The following was published in CCJ's Air Brake Book, 11th edition, sponsored by SilverbackHD. CCJ's Air Brake Book is a complementary industry resource, courtesy of our partnership with SilverbackHD, the Technology and Maintenance Council and Commercial Vehicle Safety Alliance. You can download the entire Air Brake Book here.
A balanced brake system is one in which all the vehicle’s brakes apply and release at about the same time, with each brake developing the appropriate braking force for its respective load.
Visualizing this concept, it’s not hard to imagine the safety and maintenance problems that imbalanced brakes can cause for a commercial vehicle.
If a tractor, for example, brakes more aggressively than the trailer it is towing, uneven brake wear will be the most obvious consequence as the linings on the hardest-working brakes will wear faster than the brakes not doing their fair share of the work. Worse, this condition could lead to a trailer bumping into the braking tractor, jackknifing or unintended panic stops as brakes lock up.
The frequency of brake imbalance situations has decreased somewhat thanks to improved brake technology. Today’s brake systems are comprised of a myriad of components that must all work properly and in the correct sequence to guarantee safe, efficient stopping. If just one of those components fails to perform, the vehicle’s brake system will begin applying in an unsynchronized manner.
Brake imbalance is an early warning sign that a brake system is not functioning like it’s supposed to. Torque imbalance, pressure imbalance and different tire sizes are all common problems that can lead to a brake imbalance problem.
Each of those circumstances can be complicated further by the extreme temperatures under which foundation brakes operate. For many technicians, tracking down the source of a brake imbalance problem can be like a forensic investigator trying to figure out a crime scene. Many possibilities have to be examined and discarded before the culprit is identified.
