Although the government keeps delaying the implementation of new stopping distance regulations, suppliers have been active in developing products that will help fleets minimize costs related to compliance when the regulations are finally enacted. More than two years ago, the National Highway Transportation Safety Administration (NHTSA) first published a Notice of Proposed Rulemaking calling for a 20 to 30 percent reduction in stopping distance requirements for combination vehicles.
Although NHTSA has not yet released a final rule, there was an indication that it was going to do so last spring. That never happened because the agency was reportedly fully involved with what it considered to be higher-priority rulemaking activities.
More recently, NHTSA unofficially promised release of the final rule by the end of this year, but that may well be delayed again, most likely, until early next year – possibly February. Actual implementation could be two years after the announcement is actually made. If that were to happen, these mandated major brake changes would coincide with the release of the 2010 exhaust emissions changes. This was certainly not the industry-wide desire during the original proposed rulemaking process back in December 2005. At that time, suppliers, as well as fleets, were hoping for implementation in 2008. That would put it far more comfortably in between the 2007 and 2010 emissions requirements.
NHTSA understands the industry’s concern about the two mandated changes being required simultaneously and may move implementation forward to 2009, but that won’t be known until the final announcement. Randy Petresh, vice president for technical services at Haldex Corp., says, “I believe they’ll shorten the customary time between the announcement and implementation, and I think they’ll have a good chance of doing so because we’re not inventing any new hardware or equipment.”
While the proposed stopping regulations will only apply to heavy trucks, it is interesting to note that NHTSA continues its R&D activities related to air and hydraulic braked straight truck and bus vehicles at the Transportation Research Center in Ohio. A series of test reports are expected to be published by NHTSA in the next four to nine months covering these tests and conclusions regarding baseline and potential reduction in stopping-distance performance. This program is being done in cooperation with industry leaders. Paul Johnston, senior director, North American Foundation Brake Business, says, “Meritor WABCO and ArvinMeritor are actively supporting these tests by providing technical expertise and drum and disc brake hardware to NHTSA for these tests.” At this time, NHTSA has not indicated that it has any rulemaking plans for these types of vehicles.
That’s not to say that other plans for heavy trucks won’t be considered in the future. Several years ago, Duane Perrin, then chief of NHTSA’s Crash Avoidance Division for the Office of Vehicle Safety Research, reported ongoing research on stopping distances of heavy trucks at speeds of 75 MPH at an SAE Truck and Bus meeting. These studies were being conducted because most states had legal speed limits for heavy trucks over 60 MPH the speed used for most stopping tests, on portions of their highways. He also pointed out that nine states, even then, had top speed limits of 75 MPH. There is no indication that such studies will result in new regulations, but Perrin did say that NHTSA has plans to gather more high-speed stopping data.
Disc brakes fill the need
Brake suppliers long anticipated new stopping distance regulations, so they proceeded with product development programs that result in designs that comply with the forthcoming requirements.
For the most part, these new designs have already been engineered into today’s trucks, so fleets have the opportunity to spec either drum or disc brakes with the confidence that new vehicles will comply with future stopping standards.
ArvinMeritor’s Johnston says, “ArvinMeritor and its North American partner WABCO have continued to evolve air disc brakes for the North American market regardless of the new regulations.” Last year, ArvinMeritor and WABCO moved all of its air disc activities and products into the joint venture to maximize the synergies of both companies. According to Johnston, the company has been the only air disc brake supplier that introduced product in the1980s and stayed committed to product technology by continuing development and production. Johnston says, “Since the 1980s, the company has produced more than 400,000 air disc brakes in the North American market.”
Johnston tells us that there has been ongoing product development, with the goal of improving both disc brake performance and durability. Among the improvements are synchronized actuation mechanisms that ensure even pad-to-rotor contact and overall wear distribution and electronic wear sensors that can be integrated into a vehicle communication network as well as future electronically controlled braking systems.
Bendix Commercial Vehicle Systems has also developed and is marketing air disc brakes for heavy trucks. Ron Plantan, principle engineer for the company’s Wheel End Group in Elyria, Ohio, says, “We’ve been working on these products since 2000, taking advantage of the European technology of our parent, Knorr-Bremse, and adapting it to the American market. By the way, we will be making 2.8 million air disc brakes in Europe this year. We work very hard on not only improving stopping distances but also making these brakes pleasing to the driver as well as eliminating any compatibility issues. Although we have retrofit disc brakes for test purposes, retrofit is pretty cumbersome. OE is the way to go.”
