FMCSR 393.75B: Steer Tire Tread Depth — Driver Q&A

Not automatically — but it happens more often than you'd expect for a non-mandatory OOS code. Across all-time inspection records, 393.75B carries a 16.0% OOS rate (474 out of 2,959 citations resulted in a vehicle being placed out of service). That figure is actually below the all-FMCSR average of 31.4%, so inspectors don't pull trucks as aggressively on this code as they do on many others. Still, roughly 1 in 6 citations ends with the truck parked. If the tread is borderline, don't assume you'll drive away — an inspector who measures below 4/32 inch on a steer axle tire has the discretion to act.

393.75B carries a CSA severity weight of 7. In the Vehicle Maintenance BASIC, that base score is then multiplied by a time-weight factor: violations from the most recent 6 months apply a 3× multiplier, violations from 6–12 months ago apply 2×, and violations older than 12 months apply 1×. So a fresh citation effectively counts as 21 weighted points before any inspection-level adjustments. The score attaches to both the driver's PSP record and the carrier's Safety Measurement System profile, meaning a single inspection can move numbers for both parties simultaneously.

Act on tires first, then audit everything else on that truck. Here's why: in our inspection records, 393.75B shows up alongside other violations constantly in the same inspection. In the last 90 days alone, it shared inspections with 393.9 (inoperable lamps, 118 times), 393.75C (tread on other axles, 65 times), 393.78 (windshield defects, 60 times), and 396.17C (no proof of periodic inspection, 48 times). Steps to take immediately:

1. Have a certified tire technician measure and document tread depth on all axles.
2. Walk every exterior lamp — 393.9 is the single most common co-citation.
3. Pull your last periodic inspection certificate and confirm it's on board.
4. Check windshield and glazing condition before the next run.
5. Keep all repair receipts; you'll need them if you challenge the citation.

It's mid-range in seriousness — nowhere near the worst, but not trivial. Our inspection database ranks 393.75B at #442 out of 3,036 FMCSR codes by citation volume, with 2,959 all-time citations. Its 16.0% OOS rate sits well below the 31.4% all-FMCSR average. For context, peer Vehicle Maintenance code 396.3(a)(1) — general inspection and maintenance — carries a 45.3% OOS rate across 236,919 citations. However, the steer axle location makes this violation safety-critical: inspectors know that a tire failure on the front axle affects steering control directly, which is why the 4/32-inch threshold for steers is stricter than for drives.

Yes, you can submit a DataQ request, and equipment-based findings like this one are contestable when supporting documentation exists. The FMCSA DataQs system (Request for Data Review, or RDR) lets drivers and carriers challenge inspection findings they believe are incorrect. For 393.75B, a successful challenge typically requires a dated repair invoice or a technician's measurement record showing tread depth was at or above 4/32 inch at the time of inspection. Because this is an equipment finding — not a documentation check — the burden is on you to produce physical evidence. Challenges to documentation-only codes like 396.17C tend to resolve faster; equipment disputes take longer and succeed less often without a strong paper trail.

Texas is by far the heaviest enforcement state for this code. In the last 180 days, our inspection records show TX with 719 citations and a 17.2% OOS rate on 393.75B stops — dwarfing every other state. Iowa is a distant second with 31 citations (6.5% OOS rate), followed by Illinois with 27 citations (7.4% OOS rate). North Carolina recorded 16 citations with a 0.0% OOS rate in that window, and New Mexico logged 8 citations also at 0.0%. If your routes run through Texas, particularly cross-border corridors, steer tire condition should be a pre-trip priority — the citation volume there is not close.

Fix it before the next dispatch — enforcement volume on this code is climbing. In the last 12 months our records show 1,796 citations, and the 90-day count stands at 380. Monthly volumes have been consistently in the 130–191 range from August 2025 through March 2026, with October 2025 and October peaks hitting 191 citations in a single month. The 16.0% all-time OOS rate means a meaningful share of drivers citing this code don't move the truck that day. Waiting is a gamble: steer tires below 4/32 inch are both a federal violation and a genuine blowout risk, and inspectors in high-volume states like Texas are actively measuring.

It follows both. Under FMCSA's CSA system, a 393.75B citation recorded during a roadside inspection attaches to the driver's Pre-employment Screening Program (PSP) record and simultaneously scores against the carrier's Vehicle Maintenance BASIC in the Safety Measurement System. Drivers carry their PSP history across employers, so a citation earned while working for one carrier is visible to any future employer who pulls a PSP report. Carriers accumulate the BASIC percentile that can trigger FMCSA intervention. With a severity weight of 7 and the potential OOS flag on 474 of 2,959 historical inspections, both the driver and the fleet have a real stake in preventing this citation.