Section 393.75 covers tire condition, tread depth, load rating, and related criteria. Roadside inspectors check tires on every Level I, Level II, and Level V inspection.
Common sub-codes
- 393.75(a): flat tire or audible air leak — OOS.
- 393.75(b): tread depth less than 4/32 inch on a steering axle — OOS.
- 393.75(c): tread depth less than 2/32 inch on other axles — OOS.
- 393.75(h): load rating exceeded.
Severity weights
Steer-axle tire defects carry severity weight 8 in the Vehicle Maintenance BASIC. Other-axle tire defects carry weight 3.
How to prevent it
- Pre-trip walk-around with a tread depth gauge — eyeballing it is unreliable below 6/32.
- Air pressure check at every fueling. Underinflation kills tires faster than anything else.
- Replace before the wear bars meet the road, not after. The OOS criteria are minimums, not targets.
- Match tires by size, ply, and tread design across an axle.
How Roadworthy HQ helps
A tire citation shows up in Roadworthy HQ as part of the inspection it came from, not as a record of its own: the app does not store individual violation codes. Log the roadside inspection on the vehicle's Inspections tab: date, state, level, driver, the number of violations, and whether it was out-of-service. For an out-of-service inspection the 15-day §396.9(d)(3) repair-certification countdown stays on that tab until you enter the certification date. The rule's 15 days cover every violation on the report, not only out-of-service ones, so for a non-OOS inspection that date is yours to track. The repair itself goes in the vehicle's maintenance log: date, type, what was done, who did it, and cost. DVIRs are logged per vehicle with the defect described in your own words, and a defect marked safety-affecting that is logged without a repair certification sends a critical alert.