Bendix uses dual, internally adjusted pistons in its disc brakes, which, according to the manufacturer, allow them to provide precise brake adjustment, better force distribution and more even pad wear than any single piston caliper design. In addition, the Bendix ADB22X brake is the lightest dual piston design available.
Haldex Commercial Vehicle Systems also supplies air disc brakes to the North American heavy truck market. Haldex’s Petresh says, “We are one of the three disc brake manufacturers. Depending on how the OEMs choose to meet the new regulations, we anticipate an increase in the use of disc brakes. That, of course, is an area that would greatly impact Haldex. We expect to see some standard use of disc brakes on steer axles.”
Haldex tells us that vehicle manufacturers in both North America and Europe are currently conducting comprehensive tests on its new fixed caliper dual disc brake.
Haldex and SKF, both headquartered in Sweden, reached a decision several years ago to jointly develop a complete hub and brake unit for commercial vehicles, trucks, buses and trailers. The system is based on the Haldex fixed caliper dual disc brake and SKF’s hub technology. The team’s goal is to develop a compact product with improvements in both safety and performance. The project partners plan to start series deliveries in 2008.
The modular design of the Haldex ModulX Fixed Caliper disc brake is based on a fixed caliper and the dual sliding discs. Although it has the same brake torque as conventional disc brakes, it is lighter and smaller, thus requiring nearly half the clamping force. So, the Fixed Caliper allows for smaller brake chambers and less air consumption.
More space between the brake and rim improves heat management by increasing the cooling off effect and decreasing ice and mud problems. The improved heat management results in longer pad and disc life. The service friendly design of the two-piece caliper allows the discs and pads to be changed without removing the caliper. And, by reducing the number of components, Haldex said it has simplified service and shortened maintenance stops. The Fixed Caliper means fewer axle variants since it can be fit to axles configured for conventional sliding caliper disc brakes.
ModulX brakes are fully-interchangeable from left to right, simplifying inventory demands, increasing cost efficiency and making maintenance more manageable, the company says.
Overall, the modular design, combined with the common parts between different ModulX model sizes, requires fewer part numbers, reducing inventory costs and simplifying maintenance. ModulX is available in four models to meet specific needs.
Don’t beat the drum
When NHTSA first published regulations calling for a 30 percent reduction in stopping distance, the industry’s early reaction was that disc brakes would be the only technology that would satisfy the new law. That, however, is definitely not the case.
Domestic brake suppliers have all developed drum designs to satisfy the coming mandates. Bendix’s Plantan says, “We have high-performance drum brakes that will comply with the upcoming regulations.” These wide brake packages have already become standard specs for many fleets, but the company anticipates more development and use of high-performance drum brake systems to meet the needs of fleets after the new regulations are implemented.
Plantan says, “As I see it, there are minor improvements in lining material, and the brakes are bigger – especially the front brakes. The new drum brakes offer better fade resistance during downhill braking than earlier designs. They are actually closing the gap between drum and disc brakes in this regard, but discs are still superior.”
A mix of drum and disc on a combination vehicle, long considered to be potentially problematic, has become a non-problem. Plantan says, “We are quite comfortable saying that you can put disc brakes on a tractor and not worry about compatibility with the trailer.”
Maintenance concerns
While fleet managers have a choice of both sources and designs when they spec braking systems, according to suppliers, there’s one significant source of problems areas. Petresh says, “The biggest problem is lack of maintenance. Suppliers constantly visit fleets to train technicians. We provide training CDs and tapes. Unfortunately, after we leave, the prescribed maintenance just doesn’t happen. Every one wants to minimize downtime and expenses and maximize productivity. That’s understandable but not at the expense of maintenance because that doesn’t solve the problems we have in the field.”
He goes on to say, “When we’re asked to compensate fleets under warranty for things that are clearly the result of a lack of maintenance, it makes it very difficult.”
Automatic slack adjusters eliminate the need for routine brake adjusting, but they are not maintenance free nor do they last forever. Plantan says, “Maintenance is a key factor with drum brakes. Do not adjust automatic slack adjusters on a regular basis. If they are found to need adjustment, there is something wrong with the system that should found and corrected.”
