A B757 Captain noted an unsatisfactory brake pin on a walkaround which resulted in a lengthy delay while the brake was replaced. The worn condition had been noted 26 flight cycles earlier but deferred based on a company authorized monitoring program requiring only that its condition be rechecked after 30 flight cycles.

Narrative

During the preflight exterior inspection I noted the aft brake pin for the #3 forward tire was nearly flush. I advised maintenance and entered the discrepancy in ACARS. Maintenance did a good job of promptly responding and replaced the brake assembly. The required maintenance resulted in a 53-minute departure delay. I subsequently determined from Maintenance Control that the brake at issue had been inspected by Station Maintenance seven days earlier and was on 'recheck interval' status of the recently implemented 'Brake Wear Monitoring' system; which allows 30 flight cycles before further inspection. This aircraft had completed 26 of those 30 cycles when the brake had to be replaced. Clearly the new maintenance procedure fails to ensure that our aircraft are dispatched with serviceable brakes. This is the second event of unserviceable brakes I have encountered since the new procedure was implemented a few months ago. The other instance required the replacement of 3 brake assemblies prior to the scheduled inspection. Under this new maintenance procedure; pilots are effectively the only line of defense against our company aircraft flying with worn-out brakes. While I appreciate that the new brake monitoring system is intended to save costs; clearly it does not work. Further; the recent change to the normal operating section of the pilot's Flight Manual that requires an inspection of the brake wear pins did not prevent this entirely avoidable departure delay. This event undermines passenger confidence that our aircraft are airworthy at scheduled departure time. It also demonstrates that margins of safety are reduced when our maintenance procedures cut so fine a line in an effort to save costs.