A Maintenance Manager reports he mistakenly deferred a # 7 Main Gear brake wear on a B757-200 during an aircraft turn. He had not adequately read the Maintenance Manual 32-41-10 requiring a brake change because the aircraft was already at a Maintenance Station.

Narrative

Overheard of an impending brake replacement on aircraft at the gate. Aircraft was being prepped for departure that night. Crew reported that the # 7 brake assembly was near ultimate wear limit. AMT attending to the problem was readying for a brake replacement. I arrived to the gate with the Lead AMT to check on the situation. Both the Lead and I noted that the wear pin on the brake was not flush and at least a 1/64' existed. We went to the gate office and inquired about the need for a brake change. The AMT was visibly upset that we questioned if the condition could be deferred and left the decision to me. The Lead AMT went to discuss the situation with the flight crew. I quickly reviewed Table One of (Maintenance Manual) MM 32-41-10 and noted a ten cycle fly back for brake replacement. I contacted Maintenance Control and was given the OK to defer the brake for ten cycles. I created a deferral and aircraft was dispatched. Aircraft was a planned overnight in ZZZ and the brake was replaced after one flight. The following night it was brought to my attention the details in the AMM specifications required our Station to replace the brake. The Maintenance Program for checking brake wear has changed; in lieu of checking brake wear on routine Service Checks; the program has created callout directives to check brakes at required intervals. As the wear increases on the brake and the pin gets shorter; the brake wear check intervals are reduced. At one-eight of an inch [remaining pin wear] at designated brake change stations; with parts; the brake requires replacement. Unfortunately there was a breakdown in this process as the brake should have been on reduced intervals which would have required more frequent checks to prevent finding a brake in this manner by a flight crew. I erred by not slowing down and going over the details of the AMM. Prior to the change in the Maintenance Program; this was the normal handling of brake wear checks and limits.