Experiencing brake fade is never a fun scenario for any driver, and nobody wants to use those runaway truck ramps built off to the side of long, steep roads. So, how does brake fade happen, and what are the best ways to avoid it?
“Brake fade happens when the driver reaches the limit of the braking system,” says Greg Dvorchak, Engineering Supervisor – Applications, Wheel Ends and Braking systems at Hendrickson. “For instance, drum brake fade occurs when the drum becomes superheated, causing the drum to expand and preventing the brake pad from making adequate contact with the drum. This can result in the truck or trailer’s inability to successfully apply the appropriate friction to slow down or even stop the vehicle.”
Aggressive or prolonged braking in hilly areas can cause brake fade, meaning drivers may experience a “spongy” brake pedal feel. Dvorchak says that while brake fade is commonly known to occur in drum brakes, it can also happen in disc brake systems.
“Brake fade can present itself in one of two ways: either mechanical or chemical fade. Mechanical and chemical fade is commonly seen in drum brakes, especially in aggressive braking environments, which may cause the drum to superheat and expand, preventing the brake shoe from making adequate contact with the drum,” he says.
“Air disc brakes, on the other hand, mostly experience chemical fade when the pad material breaks down. As the pads deteriorate, they release chemicals that create a vapor barrier, requiring increased brake pressure to slow the vehicle down. In testing of lining formulations, it has been found that lining recipes play a large role in chemical fade for both drum and disc brakes. In the coming years, this could pose a challenge to disc brake friction material suppliers as the next generation copper compliance regulations are released.”
A Light Touch
Dvorchak says that advancements in braking technology have come a long way toward keeping drivers on the road, but proper technique is just as important when it comes to avoiding trailer brake fade.
For instance, locking up the brakes at the top of a mountainous descent is not a great strategy for successful stopping. Instead, slowing to a safe speed, letting off the brakes before things heat up too much, and reapplying when the driver has sped up about five mph can help maintain control.
Drivers can also employ engine braking, which helps absorb engine power to slow the vehicle down. This avoids unnecessary strain and can work in conjunction with the on-off method described above.
However, there’s still one tip that’s even more effective for preventing trailer brake fade.
Preventative Maintenance
Dvorchak says that no matter what brakes are being used, the best prevention is for fleets to follow through with trailer inspections before every trip and keep up with regular service intervals.
“Maintenance technicians should regularly check the drum or rotor for cracks and signs of wear and verify accurate brake stroke is in place. The trailer’s duty cycle and operation conditions help determine the intervals at which maintenance should be performed. Dynamics like average length of haul, application, terrain, driver patterns, and truck-trailer equipment combinations are important factors to consider when determining intervals at which components like brake linings should be replaced,” Dvorchak says. “Hendrickson recommends that all maintenance is done within the interval standards based on the trailer’s application.”
Dvorchak adds that technicians should also consider the importance of truck and trailer balance.
“Hendrickson has approved a variety of brake combinations between the truck and trailer, including mixed drum and disc combinations, but the incorrect application could add to the possibility of brake fade.”
Ensuring all brakes are in good shape and addressing any issues ahead of a trip is the best way for fleet managers to set their fleets up for success.
