Heavy-duty: 2023 HDAW event theme is ‘Shift. Adapt. Grow.’
Commercial Vehicle Safety Alliance’s CSA violations should be an unnecessary problem, especially since they can lead to costly delays, and unexpected downtime may cause fleets to lose customers not only because of delays.
After citations related to lighting problems, brakes are the second most commonly penalized item—18.7% of violations handed out by the CVSA in 2014 were brake-related. We asked brake experts about common issues that lead to CSA violations, and how they can be prevented.
“DOT inspections are a fact of life in the trucking industry,” begins Greg Sturdy, director of wheel end product engineering for Accuride, “but with proper attention and preventive maintenance, your brake system needn’t cause concern for inspectors.
“Drivers who use the ‘feel’ or appearance of their vehicle as their primary method of inspection can develop a false sense of security about their brakes,” he continues. “There are several preventive maintenance steps that can address any potential areas of concern and help avoid CSA issues.”
Sturdy states that improperly maintained components can lead to premature or uneven wear and improper clearances. A quick rundown of potential component issues includes:
- Drums and wheels not being mounted or piloted properly;
- Wheels that are improperly torqued;
- An improper setup of automatic slack adjusters [ASA] and the air disc brake system;
- Using impact guns on automatic slack adjusters (ASA) or air disc brake adjusters (ADB) or other components during installation or adjustment; and/or
- Improper service of greased joints for slack adjusters, lining bushings and s-cams.
Sturdy adds that ABS system yellow lights should be investigated as soon as possible, since they indicate problems within the system and can lead to red lights and potential damage to other components later on. Additionally, air leaks should be investigated and fixed as soon as possible before they lead to damage or excessive wear in other components. Sturdy further notes that rust and corrosion on the wheels and wheel-end components could lead to them receiving more scrutiny from inspectors.
“With nearly 200,000 violations recorded by the CSA in 2015, one of the most common issues was brakes that were out of adjustment,” says Jeff Wittlinger, business unit director of wheels and braking systems at Hendrickson.“Inoperative or poorly maintained brakes are also concerns that could lead to a violation which could put a vehicle out of service. Brake violations account for over 25% of all vehicle violations in 2015. Such violations can negatively impact a fleet’s CSA score; the brake-related violations account for four points.”
Dennis Griffin, product manager of commercial vehicle friction for Federal-Mogul Motorparts, lists the following as some of the most common brake shoe-related violations:
- Cracked brake lining—cracks or voids that exceed 1/16 in. in width observable on the edge of the lining;
- Portion of a lining segment is missing such that a fastening device (rivet or bolt) is exposed when viewing the lining from the edge;
- Cracks that exceed 1 1/2 in. in length;
- Loose lining segment;
- Complete lining segment missing;
- The friction surface of the brake drum and the brake friction material are contaminated by oil or grease; and
- Lining thickness less than ¼ in. or to worn into the wear indicator if lining is so marked, measured at shoe center.
“One of the most common and preventable CSA brake violations is improperly adjusted S-Cam brakes,” says Jeff Geist, director of engineering for the brake products group at Stemco. “Since 1994, all commercial vehicles in the U.S. are required to use automatic slack adjusters. These devices work very well, compensating for brake friction and drum wear and maintaining acceptable stroke length, but they do need to be installed correctly, checked often and maintained on a regular schedule.
“Each manufacturer specifies a setup procedure and although similar in principle, the actual specifications may differ,” he continues. “This is important to note especially if a different brand is used for replacement. An improper setup angle may lead to the unit malfunctioning and not maintaining the proper adjustment. Oftentimes a technician may just bolt in an available replacement without realizing that a setup procedure is necessary. The best advice is to check the ASA operation and measure the stroke length frequently.”
ASAs should only require adjustment when initially installed. If the ASA falls out of or does not maintain adjustment this can be a signal of other foundation or parking brake problems, such as worn S-Cam bushings, worn anchor pins, worn clevis or pins, improperly functioning air chamber, distorted or broken mounting brackets, etc. Therefore prior to replacing a suspect ASA, these components should also be checked, or the problem is very likely to recur.”
“Among the most common preventable issues is brake adjustment,” according to Jon Morrison, president of WABCO Americas. “In the Commercial Vehicle Safety Alliance’s annual International Roadcheck, brake adjustments were cited for violations in 18% of the vehicles that were placed out of service. Air disc brakes provide an effective solution because brake adjustment is done internally, thereby eliminating out-of-adjustment concerns.”
