Issues In Depth
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A technician repairs a Meritor air brake. With the new stopping rule, service providers can expect changes in 2011.
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1/25/2010
Braking News: New Regulations Could Spell Parts & Service Opportunities
By Steve Sturgess, Executive Editor
Changes in the works at the Department of Transportation could spell major opportunities for independent brake shops around the nation.
The finalizing of the long-awaited National Highway Traffic Safety Administration stopping distance rule, and the Federal Motor Carrier Safety Administration's new CSA 2010 safety rating system, both focus attention on truck braking systems.
The NHTSA rule mandates a shorter stopping distance for fully loaded tractor-trailers, down to 250 feet from 355 feet, and will require additional braking torque from the steer axle brakes.
CSA 2010 overhauls the whole motor carrier safety rating process with additional emphasis on roadside inspections. And what is the biggest out-of-service issue? Brakes, of course.
Stopping shorter
The NHTSA braking rule won't mean immediate changes for the parts and service provider. New three-axle tractors must meet the 250-foot rule starting Aug. 1, 2011. Two-axle tractors are not affected until 2013, and straight trucks and buses are not affected at all.
Meeting the new stopping distance will require bigger brakes on the front axle, since the drive axle brakes are already at the limit of the friction between the tire and the road surface. Stopping harder puts more weight transfer on to the front axle, so the bigger brakes can deliver more torque without the tires losing traction.
At one time, it was thought that shorter stopping distances would require a switchover to disc brakes. But brake makers now say drum brakes that are wider and larger in diameter than today's 4 x 15 drum will do the task economically. For instance, Webb Wheel Products says its recently introduced Vortex brake drums can do the trick without a weight penalty over today's standard drums.
It's still expected, however, that disc brakes will make a much bigger contribution to the repair business as they get a far wider acceptance in the market. There are already something like 150,000 disc brakes on America's highways as fleets have been evaluating their performance, longevity and driver acceptance.
Many predict that air disc brake will slowly become the norm on the front axle, with fleets being much slower to adopt them on drive or trailer axles.
Immediately after the new NHTSA regulation was announced in August, ArvinMeritor and Bendix both put out announcements that they already have drum and disc brakes, as well as combinations, that will meet the new standard.
With the proliferation of disc and drum combinations, it is imperative that repair shops be familiar with their operation and maintenance.
CSA 2010
The other rule change is the Comprehensive Safety Analysis 2010 program from FMCSA. It's a new way for the government to assess motor carrier safety. Many fleets are not yet aware of the impact it will have - but it is a change that will likely put some of them out of business.
Currently CSA 2010 is in field tests in half a dozen states, and it is expected that it will be fully implemented by the end of 2010.
Its mission is to reduce the number of commercial-vehicle-related crashes by targeting safety problems of motor carriers and - for the first time - drivers.
Unlike the previous SafeStat ratings, which were arrived at using safety audits, CSA 2010 will use a new Safety Measurement System that includes all safety-related violations found during roadside inspections - not just out-of-service violations.
These safety violations are weighted according to their relationship to crash risk, and the information is updated almost in real time. The target is to have every carrier and driver's safety profile updated every 30 days.
The new policy broadens the interventions and reaches far more carriers - and drivers - to alert both them and FMCSA of risky operations. The interventions will increase in severity and degree of interaction to correct the problems. No more will a carrier be able to pay the fine and then go on doing business as usual without addressing the safety problems.
This means opportunity for the independent brake service provider. Brake violations are the first example FMCSA uses in its CSA 2010 fact sheet when explaining the Vehicle Maintenance category, one of seven in its Behavior Analysis and Safety Improvement Categories (BASICs). Brakes out of adjustment, damaged or plain just not working could cause a carrier's safety compliance rating to get way out of control. That brings interventions and an order for a safety plan or even, ultimately, an operations out-of-service order.
Many fleets will need independent brake shops to be their brake safety service provider. And it starts with understanding how CSA 2010 will affect them and what they'll need to do to keep a clean bill of safety health. The brake shop should be the provider of the education about the impact of CSA 2010 and then be the provider of service and repair that keeps this aspect of the fleets operations completely out of the picture. (A good place to start learning about CSA 2010 is the web site http://csa2010.fmcsa.dot.gov.)
What is needed is a thorough brake maintenance program worked out in cooperation with participating fleets that keeps the brakes in top shape.
