What 393.75C means in plain language
This citation means an inspector measured the tread depth on one or more tires on your non-steer axles — your drive axles or trailer axles — and found it below the federal minimum of 2/32 of an inch. The steer axles have their own, stricter standard; 393.75C applies specifically to every other axle on the combination.
Tread depth is measured at the shallowest point in any major tread groove. If that measurement comes in under 2/32 inch on any non-steer tire, you're in violation — regardless of how the rest of the tires on that axle look. One bad tire on a drive axle can generate this citation.
The practical significance is straightforward: worn tread reduces traction, increases stopping distance on wet or slippery roads, and raises the risk of a blowout at highway speed. Federal rules treat 2/32 inch as the floor, not a target — by the time you're near that threshold, the tire has already done most of its useful work.
What our enforcement data actually shows
Across our database of 13 million+ inspections, 393.75C has generated 38,759 all-time citations, placing it at #83 out of 3,036 FMCSR codes by citation volume. That's a high-frequency violation — it's not an obscure rule that catches one fleet by surprise. Enforcement is clearly active and widespread.
In just the last 12 months, our inspection records show 23,963 citations for this code. The last 90 days alone account for 5,491 citations, which signals that enforcement has not cooled off.
The out-of-service picture is significantly better than most violations. Of 38,759 all-time citations, 1,664 resulted in an OOS order — a rate of 4.3%. For context, the all-FMCSR average OOS rate across all codes in our database is 31.4%. So while this code carries a CSA severity weight of 5 and will land in your safety record, inspectors place drivers out of service for it far less often than the typical FMCSR violation. That said, 1,664 OOS orders in the dataset proves it does happen — don't assume a citation automatically means you drive away.
Looking at the monthly trend, citation volume has run between roughly 1,870 and 2,391 per month from May 2025 through March 2026, with a peak of 2,391 in October 2025. February and March 2026 both exceeded 2,300 citations, suggesting enforcement attention on tire condition remains elevated heading into spring.
Who gets cited most
Our inspection records for the last 180 days show Texas leading all states with 10,476 citations and a 4.5% OOS rate. Iowa comes in second at 319 citations with a 0.0% OOS rate — inspectors in Iowa are writing the ticket but not parking trucks for it. North Carolina follows at 283 citations with a 6.0% OOS rate.
The OOS-rate spread across those top three states is material. Illinois, while lower in total volume at 170 citations, posts a 15.3% OOS rate — more than three times the Texas rate and well above the national average for this code. If your routes include Illinois, the data suggests inspectors there are applying a harder standard when worn tires are found.
On the carrier side, our data shows fleets such as VRP TRANSPORTES DE MEXICO S DE RL DE CV (USDOT 662058) with 214 all-time citations and RS TRANSFER SA DE CV (USDOT 1156825) with 194 citations appearing at the top of the all-time list. The concentration of citations among cross-border carriers in the top-ten list is a pattern worth noting for fleet safety managers building inspection protocols for Mexico-domiciled equipment.
How severe is this compared to similar codes
Within the Vehicle Maintenance category, 393.75C's enforcement footprint is modest by comparison. Peer code 393.9(a) — Inoperable Required Lamps has accumulated 660,737 citations with a 15.4% OOS rate — more than 17 times the all-time volume of 393.75C and a far higher OOS risk. 396.3(a)(1) — Inspection/Repair/Maintenance (general) shows 236,919 citations with a 45.3% OOS rate, meaning nearly half of those inspections end with the vehicle parked. 393.11 — Lighting Devices/Reflectors sits at 179,734 citations with a 1.8% OOS rate, similar in its low OOS profile but significantly higher in raw citation volume.
Compared to those peers, 393.75C is mid-tier in frequency and well below average in OOS risk. However, its CSA severity weight of 5 means each citation still accumulates points against your Unsafe Driving and Vehicle Maintenance BASIC scores, affecting carrier SMS percentile rankings even when no OOS order is issued.
How to avoid it
Our inspection records show 393.75C appearing alongside a consistent set of other violations in the same inspection. That co-occurrence pattern points directly to the pre-trip habits that break down before a citation happens.
- Check tread depth on every non-steer tire during pre-trip. Carry a tread depth gauge — they cost under $5. Measure the shallowest groove on each tire. If any reading is close to 2/32 inch, flag the tire for replacement before dispatch, not at a scale house.
- Inspect brake hardware at the same time. In the last 90 days, 393.45B2UV (brake tubing/hose condition) appeared in 730 shared inspections with 393.75C, and 393.47E (slack adjuster defective) appeared in 518. Worn tires and neglected brake components tend to surface together — if one is marginal, treat it as a signal to look harder at the other.
- Walk around your trailer axles, not just your drives. UTIL and WANC trailers appear among the top cited vehicle makes in our database — trailer tires wear unevenly and are easier to overlook during a rushed pre-trip.
- Check lighting while you're at the rear of the truck. 393.9 (inoperable required lamp) shows up in 1,668 shared inspections over the last 90 days — the single most common co-occurring code. If your trailer tires are due for attention, your rear lights are statistically likely to be a problem too.
- Don't skip the periodic inspection paperwork. 396.17C (no proof of periodic inspection) appeared in 534 shared inspections. A current, documented inspection gives you a baseline record of tire condition and supports your defense if a dispute arises at a weigh station.
- Pay extra attention if you run FRHT or KW equipment. Freightliner units account for 12,854 all-time citations under this code, and Kenworth units account for 5,359. If those are your tractors, your pre-trip tire check is not optional — it's where the data says citations come from.