Brake Adjustment Errors can Lead to OOS Violations or Worse
The following was published in CCJ's Air Brake Book, 11th edition, sponsored by Silverback HD. CCJ's Air Brake Book is a complementary industry resource, courtesy of our partnership with Silverback HD, the Technology and Maintenance Council and Commercial Vehicle Safety Alliance. You can download the entire Air Brake Book here.
During last year’s Brake Safety Week, 12% of the 43,565 commercial motor vehicles inspected were placed out of service for brake-related violations.
They’re called automatic slack adjusters for a reason, and the manufacturers that make them want to keep it that way.
Yet despite years of warnings, automatic slack adjusters (ASA) continue to be manually adjusted by technicians who may not know any better, or who may be eager to get a truck out of the shop and back out on the road.
Whatever the reason, it's a risky gamble that can result in costly out-of-service violations. During last year's Commercial Vehicle Safety Alliance’s (CVSA) International Roadcheck, brake issues led to 3,992 OOS violations in the U.S. the most by far of any category. Brake problems in the U.S. accounted for 24% of OOS violations during the September 2022 Roadcheck. Tires came in a distant second with 18.5% of total OOS violations.
With brake problems continuing to dominate OOS violations, experts advise following OEM guidelines on best practices for preventative maintenance which includes putting a halt to manually adjusting automatic slack adjusters. It can not only hinder performance, but also shorten component life.
“If a fleet is manually adjusting a slack adjuster regularly it can harm the longevity of the unit,” warned Chris Christiansen, warranty/technical services coordinator, Accuride Corporation.
“The reasons behind adjusting an ASA outside of a brake reline should be investigated such as alignments, bushing wear, wheel conditions, etc.,” Christiansen said.
Any drum or disc brakes that require manual adjustment at a time other than installation are not functioning properly and need to be serviced by a trained mechanic, noted Silverback HD Vice President of Operations Keith Roth. “Regular inspection to ensure that brakes are staying adjusted without human intervention is essential to any fleet maintenance PM,” he added.
Manually adjusting an automatic slack adjuster can not only lead to more brake problems down the road, it can also lead to accidents.
Following their mandated use on tractor-trailers in 1994 and trailers in 1995, the NTSB issued a scathing report in early 2006 condemning the practice of regularly adjusting ASAs. NTSB ruled an ASA adjustment had led to a runaway truck accident in Pennsylvania in 2003 that claimed the life of the driver and an 11-year-old child riding in a car that the dump truck had struck during its descent on a steep downgrade.