ArvinMeritor’s Johnston points out some common problems with disc brakes saying “Among the most frequent causes of problems are contamination of the caliper slide pins or internal caliper mechanism and damaged boots and seals that can allow water and contamination to enter the caliper, slide pins.” How can such problems be avoided? His answer is “Regular inspection of brake and rotor conditions (per service and inspection recommendations and literature) along with wheel seal inspections.” Again maintenance!
NHTSA’s pending regulations mandating decreased stopping distances are aimed at increasing highway safety, a concern high on the list of all fleets. Even before the laws have been implemented, suppliers have delivered systems that will help operators improve the safety on our roads.
About Retarders
NHTSA recently published an overview of retarder technology.
Retarders, all of which can be turned on or off by the driver, offer another way to slow down, lessen the need to use the brakes and reduce brake wear. As with cruise control, retarders should never be used on wet, icy, or slippery roads. There are basically three types of retarders.
Exhaust brakes use a valve installed on the engine exhaust system to restrict or hold back the engine exhaust. A closed valve causes a buildup of exhaust gases that flows back into the combustion chamber of the cylinders. Pressure buildup in the cylinders creates a power loss by restricting the fuel mixture delivery to the cylinders.
Engine compression brakes (often referred to as “Jake Brakes” from the Jacobs Vehicles Systems Co.) are installed in the engine cylinder head and directly control the engine exhaust valves or throttle valves. If an engine compression brake is installed on a 300-horsepower engine, you can expect up to 150 horsepower from the engine to slow the vehicle. When the retarder is turned on, the engine compression brake activates when you remove your foot from the throttle. Most engine compression brakes have multiple settings.
For example, a Jake Brake has three settings. The use of an engine compression brake is restricted or prohibited in some areas due to federal, state or local noise standards.
A driveline retarder works by generating force, which causes the driveshaft to resist turning, thereby slowing the vehicle. Hydraulic is the most common type of driveline retarder. The efficiency of driveline retarders (horsepower available to slow the vehicle) is generally greater than exhaust brake and engine compression brake. Driveline retarders can continuously provide smooth retardation over a wide range of speeds. Remember that activation only occurs when the retarder master switch is turned on. It is important to remember that a hydraulic driveline retarder is cooled by transmission oil, and excessive use can cause overheating. It is generally possible on newer vehicles to interconnect the retarder and cruise control to keep the truck at a constant speed as it travels up and down hills.
Maintenance Tips
ArvinMeritor offers the following tips for brake system maintenance.
AUTOMATIC SLACK ADJUSTERS
Just because it says it’s automatic doesn’t mean it’s maintenance free.
For automatic slack adjusters (ASAs) to do their job, you must do yours. That means checking to ensure that the slacks were installed properly. Also, make sure the ASAs are lubricated. Check the brake system for damage, since ASAs are not a cure-all for deficiencies in the foundation brake.
CAM BRAKES
Be sure to replace the cam brake return springs at every reline.
Not everyone believes it is necessary to replace cam brake return springs each time cam brakes are relined, but wouldn’t you rather do it then, instead of on the road? The return spring is critical to alignment, the accurate return of the brake away from the drum and brake adjustment with the automatic slack adjuster.
CAM BRAKE LININGS
The brake lining block must be OEM quality.
Vehicle brake systems require the correct lining material to perform a specific job. If the type of lining material is changed, the job isn’t done properly. Insist on the same brand of friction material as the OEM quality to ensure fewer replacements and greater compatibility with your present system.
PLAN AHEAD
Replace all the hardware when servicing cam brakes.
Planning ahead could avoid unnecessary downtime for your vehicle. When you service your cam brakes, take time to replace all the springs, anchor pins, bushings and rollers, not just the shoe return springs. Spending a little extra money up front can save you valuable time and money later. When it’s time for that additional performance during stopping, the extra cost will seem inconsequential.
BRAKE DRUMS
Just because they fit doesn’t mean they’ll perform the same.
Never judge a drum solely by its fit. In the brake drum market, there are two basic types of drums – cast and composite. They differ in their ability to absorb and dissipate heat. A drum’s ability to provide satisfactory performance depends on its ability to dissipate heat.
