It isn’t uncommon for techs to ask if new rotors should be machined. The answer, according to Bendix Answerman Chuck Kennedy, is a resounding no: machining new rotors is an unnecessary step that could actually lead to more problems that might not have occurred otherwise.

“New rotors are machined on accurate and costly computer numerical controlled (CNC) machines,” said Kennedy. “The use of a CNC machine minimizes run-out and stack-up tolerances from multiple operations such as those that would be needed on a bench lathe. It is highly unlikely that the average shop has this type of CNC equipment at their disposal.”

According to Kennedy, new rotors should merely be washed thoroughly with soap, water and a stiff brush and then installed. He also recommends checking old rotors to determine the source of run-out — a step that is often overlooked. Checking hub assemblies and axle flanges for run-out may help determine what will happen after a new rotor is installed on the vehicle.

“New rotors cannot fix a run-out issue, but if a thousandth or two of run-out on a rotor is clocked to offset a small amount of run-out in a hub, this can help give the rotor extended life and do a lot to keep pulsation issues from arising after a short time,” said Kennedy. “Using quality brake components means you won’t have to worry about the fit or finish, and you can be sure your concerns are handled should any issue ever arise.”