NHTSA To Research Lining Ratings
Here's your chance to contribute.
JIM WINSOR
EXECUTIVE EDITOR
At long last, the National Highway Traffic Safety Administration is about to do some research to determine a rating system (or systems) for heavy truck brake linings. It's been a long time coming. The American Trucking Assns. petitioned NHTSA about 15 years ago to work out a rating system for aftermarket truck brake linings. Nothing happened until this year when $300,000 was specifically included in NHTSA's budget for this project.
Here's a quick refresher on brake lining regulations: New truck, tractor and trailer brakes, which includes linings, must comply with FMVSS 121. Most of us think of "121" as the anti-lock air brake rule. Actually, ABS is just a small part of a very detailed standard covering the technical and performance side of air brakes. But one thing it doesn't cover is heavy duty aftermarket (replacement) brake linings.
We all know, perhaps the hard way, that buying replacement linings with a different friction level can make those linings more or less aggressive than the ones that the vehicle manufacturer put on at the factory. In the case of tractors and trailers, a change in the coefficient of friction on the tractor or the trailer can significantly affect brake performance and throw a rig out of brake balance with one half of the rig doing more braking than the other half.
The Technology and Maintenance Council of ATA developed a Recommended Practice (RP 628A) as an interim guide to lining friction ratings at 40 psi of brake application pressure. It's a voluntary system where lining suppliers certify lining friction by lining part number. It's been a good stopgap but not all inclusive because a number of lining suppliers choose not to spend the money for dyno tests and friction certification.
So, what's NHTSA trying to do? In a nutshell, develop a new rating system or systems that brake engineers can agree to, that fleets and others can understand and that are accurate and useful. A tough job for sure.
Starting point is getting fleet and other heavy truck user input. The research contractor is Oak Ridge National Laboratory, a well-known name. At the fall meeting in Charlotte, on Oct. 17, TMC will spend the day reviewing the above issues, fleet experiences and fleet maintenance executives' ideas of what they want in a NHTSA-mandated rule.
In developing ratings systems, do fleets want:
• A simple way to find out the original lining friction when the vehicle was built and a way to buy this same friction as replacement?
• A rating system for lining wear?
• A rating system for performance by gross axle-weight rating?
• A separate rating system for disc brake pads?
• A separate rating system for heavy duty hydraulic drum brakes? Another one for hydraulic disc brakes?
• Rating systems based on brake dynamometer test procedures? And if so, can the industry accept one or more dynos for testing without necessarily having identical repeatable results (one of today's problems)?
If you want to have your thoughts heard, send them to Dr. Peter J. Blau, Oak Ridge National Laboratory, P.O. Box 2008 --M/S 6063, Oak Ridge, TN 37831-6063. Fax him at: (865) 574-6918 or email him at: blaupj@ornl.gov
Be a contributor to this important project.
