Are Air Disc Brakes Worth It?

 

Our first experience with disc brakes in the 1980s wasn’t successful. The materials and designs weren’t ready for the challenges, leading to their unreliability. However, the modern iterations of air disc brakes (ADBs) have significantly improved, prompting fleets to reconsider their use. The ATA’s Technology and Maintenance Council revisited this discussion at their annual meeting in New Orleans, concluding that while ADBs are

worth the switch in many cases, they aren’t a universal solution for all fleets.

Uptake is Improving

The re-introduction of disc brakes brought substantial improvements. Modern ADBs feature internal actuators and automatic adjusters, with mechanisms sealed from the elements, including the slide pins. These upgrades, along with better rotor designs, have enhanced their heat management and crack resistance.

Early adopters of ADBs in North America included emergency vehicles and fuel haulers, valuing the brakes’ high-energy stopping power and added safety margin. Over the past five years, there has been a significant increase in ADB adoption among various fleets. According to Brian Andrews, engineering manager at Cummins-Meritor, the adoption rate for tractors rose from under 5% in 2011 to about 50% by 2023, while trailers saw an increase from less than 5% to over 15% in the same period.

Several factors have driven this growth, including the National Highway Traffic Safety Administration’s revised stopping distance rules. Meeting Phase Two requirements for heavier trucks often necessitated ADBs on steer axles to maintain stopping distance margins. Additionally, improvements in design, cost, and weight, along with increased volumes, have made ADBs more cost-effective.

Advantages of ADBs

Air disc brakes offer several benefits over drum brakes. One key advantage is their resistance to brake fade during repeated hard stops. Unlike drum brakes that lose effectiveness as the drum expands away from the lining when heated, ADBs improve as the rotors expand into the pads. This consistent performance can make the difference between a crash and a near-miss.

Drivers prefer ADBs for their passenger-car feel and enhanced safety margin. Additionally, trucks with ADBs often pass CVSA Level 1 inspections more easily, leading to fewer citations and better CSA scores.

From a maintenance perspective, ADBs have a lower total cost of ownership (TCO), especially with short trade cycles. They require less frequent servicing, and pad changes are quicker than replacing drum brake linings. Some fleets report going three to four years without major brake maintenance beyond pad changes.

Challenges with ADBs

Despite their advantages, ADBs come with challenges. Inspecting the friction material is more difficult, often requiring borescopes or pad-wear sensors to assess pad thickness accurately. Technician training is crucial, especially for trailer ADBs, to ensure thorough inspections and maintenance.

Corrosion of ABS tone rings remains an issue, but manufacturers are developing new designs and coatings to address this. In abrasive environments like construction sites, dirt and debris can shorten pad and rotor life, although shields can help mitigate this problem.

Fleet Experiences

Fleets like GP Transco and Maverick have reported positive experiences with ADBs. GP Transco’s maintenance director, Alex Gorno, highlighted the benefits of ADBs with their short trade cycles, noting reduced maintenance costs and fewer brake repairs. Maverick’s Brent Hilton shared similar insights, emphasizing the importance of staying on top of preventive maintenance to avoid costly road failures.

 

Source:

https://www.truckinginfo.com/10222625/are-air-disc-brakes-worth-it