What 393.75A1 means in plain language
FMCSR 393.75A1 targets a specific and visible tire defect: when the internal structural layers of a tire — the plies or belts that give the tire its strength — are no longer protected by the outer rubber and are open to the elements and road contact. Think of it as the skeleton of the tire being exposed. A tire in that condition has lost a critical layer of protection against a blowout.
This isn't a minor scuff or surface wear issue. The regulation is concerned with cases where the underlying reinforcement material — whether cord fabric or steel belting — is visibly accessible. That can happen from road hazard damage, severe sidewall cuts, or tread that has worn down past any reasonable safe limit.
The practical implication for a driver is straightforward: if an inspector can look at your tire and see material beneath the outer rubber, you are citable under this section. It is a condition that should be visible during any thorough pre-trip inspection, which is exactly why citations for this violation are so common.
What our enforcement data actually shows
Across 13 million inspections in our database, 393.75A1 has generated 11,383 all-time citations, placing it at #208 out of 3,036 FMCSR codes by citation volume. That ranking puts it firmly in the top 7% of all cited codes nationally — this is not an obscure or rarely enforced rule.
Enforcement is accelerating. Our inspection records show 7,267 citations in the last 12 months alone, and 1,560 citations in just the last 90 days. Looking at the monthly trend, citations climbed from 596 in May 2025 to a peak of 720 in August 2025, then settled into a consistent range of 595–683 citations per month through early 2026. That volume indicates active, sustained enforcement, not seasonal spikes.
The out-of-service picture is more nuanced. Officially, 393.75A1 is not OOS-eligible under the standard North American OOS criteria. Yet our data shows that 2,731 of 11,383 all-time inspections still resulted in an OOS placement — a 24.0% OOS rate. That is actually below the all-FMCSR average OOS rate of 31.4%, but it is far from zero. Inspectors have discretion, and when this violation appears alongside other defects — which happens frequently, as shown below — the combination can push an otherwise borderline inspection over the OOS threshold. Of the 11,383 all-time citations, 8,652 did not result in an OOS placement, which is the more common outcome, but nearly one in four still did.
Who gets cited most
The state-level data in our database reveals dramatic enforcement geography. Over the last 180 days, Texas dominates with 2,926 citations — far above every other state. At a 16.8% OOS rate in Texas, citations there are frequent but less likely to result in a vehicle being parked compared to other states.
North Carolina comes in second with 122 citations, but with a 64.8% OOS rate — nearly four times Texas's rate. If you're rolling through a North Carolina inspection station with exposed ply showing, the odds of being placed out of service are substantially higher than the national average.
New Mexico records 82 citations over the same period, and every single one — 100.0% — resulted in an OOS placement. That is not a rounding artifact; our records show 82 citations and 82 OOS placements in New Mexico. Drivers crossing into New Mexico should treat any tire condition concern as a serious OOS risk, not a fix-it-later item.
The variation between states — 16.8% in Texas versus 100.0% in New Mexico — is a difference of more than 83 percentage points. Inspector interpretation and local enforcement posture clearly matter here.
Among carriers, our data shows fleets such as TRANSPORTE INTERNACIONAL LOPEZ OCHOA SA DE C V (USDOT 1041907) with 26 all-time citations and HLH LOGISTICS INC (USDOT 3294766) with 23 citations leading the citation counts in our records. High citation counts at the carrier level typically reflect high inspection exposure — fleets running heavy mileage through active enforcement corridors.
How severe is this compared to similar codes
Putting 393.75A1 in context with peer codes in the Vehicle Maintenance category shows where it sits on the severity spectrum.
393.9(a) — Inoperable required lamps has 660,737 all-time citations in our database, dwarfing 393.75A1's 11,383. However, its OOS rate is only 15.4%, well below the 24.0% rate we see for exposed tire ply. Lamps get cited constantly but rarely park a truck; exposed tire ply parks one nearly a quarter of the time.
396.3(a)(1) — Inspection, repair, and maintenance (general) carries 236,919 citations and a 45.3% OOS rate. That higher OOS rate reflects how broadly it captures systemic maintenance failures. Compared to this, 393.75A1's 24.0% rate is lower, but the tire condition is more specific and directly tied to a catastrophic failure mode — a tire blowout at highway speed.
396.17C — No proof of periodic inspection shows 212,081 citations with a 0.0% OOS rate — it's a paperwork violation that rarely stops a truck. Exposed tire ply is not a paperwork issue; it is a physical condition that inspectors can see and act on immediately, which explains why its OOS rate is materially higher.
How to avoid it
The co-occurring violation data in our database makes clear that 393.75A1 rarely shows up alone. In the last 90 days, it appeared alongside 393.75C (insufficient tread depth on other axles) in 303 shared inspections, meaning an inspector who finds exposed ply on one tire is almost certainly going to check every other tire on the vehicle. A thorough pre-trip tire walk-around is not optional.
Here are the concrete actions that address the pattern our data reveals:
- Inspect every tire on every axle before departure. Run your hand along the sidewalls and look at the tread surface on all tires, not just the drives. Exposed ply is visible if you look for it — it shows as cord fabric or metallic belt material breaking through the rubber surface.
- Check for sidewall damage, not just tread depth. Road hazard cuts and impact breaks can expose belt material on the sidewall, not just the tread face. Our data shows FRHT (Freightliner) vehicles account for 3,977 all-time citations under this code, and KW (Kenworth) for 1,632 — these are high-mileage platforms where tire wear accumulates fast.
- Inspect lamps at the same time. With 556 shared inspections involving 393.9 (inoperable required lamp) in just the last 90 days, an inspector who writes you for tire ply is likely to check your lights immediately. Don't give them a second violation.
- Review brake adjusters during your pre-trip. 393.47E (slack adjuster defective) appeared in 181 shared inspections in the last 90 days alongside this code. If your maintenance program is missing tire issues, it is likely missing brake adjustment issues too.
- Don't leave the yard with a marginal spare or a known tire concern. New Mexico's 100.0% OOS rate is a signal that inspectors in certain corridors are treating this defect as an automatic stop. A tire that might pass a quick glance will not pass a thorough inspection in high-enforcement states.
- Check your fuel system and fire extinguisher on the same walk. Our records show 396.5B (fuel system leak) co-occurred in 231 inspections and 393.95A (missing or defective fire extinguisher) in 180 inspections alongside this code in the last 90 days. If your tire maintenance has slipped, other safety-critical items may have slipped with it.