With pedal pulsation complaints becoming a key concern for motorists, it’s important that technicians are as thorough as possible when diagnosing the root cause of the problem. Most technicians are familiar with the role that rotor runout plays in pedal pulsation, yet the hub and wheel bearing can also play a key role in prevention.
“In an ongoing effort to achieve better fuel economy and vehicle handling, the automakers constantly strive to reduce unsprung weight,” said Jay Buckley, the Bendix Brakes Answerman and Honeywell Consumer Products Group Training Manager. “This means that extra attention is needed when servicing and machining rotors.”
Most importantly when servicing a rotor, technicians should be sure to clean all rust and corrosion from the hub and rotor mating surface since it is impossible to have the correct rotor runout when it is mounted on a dirty hub. Another often overlooked procedure according to the Bendix Brakes team is checking the hub flange for runout, and checking the hub bearing for play. A loose or worn wheel may eventually lead to pedal pulsation.
It is also important for technicians to inspect the wheels. Many aluminum wheels experience an extraordinary build up of dissimilar metal corrosion on the face that stacks up against the rotor hat. If the corrosion is not removed, it can distort the rotor friction face when installing the wheel. This distortion could lead to pedal pulsation a few thousand miles down the road. Some quick work with a wire wheel should solve the issue. Since most vehicles now use aluminum wheels, technicians should make cleaning this surface a part of every brake job.
Lastly, technicians should always make sure that the wheel lug nuts are torqued to the vehicle manufacturer’s recommended specifications. Improper torquing of the lug nuts can increase pedal pulsation as well.