Brake maintenance
We've covered general brake maintenance in HDAJ recently. But that article dealt with the conventional S-cam brake and its associated hardware. For the bigger, wider drums expected to be used to meet the new stopping distances, procedures are not much different from what shops are doing today.
Disc brakes require a different approach.
According to the Bendix Service Data for its mainstream product, the ADB 22X, there are a number of preventive maintenance steps necessary to ensure that air disc brakes perform properly over their long lives.
For over-the-highway vehicles, the wear indicator on the caliper/pad assembly should be inspected every four months. As experience grows with the brakes, this interval can be changed so that the checks are made four or five times between pad changes. More extreme duty cycles should be inspected more frequently initially so that the same interval between inspections and pad changes can be established.
At the same time, the discs must be inspected. In line-haul applications, little interaction can be anticipated, but in severe service some cracking may become apparent. Understanding how much cracking and other surface damage can be tolerated is important for these inspections.
A service interval should be established for checking the running clearance between pads and rotor, and for correct adjuster function. These procedures vary and can be found in the service literature from the brake supplier. Caliper travel should also be checked. This may be done on every pass through the shop. Techs should check the sliding calipers to ensure they slide freely on the pins or guide sleeves. This ensures pads press evenly on both sides of the rotors and wear evenly when the brake is applied.
On the Bendix calipers, tappets and boots and the general appearance of covers, caps hoses and brake exterior should be examined during this check. The same applies to the appearance and general condition of seals on other makes of disc brake.
If there's any binding of the slide or uneven clearance, or too much clearance, a wheels-off inspection should be made.
Disc brake Pad and rotor change
If optional electrical wear indicators are present, a dash light will illuminate or an alarm buzzer sound to indicate a brake issue. If this happens, or when the indicators on calipers and pads align, the pads need checking. If the friction material on the pads is worn down to 2 mm, according to ArvinMeritor, they are due for replacement. Even if the pads measure more than 2 mm, if there are significant chunks of material missing, replacement is required. And pads should be replaced on both ends of an axle.
This is obviously a wheels-off procedure, and the pads are replaced according to the manufacturer's service literature. In general, this means removing the pad retaining clip, backing off the adjuster mechanism and withdrawing the old pads. This is a very quick operation and, depending on what is included in the new pad kit, pads and retainers, some seals, etc are discarded.
Technicians should be protected from brake dust during the procedure. They should be sure to wash hands after handling brake components certainly before eating or smoking. While not specifically carcinogenic, brake dust is still a dangerous irritant.
(It's worth noting that asbestos is no longer used in brake products -- unless perhaps they are off-brand or counterfeits from overseas.)
In Meritor's case, the recommendation is to remove the old pads, back off the adjuster until the outboard pad can be inserted, push the caliper across until the pad contacts the rotor, and continue to back off the adjuster until the inboard pad can be installed.
The adjuster should be tightened till pads are on the rotor, than backed off for the appropriate running clearance.
Obviously, the rotor should have been inspected before reassembly commences so any extensive damage can be dealt with. Bendix says small radial cracks no more than 1.5 mm wide and 1 mm deep are OK, providing they don't extend more than 75 percent of the disc face. Any crack that goes to either edge of the rotor means the rotor should be discarded. Circumferential grooves are acceptable, providing they are no deeper than 1.5 mm.
Changing out a rotor is no more time-consuming than a drum, once the wheel-end is exposed. Obviously the caliper has to be removed to get the hub off, and there is always the danger of damage to the seals. The rotor in all but the severest service applications will outlast the periodic maintenance for wheel-end bearings and seals, so this should not be an issue.
Adding up
When spec'ing air disc brakes, fleets look to the maintenance savings of disc brakes to cover the extra cost of the option. Of course, duty cycles determine what those savings may be and whether there is an economic case to be made for the new technology.
Nevertheless, the brake manufacturers do anticipate a gradual acceptance of the disc brake for the performance and maintenance benefits that enhance a fleet's safety performance and likely safety rating.
If a fleet makes a decision to adopt air disc brakes, the independent brake shop should become the maintenance adviser to the fleet, with trained technicians and service programs that provide a much faster and better brake job when, after many more miles, service becomes necessary.
From the January/February 2010 issue of Heavy Duty Aftermarket Journal.
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