The new National Highway Traffic Safety Administration (NHTSA) stopping distance reduction requirement goes into effect soon. It will have a major impact on the maintenance of truck tractor brakes.
At the Heavy Duty Aftermarket Week in January, a panel of technical experts discussed the impact of proposed stopping distance regulations. The experts agreed that while fleets may experience longer lasting brakes due to the advantages of wide brake configurations, both fleets and parts distributors may have inventory challenges as a result of the new stopping distance regulations.
The final rule will require 20 to 30 percent reduction of stopping distance at 60 mph for new air-braked tractors under all load and system conditions. The new regulation initially will impact new truck tractors, approximately 10 percent of the heavy duty population. The other 90 percent is a mix of truck tractors with various levels of brake maintenance.
Options: Drum versus Disc
The current standard drum front and rear brakes will not perform to the standards in the new regulation without some changes in the friction material used. This will result in increased maintenance cost for fleets due to higher wear of brake system components, so it is probably not a viable option.
The large/wide-drum standard-drum drive appears to be a likely alternative. The performance exceeds the new stopping distance standard, with a distance of 211 feet compared to the requirement of 248. Other benefits include better lining/drum wear due to lower brake operating temperatures and no change in maintenance practices to service brake system.
While there is an increased cost over standard brakes, better stopping distance can result in less property damaged due to reduced impact velocity and reduced liability and insurance costs.
Foremost among the impact of the wide-drum brake option for fleets is brake balance issues between truck and trailer since trailer brake will be unchanged. The wide brake package may cost more than the current standard brake configuration.
Fleets also will have to stock multiple brake drums for both steer and drive axle applications depending on brake size, axle and hub configuration.
The primary concern with air disc brakes is maintenance. Certain disc brake components will require regular checks for wear and periodic, routine replacement: pads/springs, rotors, slide pins/bushings and chambers.
Under these new rules the quality of replacement components is more critical as ever. Real world liabilities exist for distributors and fleets using unsafe or inferior linings.
Conventional wisdom that "You get what you pay for" is true of friction material, especially with regards to service wear life. In testing of these materials, the lower cost compliant materials offered less service life, according to the panel of experts at HDAW. Low cost products may have offer short-term bottom-line improvement, but the net result for a fleet operator can be increased overall cost, and vehicle downtime.
Fleet maintainers are urged to deal only with reputable and trusted suppliers and ask for supporting dynamometer data on products.
It's Just the Beginning
While NHTSA is only addressing truck tractors in this rule, the agency has indicated it may address the braking performance of other types of heavy vehicles (trailers, straight trucks, buses, etc.) in future rule making. Implementation is expected in 2009 for typical highway tractors (80 percent) and in 2011 for special configuration tractors (20 percent).
The real-life impact from these regulations will have lessons to be applied as new regulations are proposed and opened for public comment.
The full presentations from HDAW brake panels are available online at the HDMA Web site, http://hdma.org//events/eventdetail.php?eventId=324. DVDs of the presentation also are available for purchase—details are on the Web page.