventive maintenance intervals of 60,000 miles or more, brake systems may not get the attention they need to catch potential issues before they become safety problems.
Any time a tire is removed, of course, a thorough inspection of the brakes on that axle end is a must. If the driver isn’t qualified to fully check brake components, the vehicle should be scheduled for a check by a technician at a company or road vendor location.
Brakes are easy to take for granted. Issues like improper adjustment or inadequate shoe thickness may not show up under “normal” braking conditions, but when a panic stop is necessary under a full load, those issues can suddenly become critical.
Make sure you have the ability to stop when you need to by being sure your brakes are in tip-top shape.
Cliff Abbott is an experienced commercial vehicle driver and owner-operator who still holds a CDL in his home state of Alabama. In nearly 40 years in trucking, he’s been an instructor and trainer and has managed safety and recruiting operations for several carriers. Having never lost his love of the road, Cliff has written a book and hundreds of songs and has been writing for The Trucker for more than a decade.