From grimoire
Measures tread depth, interprets wear patterns, calculates remaining safe life, and determines tire replacement based on NHTSA safety thresholds and vehicle regulations.
How this skill is triggered — by the user, by Claude, or both
Slash command
/grimoire:calculate-tire-wear-assessmentThe summary Claude sees in its skill listing — used to decide when to auto-load this skill
Measure tread depth, interpret wear pattern type, calculate remaining safe life, and determine whether tires require immediate replacement using NHTSA safety thresholds and systematic wear pattern diagnosis.
Measure tread depth, interpret wear pattern type, calculate remaining safe life, and determine whether tires require immediate replacement using NHTSA safety thresholds and systematic wear pattern diagnosis.
Adopted by: NHTSA (National Highway Traffic Safety Administration) mandates minimum 2/32" tread depth in the US; EU regulations require 1.6mm (≈2/32"). AAA recommends proactive replacement at 4/32" for wet-weather safety. Fleet operators (UPS, FedEx, airline ground vehicles) use systematic tire assessment schedules to prevent blowout-related incidents. Impact: NHTSA data shows tires contribute to ~664 fatal crashes annually in the US — most due to worn tread, under-inflation, or damage. Wet stopping distance at 4/32" tread is 50% longer than at 8/32"; at 2/32" it doubles relative to new tires. Beyond safety, misidentifying the cause of uneven wear leads to repeat failure — worn tires are a symptom; the root cause (alignment, inflation, suspension) must also be corrected.
Tread depth gauge (most accurate): insert probe into tread groove at the shallowest point; read in 32nds of an inch (US) or mm (EU).
Penny test (emergency check): insert a US penny (Lincoln head down) into the tread. If you see the top of Lincoln's head, tread is ≤2/32" — replace immediately.
Quarter test: insert a US quarter (Washington head down). If you see the top of Washington's head, tread is ≤4/32" — replace soon; wet-weather performance is significantly compromised.
New tire tread depth: typically 10/32" to 11/32" for passenger; 14/32" for light truck.
Measure at 3 points across the tread width (inner, center, outer) and at 4 locations around the circumference. Record all measurements.
| Wear pattern | Diagnosis | Root cause |
|---|---|---|
| Center wear (middle worn, edges fine) | Over-inflation | Reduce to door-jamb placard PSI |
| Edge wear (both edges worn, center fine) | Under-inflation | Inflate to placard PSI; check for leaks |
| One-sided edge wear | Camber misalignment | Front-end alignment service |
| Diagonal/feathering (waves across tread) | Toe misalignment | Alignment service |
| Cup/scallop (high-low spots) | Worn shocks/struts | Replace shocks or struts |
| Patch wear (flat spot) | Wheel lockup / hard braking | Check brake system; rotate or replace |
Never replace tires without correcting the root cause — new tires on a misaligned vehicle will wear identically.
Estimate remaining mileage based on current depth vs. replacement threshold:
Remaining tread = current depth (32nds) − replacement threshold (4/32" recommended)
Wear rate = (new depth − current depth) / miles driven
Remaining miles = remaining tread / wear rate
Example: new at 10/32", now at 6/32" after 20,000 miles:
Wear rate = (10 − 6) / 20,000 = 0.0002 per mile
Remaining to 4/32" = (6 − 4) = 2/32"
Remaining miles = 2 / 0.0002 = 10,000 miles
Note: wear rate is not linear — the last 2/32" wear faster if driving conditions are unchanged.
Tread depth alone doesn't determine replacement. Also inspect:
Tire pressure affects tread wear directly (Step 2) and contributes to safety:
npx claudepluginhub jeffreytse/grimoire --plugin grimoireDiagnoses brake system faults from symptoms like noise, pulsation, pulling, soft pedal, or warning lights to determine urgency and root cause before driving or seeking repair.
Performs prognostic assessment on vibration signals: trend analysis, degradation onset detection, and RUL estimation using predictive-maintenance-mcp server.