Air disc brakes
In recent years, ADBs have been slowly, but steadily gaining ground in the marketplace. ADBs offer improved stopping distances, reduced maintenance and longer life, but cost more and weigh more than the traditional drum brakes; consequently, they continue to lag far behind drum brakes in terms of adoption. So what unique problems do air disc brakes present?
“Currently, the air disc brake vs. standard drum brake designs are visually different even to the untrained eye,” says Bill Hicks, SAF-Holland’s director of product planning for the Americas. “The biggest difference is that the adjustment mechanism of the ADB is enclosed, thus making any measurement such as the current open drum brake slack adjustment more difficult. The upside is that these systems are protected from environmental and road debris impacts and have proven to be very reliable. Thus, the inspection methodology for each design is different and has been addressed via industry standards such as TMC recommended practices.”
“The CSA has fewer inspection guidelines for air disc brakes, as does the TMC,” Accuride’s Sturdy says. “Technicians and inspectors need to familiarize themselves with individual ADB systems. Looking for missing or damaged components is the most common inspection step. Inspectors also check joints for tightness. So it’s important to maintain the proper tolerances. There are not legal stroke checks for ADBs, which can help avoid out-of-service issues.”
Sturdy notes that servicing is easier for drum brakes than for ADBs, since the disc brakes require the removal of the hub for servicing; hub replacements can cause damage to seals, bearings and endplay, so care must be taken when performing hub maintenance and replacement.
“Although they do not have grease points, disc brakes should be inspected and maintained at regular intervals, similar to drum brakes,” Hendrickson’s Wittlinger says. “Pads and rotors wear just as brake linings and drums do.
“It is not recommended to replace only one brake pad or the pads on only one side of the axle,” Federal-Mogul’s Griffin says. “Brakes should always be replaced on both sides of the axle. Thorough inspection of the pads and the rotors can prevent out-of-service brake violations.
“For air disc brake systems, it’s important to note that ADBs are handed for driver rotation, and that calipers and carriers are not interchangeable,” Accuride’s Sturdy adds. “Tappet holes in ADB pistons must be kept clear to allow air to vent. Also, check caliper slide for movement on both brake pads (IB/OB) and the caliper itself. Adjusting the ADB or slack while driving forward should be done lightly for brake pad/lining contact, not force. Over-driving can lead to broken ADB shear pins.”
We also asked our pool of experts whether there are certain CSA issues that disc brakes will help fleets avoid.
Hendrickson’s Wittlinger points out that there is a distinctive difference between drum and disc: The adjustment mechanism for a disc brake is contained within the caliper housing, so it cannot be easily inspected on current disc brake designs, which limits the possibility of an out-of-adjustment violation.
This, SAF-Holland’s Hicks notes, is significant—the majority of brake issues found in CSA inspections are out-of-adjustment violations.
In addition to ADB adjustment being done internally, other advantages include reducing stopping distance by nearly 10% to 15% compared with today’s average drum brakes, almost completely eliminating brake fade or pulling, extending service intervals up to two times versus drum brakes, and the ability to exchange four brake pads in the time of one drum lining, according to WABCO’s Morrison.
“It’s important to think preventively,” Accuride’s Sturdy says. “Routine and scheduled maintenance should be performed at regular intervals to ensure optimal system performance. Follow the OEM and manufacturer’s recommended intervals.”
“Air dryer systems also should be checked regularly to ensure that no moisture is in the system, since the air system can cause downstream issues in brake systems,” he adds. “If components are worn, don’t take chances. Replace them as needed to ensure safe, trouble-free operation. Look to replace wheel-end components at each wheel as families, at a minimum. When conditions call for replacement, Gunite recommends replacing brake components across the entire axle. Routine system maintenance should include checking the following:
- Joints and grease with manufacturer recommended lubricants.
- Clevises and pins for seizing, clean, grease, and replace them when necessary.
- Brake shoe rollers and s-cams for wear, mushrooming or flat spots.
- Brake linings for wear (or mark), cracks, gouges, glazing, taper. Unequal wear from lining to lining, from brake block to brake block, or pad to pad.
- Brake linings/pads for cracks, mushrooming, or gouges.
