FMCSR 393.75(b): Steer Tire Tread Depth — Driver Q&A

It can, but it doesn't happen the majority of the time. Across 10,962 all-time citations for 393.75(b) in our inspection records, 2,298 vehicles were placed out of service — a 21.0% OOS rate. That means roughly 1 in 5 drivers cited for this violation was parked on the spot. The other 79% received the citation without an immediate OOS order. That said, 21.0% is a real risk you cannot ignore, especially since steer tires directly control your ability to steer the vehicle. An inspector who spots severely worn tread has every reason to pull that truck.

393.75(b) carries a severity weight of 7 in the CSA SMS scoring system. That base score is then multiplied based on how recently the violation occurred: inspections within the last 6 months carry the full multiplier weight, and those in the 6–12 month window carry a reduced one. Because 393.75(b) falls in the Vehicle Maintenance BASIC (BASIC 5), the points accumulate against the carrier's Vehicle Maintenance BASIC percentile. A severity weight of 7 is toward the upper end of the scale, making this a meaningful hit to any carrier's safety score — especially if multiple steer-tire citations stack across a fleet.

Act on the tire immediately before moving the vehicle if an OOS order was issued. Here's the priority sequence:

1. If placed OOS: Do not move the truck until a qualified mechanic measures and confirms tread depth meets the 4/32" minimum on the steer axle. Get a repair receipt with the date and technician's name.
2. If not placed OOS: Schedule tire inspection or replacement before your next dispatch — the violation is on record regardless.
3. Document everything: Keep the inspection report, repair invoice, and any tread-depth gauge readings.
4. Notify your fleet safety manager: This citation will appear on your carrier's FMCSA record and affects their Vehicle Maintenance BASIC score.
5. Check your other tires: A cited steer tire often signals a broader maintenance gap worth reviewing fleet-wide.

It's less likely to trigger an OOS order than the average FMCSR violation, but it's still significant. The all-FMCSR average OOS rate across our database is 31.4%. At 21.0%, 393.75(b) comes in below that average. Compare it to a peer code like 396.3(a)(1) — general inspection and maintenance — which carries a 45.3% OOS rate across 236,919 citations. However, steer-tire tread depth is uniquely safety-critical because it directly affects vehicle control. Inspectors treat it seriously even when they don't issue an OOS order, and the 7-point CSA severity weight reflects that. With 10,962 all-time citations, this code ranks #218 out of 3,036 FMCSR codes by citation volume — firmly in the top 10%.

Yes, you can submit a DataQs request — but success depends on what you can document. Because 393.75(b) is an equipment violation rather than a paperwork deficiency, a successful challenge typically requires objective evidence that contradicts the inspector's finding: a tread-depth gauge reading taken at or shortly after the inspection showing the tire met the 4/32" minimum, or documentation that the inspector measured the wrong tire or location. Unlike citation types where a missing document can be produced after the fact, equipment findings are harder to overturn without contemporaneous evidence. File your DataQs RDR (Request for Data Review) through the FMCSA DataQs portal within the relevant correction window and attach all supporting repair and measurement records.

Our inspection records don't break down 393.75(b) citations by state in the available data, but the top vehicle makes cited give a clear picture of where enforcement is concentrated by fleet type. Freightliner variants (FRHT and FREIGHTLIN combined) account for 1,371 of the 10,962 all-time citations, followed by Ford at 688 and Kenworth (KW) at 352. These are common long-haul and regional fleet platforms operating nationwide. For state-level citation data on this specific code, checking the FMCSA's SAFER system or filtering inspection records by state in a compliance tool will give you the most current breakdown.

Treat it as urgent regardless of whether an OOS order was issued. Our inspection records show a 21.0% OOS rate on this violation — meaning inspectors actively pull trucks for it. The citation is already on your FMCSA record, so the compliance clock is running. Notably, our database shows 0 citations for 393.75(b) in the last 90 days, which suggests the code may be getting absorbed into related citation entries — but that doesn't reduce your legal or safety obligation. A steer tire below 4/32" affects vehicle handling and braking. If you're re-inspected before the repair is made, you face a repeat violation and potentially a higher OOS risk.

It follows both, but in different ways. In the FMCSA's CSA system, vehicle maintenance violations like 393.75(b) are attributed to the carrier's Vehicle Maintenance BASIC score, not a personal driver score. However, the inspection event is tied to both the driver's license and the carrier's USDOT number. Carriers with the most all-time citations for this code in our records include CNC LOGISTICS S DE RL DE CV with 38 citations, RS TRANSFER SA DE CV with 31, and FEDERAL EXPRESS CORPORATION with 26 — showing that repeated citations concentrate on specific operators over time. Drivers should be aware that a pattern of vehicle-condition violations on their inspection history can affect their employability even if there is no personal CSA score.