Inflation
- Schedule and perform inflation checks based on specified maintenance intervals.
- Verify that replacement tires meet or exceed original equipment specifications.
- Determine tire serviceability based on remaining tread depth measurements.
- Tire pressure gauge — Measure internal air pressure, as inflation cannot be judged by visual inspection alone.
- Tread depth gauge — Measure remaining tread to ensure it is not at or below the replacement limit.
- Air compressor with regulator — Adjust tire pressure to the recommended setting while tires are in a cold state.
Check pressure at least monthly and before every long trip, cold, before driving. Never bleed down hot tires.
You cannot judge inflation by looking — use a gauge.
Replace tires at 2/32" tread remaining.
Replacement tires must have a size, load rating and speed rating equal to or greater than the original.
How It Works
The Cold Inflation Rule
Tire pressure must be checked when tires are cold, specifically before driving. Pressure should be checked at least monthly and before every long trip. Technicians must never bleed down tires that have become hot from operation.
Visual Inspection Limitations
It is impossible to accurately judge the inflation status of a tire simply by looking at it. A calibrated gauge is the only reliable method for verifying that the tire is maintaining its required pressure.
Criteria for Tire Replacement
Tires must be removed from service when they reach 2/32" of remaining tread. When installing new tires, the size, load rating, and speed rating must be equal to or greater than the original equipment specifications.
Diagnostic Chart
| Symptom | Check | Spec / Expected | Likely cause & fix |
|---|---|---|---|
| Tire appears properly inflated upon visual inspection. | Perform a physical pressure check using a tire gauge. | Per the applicable manual | Inflation cannot be judged by looking; the tire may be underinflated despite its appearance. Basis: Hankook Special Trailer (ST) Tire Warranty & User Guide (2024) |
| Tire pressure is higher than the cold spec after a long drive. | Verify if the tire is hot and do not adjust pressure. | Never bleed down hot tires. | Tires naturally increase in pressure when hot; bleeding them will result in underinflation once they cool. Basis: Hankook Special Trailer (ST) Tire Warranty & User Guide (2024) |
| Tread shows significant wear across the footprint. | Measure the remaining tread depth at the shallowest point. | 2/32" | The tire has reached its wear limit and must be replaced. Basis: Hankook Special Trailer (ST) Tire Warranty & User Guide (2024) |
| Replacement tire options are being evaluated. | Compare the size, load rating, and speed rating of the new tire to the original. | Equal to or greater than the original. | Installing a tire with lower ratings than the original equipment is a safety violation. Basis: Hankook Special Trailer (ST) Tire Warranty & User Guide (2024) |
At the Bay: Diagnose the Case
CASE 1 / 4
Tire appears properly inflated upon visual inspection.
- Test
- Compare
- Correct
Select the next check
Basis: Hankook Special Trailer (ST) Tire Warranty & User Guide (2024). A likely cause is a hypothesis; confirm it with the applicable service procedure before repair.
Common Bay Mistakes
- ✕ Attempting to estimate tire pressure visually without a gauge.
- ✕ Bleeding air out of a hot tire to reach a 'cold' pressure spec.
- ✕ Checking pressure only once a year or ignoring it before long trips.
- ✕ Installing a replacement tire with a lower speed or load rating than the original.
- ✕ Leaving a tire in service with only 2/32" tread remaining.
Quick Check
Practice only — not scored.
Source: Hankook Special Trailer (ST) Tire Warranty & User Guide (2024)