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
Tire-related DVIR exceptions are tagged to the vehicle and tire position. Pattern detection — for example, the right steer always wearing faster — surfaces alignment or component issues.