Issued in July 2009 by the National Highway Traffic Safety Administration (NHTSA), new tractor braking standards are set to take effect in August of this year. To meet and exceed the rule’s more stringent stopping distance requirements, braking system suppliers have been working in close cooperation with vehicle manufacturers to develop and refine effective solutions for fleets.
“Vehicle OEMs will define what’s appropriate,” says Duane Evans, technical sales manager for Bendix Commercial Vehicle Systems, “so we have been working with them for nearly five years to provide system-based solutions to stopping distance regulations. For all types of vehicle configurations, the goal is to enable stopping distances that exceed the new standard. What fleets should understand is that when they purchase a new vehicle after August of this year, it will be compliant with the new regulations.
“The development effort involves more than the foundation braking system,” Evans continues. “It also includes wheelbase, axle weight rating, tire size and type and electronic system integration issues. We encourage fleets to talk to their vehicle manufacturers and braking system suppliers so everyone understands the needs of their operations.”
Using current products
While vehicle builders are responsible for making sure their products are compliant with new regulations for shorter stopping distances, notes Joe Kay, chief engineer, brakes at ArvinMeritor, many existing brake system products will be available to meet those needs. “For over three years, in anticipation of the new regulations, we have been working on a reduced stopping distance program,” he says. “As a result, we have current products that can meet the new requirements with an additional 10% margin.
“In addition,” Kay continues, “larger brakes will not be required in all cases. While this is particularly important for weight sensitive customers, transitioning to larger brakes can provide some advantages, including increased lining volumes that drive longer service intervals, and lower operating temperatures that help reduce fade and improve performance.”
In all likelihood, there will be an increase in the cost of tractors built after Aug. 1, 2011 to cover the enhanced drum brakes that will be required to meet the new regulations. While it remains to be seen how much more compliance with the new standards will cost, it could make considering air disc brakes a potentially worthwhile long-term investment. “Air disc brakes can be utilized to meet the new regulations,” Kay states. “Manufacturers are poised to have a full array of air disc brake products available for fleets.”
| Issued in July 2009 by the National Highway Traffic Safety Administration (NHTSA), new stopping distance standards are set to take effect for three-axle tractors with a Gross Vehicle Weight Rating (GVWR) of 59,600 lbs. or less built after Aug. 1, 2011.
The reduced stopping distance requirements specified by NHTSA mandate that a tractor-trailer traveling 60 MPH must come to a complete stop in 250 ft., a reduction of about 30% over the previous standard of 355 ft. For some severe service tractors, the new stopping distance requirement will be 310 ft. and the ruling requires that all heavy-duty tractors must stop within 235 ft. when at their Lightly Loaded Vehicle Weight. The new stopping distance regulations are going to be phased in over four years beginning with the 2012 models manufactured after August of this year. Two-axle tractors and power units with a GVWR above 59,600 lbs. must meet the reduced stopping distance requirements by Aug. 1, 2013. Early compliance is permitted, and the rules apply only to new tractors and do not cover existing vehicles, trucks, trailers or buses. |
Two to one
“When it comes to air disc brakes for tractors and trailers, cost is one part of the equation,” says Gary Ganaway, director of marketing and global development at Bendix Spicer Foundation Brake LLC. “Other factors for fleets to consider are safety related, such as the faster response times and shorter stopping distances with air disc brakes. For fleets with experience with air disc brakes, it is also apparent that servicing times are considerably shorter and service intervals are generally longer. A rule of thumb in most applications is a factor of two to one.”
Another specification choice for fleets using cam brakes is for automatic slack adjusters. Required by law on vehicles equipped with air brakes, the adjusters keep the lining to drum clearance at an optimized distance. As such, the length of the slack adjuster’s lever is part of brake sizing and application specifications. Variations can create problems, including dragging brakes and allowing air chambers to go out of their allowable operating range.
“When replacing automatic slack adjusters, always try to use the OEM part,” says ArvinMeritor’s Joe Kay, “and never mix products on an axle. Each manufacturer’s product adjusts at a different rate, so that may lead to vehicle stability problems. Slack adjusters work well if properly installed and maintained, and as long as the entire foundation brake system is in serviceable condition.”
Compromising performance
In the event that any brake system component needs replacing, and especially for replacement brake linings, the manufacturers advise using only OEM quality parts. Replacing with less expensive “will-fit” items, they say, can compromise the performance of the entire braking system, and can ultimately cost more.
Especially important, notes Tom Runels, engineering manager, foundation drum brakes at Bendix Spicer Foundation Brake, is for fleets to consider only OEM replacement friction materials. “Those are what we certify and are always the best replacement choice,” he says.
“In the aftermarket, where a variety of competitive linings that meet our standards are available, we have found anomalies that we didn’t see in original products,” Runels adds. ”Beyond stopping capability, for example, there may be noise and vibration issues with linings that are not held to the same performance standards as original equipment.”
Little change
Both major brake system manufacturers do point out that there will be very little, if any, change in brake service practices once the new regulations take effect. As a result, technicians will not have to be re-trained and parts inventory will carry over to the new drum brakes. Still, they advise that regular preventive maintenance schedules should be maintained, and if transitioning to longer life linings, it is even more important not to back off on inspections.
“At all times,” says ArvinMeritor’s Joe Kay, “remember that brakes are designed to work as a system. It is that development by OEMs and braking system manufacturers that is a key to success, and to meeting the safety goals of the new stopping distance regulations.”
Balanced tires equal better performance
Better vibration reduction leads to extended take-off mileages, which means fleets enjoy more time with tires on vehicles, more time between tire purchases, and money in their wallets. The world is waking up to the dangers of lead and moving toward lead-free balancing materials.
Internal balancing compounds, according to IMI, creators of EQUAL, are an environmentally safe, lead-free solution to ride improvement. The latest instructional materials from Technology & Maintenance Council of the American Trucking Associations (Radial Tire & Disc Wheel Service Manual) and the Tire Industry Association (Commercial Tire Service Manual, Module 14) recognize the use of balancing compounds.
IMI states that EQUAL is specially formulated plastic particles that come in an easy-to-use drop-in bag, which takes seconds to install while mounting the tire. The company says it categorically outperforms spin balancing by delivering self-adjusting balance and vibration dampening through the entire tread life of the tire (truck tires can lose 20 lbs. or more of tread rubber while in service, affecting balance requirements).