Using different weight or types of drums on the same axle could result in unbalanced braking and improper functioning of automatic slack adjusters. Poor brake performance due to uneven lining and drum wear will occur.
THE PRESSURE’S ON
Make sure cam brake air chambers are the same size and type.
When changing cam brake air chambers, make sure all brake chambers on the same axle are the same size and type. In doing so, you will ensure proper brake balance. An unbalanced brake system could result in unacceptable lining and drum wear.
BRAKE REPLACEMENT PARTS
There are no unimportant brake replacement parts.
Brakes work as a system. When an original part is replaced by a “will-fit” part, performance of the entire system may be compromised. A will-fitter’s parts may be less expensive to buy initially, but they could cost you more down the road in downtime or reduced performance. So, don’t take a chance with something as important as your brakes. Replace brake parts with OEM-quality standard parts.
LONG-LIFE BRAKE KITS
Not all aftermarket kits are created equal.
Brake shoes, rollers, camshafts and shoe return springs for long-life brakes are specifically designed as a system for optimum brake performance. These components depend on each other to provide brake performance truck operators can depend on. Using non-OEM spec level components for maintenance or upgrading from standard to long-life brakes could result in unbalanced braking, poor brake performance or decreased lining life.
ANTI-LOCK BRAKING SYSTEMS
Anti-lock braking systems are not a cure-all for brake maintenance.
ABS effectively reduces wheel lock-up that can result in spinout and loss of steering control, which, in turn, helps minimize accidents, repairs and insurance costs. To achieve these benefits of ABS, make sure your foundation brakes are kept in adjustment and that you follow preventive maintenance guidelines to properly maintain your braking system.
CAM HEADS
They may look the same, but they don’t provide the same performance.
Two cam-head profiles may appear to be identical when viewed with the naked eye, but very small differences can be significant to the performance of your brakes. Each brake manufacturer designs its cams somewhat differently. Some are engineered to provide constant lift, while others promise constant torque. Conclusion? As with all brake components, use the proper replacement cam. Failure to do so can result in an unbalanced brake system and unacceptable lining and drum life.
AUTOMATIC SLACK ADJUSTERS
Never mix automatic slack adjusters on the same axle.
When it comes to replacing your automatic slack adjusters, always replace them with what was originally designed for the braking system. In other words, never mix two different brands of automatic slack adjusters on the same axle. This could result in uneven brake wear, unbalanced braking and poor brake performance.
IMPROVE BRAKE PERFORMANCE
Always make sure cam rollers are correctly lubricated.
The proper way to lubricate a cam roller is directly in the web roller pocket and not at the cam-to-roller contact area. If you do this correctly, you will avoid creating flat spots.
These flat spots adversely affect the brake adjustment, which may result in premature brake wear or reduced braking performance. The best time to change your cam rollers is when you reline. That will save you both time and money.
GIVE YOUR BRAKE A BREAK
Make sure your air brake valve crack pressures stay the same.
When you replace the valves in your air brake system, make sure that the new valves have the same crack pressure as those that are being replaced. Why? Because replacing a valve with one with a higher or lower crack pressure than the original valve can result in an unbalanced brake system and unacceptable lining and drum life.
REPLACING BRAKE LININGS
When it comes to replacing single or tandem axle brake linings, the best advice is: Replace one, replace them all.
Always replace the linings on both brakes of a single axle or all four brakes of a tandem axle at the same time. If you don’t, you could experience brake balance problems. Plus, not replacing a unit’s brake linings at the same time may contribute to uneven wear, reduced lining life, maintenance problems and drum cracking on your drive or trailer axles.
BRAKING TECHNIQUE
On a mountain descent, always snub, never drag your brakes.
When coming down a mountain with a fully loaded vehicle, it’s always best to use short 20- to 30-psi brake snubs in your descent. Why? If you drag your brakes, and your air system is not properly balanced, certain brakes will end up doing more of the work than others. This will lead to excessive temperatures and brake fade, resulting in increased stopping distance and shorter lining life.
HAND VALVES
Always give your hand valve a break.
Because trailer brakes are designed to work in conjunction with tractor brakes, it’s recommended that you not use the hand valve for braking, especially on long descents. If you overuse your hand valve, the trailer brakes do more than their fair share of the braking. This can result in excessive brake temperatures and shorter lining life on the trailer brakes.
