Every maintenance team tracks MTBF and MTTR. They're the universal language of reliability. But here's the problem: they're lagging indicators. They tell you what already happened, not what's about to happen.

If you want to prevent downtime instead of just measuring it, track these five leading indicators instead.

1. Schedule Compliance (Not Just Completion)

Most teams track whether PMs were completed. That's table stakes. The real question is: were they done on time?

Schedule compliance measures the percentage of PMs completed within their scheduled window, typically a 10% window. So a 30-day PM should happen between day 27 and day 33.

What good looks like: Above 90%. Below 80% means you're playing catch-up, and playing catch-up means machines are breaking.

2. PM to CM Ratio

Preventive Maintenance hours divided by Corrective (breakdown) Maintenance hours. This single number tells you whether you're running your program or your program is running you.

What good looks like: 60/40 or better (60% PM, 40% CM). Below 50/50 means you're reactive. Below 40/60 means you're in firefighting mode.

3. Backlog Aging

Not just how many work orders are open, but how long they've been open. A backlog of 200 work orders isn't necessarily bad if most are less than 2 weeks old. But if 50 of them are over 30 days, you have a prioritization problem.

What to watch: The percentage of backlog over 30 days old. Keep it under 15%.

4. Mean Time Between Failures by Equipment Class

MTBF is useful, but only when you segment it. A blanket MTBF across all equipment hides the problem children. Track it by equipment class, by criticality, and by age. You'll find patterns that the aggregate number buries.

Pro tip: Compare MTBF trends quarter over quarter. A declining trend on critical equipment is a leading indicator of upcoming downtime, even if the absolute number still looks okay.

5. Rework Rate

How many work orders require a follow-up within 7 days on the same equipment? High rework means either your PM procedures aren't thorough enough, or your technicians need more training (or both).

What good looks like: Under 5%. Above 10% is a red flag.

Putting It Together

Track these five KPIs for 90 days. Compare them quarter over quarter. The patterns will tell you where your maintenance program is heading long before a catastrophic failure does.

OpexMX builds all five of these into its analytics dashboard so you don't have to hunt through spreadsheets. See the dashboard in action.