We all have those days when it seems like we’ve unknowingly triggered an avalanche of problems. By dinnertime, we’re mentally backtracking through the day, trying to figure out what exactly caused us to lose our equilibrium and how to prevent future similar messes from occurring.
If something on a truck breaks, snaps or wears, it’s obvious that the part needs to be repaired or replaced. But sometimes it’s not enough to just replace the broken or worn part; you have to look beyond the immediate damage to find the cause of it so that the replacement part doesn’t meet with the same fate.
Brake balance is one such issue that calls for thorough causal investigation so as to prevent future damage. For example, if friction material on a brake shoe is worn, it’s not enough just to replace the material because if the imbalance is not corrected, the new friction material will wear rapidly.
When it comes to brake balance, things are not always what they seem. Dennis Griffin, product manager, commercial vehicle friction and brake hardware, Federal-Mogul Corporation/Abex Brake Products, cautioned that, “Balancing the friction material is very important. If you have a low-grade economy brake lining on one axle and a premium lining with superior stopping power on the other axle, then the premium lining is going to wear faster because it is doing most of the work.
“You may mistakenly think the premium lining is not as good as the economy lining because it wore out faster when in reality, the opposite is true. It wore out faster because it was the better lining,” he said.
Before jumping into the costly consequences of not thoroughly examining uneven friction wear, it’s important to establish exactly how brake balance is defined.
“Brake balance on a vehicle simply means that the brakes at each wheel are applying and releasing at the same time, and that each brake is sized to provide the correct amount of braking force for the static weight being carried by its axle,” explained Prakash Jain, director, JV and licensees, brakes, ArvinMeritor, Inc.
“If brakes are not balanced, there are potential negative consequences on brake temperature distribution, lining wear distribution, drum cracking potential and ultimately, on the vehicle maintenance cost,” Jain said.
Some may say that it’s not essential to have all the brake friction material on all the brakes wear at a consistent, even rate. After all, if one axle wears faster, it means that another axle has not experienced as much wear and will last longer, thus balancing the cost of material repairs. But the consequences of brake imbalance can extend far beyond simply replacing brake friction material at a higher rate.
It’s vital to remember that every time a customer brings his truck in to be serviced it is a costly affair, both in service fees and vehicle downtime.
“The costs of unscheduled brake replacements include more than just the price of the parts,” said Griffin. “Downtime that results in lost revenue and labor costs are the greatest economic loss factors of unscheduled repairs.”
According to Chuck Eberling, principal engineer, vehicle system integration modules, Bendix Commercial Vehicle Systems, “If brake wear becomes dramatic enough, it can manifest itself as tire wear on the more aggressive axle. The things impacted by brake imbalance are the tires, the friction material itself and the amount of servicing that’s required for those items.”
Eberling went on to further explain how severely brake imbalance can affect component wear. “If all axles on a truck are under the same weight ratings and have the same brake output, a 2 psi imbalance can lead to a 200
