G. Wheel PM interval
Recommended cadence: swap wheels every 36 months
At current fleet usage, a 36-month caster replacement cycle has the lowest total cost per cart per year — the schedule pays for itself by displacing dedicated reactive trips. Adjust usage and PM effectiveness below to stress-test the recommendation.
Baseline wheel events
Measured0.054 / cart / yr
144 TTM tickets ÷ 2,669 carts, scaled by usage.
Recommended interval
Estimate36 months
Cheapest total: $71/cart/yr vs $31 today.
Est. fleet savings
Estimate-$107,873
Across 2,669 deployed carts, per year.
PM-addressable share
Measured44%
Share of wheel tickets tagged as wear or calibration.
Assumptions you can tune
The model is only as good as its inputs — move these to reflect your read of the fleet.
1.0× = fleet-average failure rate. Higher for busier stores (Kroger, Schnucks).
How much of the wear-driven share a scheduled swap actually catches.
Cost per cart per year, by interval
Green = scheduled PM spend. Gray = residual reactive spend. Line = total. The low point on the line is the sweet spot.
- Scheduled PM
- Residual reactive
- Total
Full scenario table
Assumes 4 wheels per cart · $33/wheel bundled PM · $566/event reactive.
| Interval | PM $ / cart / yr | Residual events | Reactive $ / cart / yr | Total $ / cart / yr | Fleet total / yr | Vs baseline |
|---|---|---|---|---|---|---|
| No PM (today) | $0 | 0.054 | $31 | $31 | $81,504 | — |
| 6 months | $264 | 0.035 | $20 | $284 | $757,431 | -$675,927 |
| 12 months | $132 | 0.035 | $20 | $152 | $405,123 | -$323,619 |
| 18 months | $88 | 0.041 | $23 | $111 | $297,250 | -$215,746 |
| 24 months | $66 | 0.044 | $25 | $91 | $243,313 | -$161,809 |
| 36 monthsrecommended | $44 | 0.048 | $27 | $71 | $189,377 | -$107,873 |
Chart data table
Same numbers as the chart, for the record.
Modeled catch rate — the share of wear-driven wheel failures caught before they become a ticket, as a function of interval. Longer intervals catch less; below annual there's diminishing return.