- Brake drums for diameter, taper, heat checks, gouges, glazing, hot spots and roundness.
- Rotors for all the same conditions, exchanging thickness variation for roundness.
- Brake shoe springs for weakness or missing components.
- Wheel bearing end play, per the manufacturer’s recommended specifications.”
During preventative maintenance, brake pads should be checked to see if they need to be replaced, according to WABCO’s Morrison. This includes:
- Checking brake pad thickness. Burned, glazed or oil-contaminated brake pads must immediately be replaced.
- Brake pads should always be replaced by axle using a new retaining system for pads and pressure plates.
- To avoid damaging the brake disc, brake pads should be replaced no later than at the point when they reach the wear limit at their weakest spot. Residual pad thickness must not be less than 2 mm above the backing.
During inspection with the wheel removed:
- Check boots, seals and end-caps for damage or cracks;
- Measure pad wear;
- Inspect the rotors for cracks;
- Check running clearances and adjuster operation;
- Check caliper slide movement (should move easily by hand);
- Check caliper guiding clearances; and
- Inspect hoses and brake exterior for damage.
WABCO’s Morrison recommends using OEM-approved replacement parts due to their higher quality.
“Conducting routine preventative maintenance practices will identify most potential problems,” says Daniel Philpott, manager of engineering, brakes for Meritor. “Many common CSA violations can be avoided by performing a pre-trip inspection—especially lining thickness, confirming that brakes are not out of adjustment, and checking to see if any damage exists. In order to prevent these issues fleets need to make sure to change wearable parts within wear limits.”
“Drivers should conduct daily pre-trip checks and system leak tests,” advises Richard Nagel, director of marketing and customer solutions, air charging for Bendix Commercial Vehicle Systems LLC. “To check for leaks, Bendix recommends a 90 to 100 PSI brake application, followed by a walk-around vehicle inspection that includes listening for audible leaks.
“During visual inspections, check the air system carefully for loose hoses, and at the wheel ends, make sure that the air chambers, pushrods and slack adjusters are not damaged or hanging loose,” he adds.
“For air disc brakes, check the guide pin boots and tappet boots to make sure they are intact, without cracks or tears that could allow moisture inside,” recommends Keith
McComsey, director of marketing and customer solutions for Bendix Spicer Foundation Brake LLC. “Although it’s not necessary to get under the vehicle every trip, Bendix recommends that once or twice a week, drivers check air disc brake rotors for cracks, and inspect the lining wear on drum brakes without dust shields, since this can be done without removing the wheel.”
Dave Engelbert, chief engineer at Haldex, recommends using glad hand screens and inline air filters on trailers to prevent contaminants from fouling up ABS and air brake valves causing premature failure from leakage or seizing. Screens and filters prevent contaminants from entering the air brake system, but eventually must be serviced and replaced. The inspection of the trailer’s glad hand screens and inline filters must be part of the trailer brake system’s preventive maintenance program.
Engelbert also recommends that the vehicle’s air reservoirs be drained at the end of the vehicle’s service day. Water accumulates in the air brake reservoirs, and water held for extended time periods can lead to corrosion. Corroded pieces from inside the reservoir can eventually break away into the air brake system, fouling up air brake valves and causing the valves to leak. In winter months the use of alcohol in the vehicle’s air brake system should be minimized or not used at all, he advises. Alcohol can swell the rubber components inside the air brake valves causing premature failure because of leakage or seizing.
Stemco’s Geist also notes that air disc brakes use an internal mechanism in the caliper to compensate for friction and disc wear; this being the case, conventional stroke length cannot be measured in the field. This places more responsibility on the driver to observe and report unusual braking performance or operation.
“Replace brake shoes that have defective lining conditions,” recommends Federal-Mogul’s Griffin. “If one brake shoe is defective, it is important to replace all brake shoes on the axle. Replacing one brake shoe or just replacing the shoes on one side of the axle is not recommended.”
Griffin also recommends replacing oil- or grease-contaminated brake shoes—not trying to clean them. If just one shoe is contaminated, he says, all of the brake shoes on the axle should be replaced.
“Train drivers on what to look for during their daily ‘walk around’ inspections,” Hendrickson’s Wittlinger advises. “For instance, look for signs of oil around the hub and wheel and ensure hoses are not touching wheels or brake equipment.”