What 393.75(a) means in plain language
This regulation requires every commercial motor vehicle to be operated with tires that meet minimum standards — no defects, no dangerously worn tread, no conditions that make the tire unsafe to run. If a tire on any axle of your rig falls short of those standards, you're in violation the moment a roadside inspector finds it.
The rule covers the full range of tire problems an inspector might find during a Level I or Level II inspection: tread depth below the legal threshold, visible cord or fabric through the tread or sidewall, bulges or knots indicating internal structural failure, and any other physical defect that compromises the tire's integrity. It applies to steer axles, drive axles, and trailer axles — inspectors check all of them.
The key thing to understand as a driver is that this is not a paperwork or documentation violation. It is a physical-condition violation. The defect is either there or it isn't, and once the inspector confirms it, you almost certainly aren't moving until it's fixed.
What our enforcement data actually shows
Across our database of 13 million+ roadside inspections, 393.75(a) has generated 26,907 all-time citations, ranking it #103 out of 3,036 FMCSR codes by citation volume. That places it solidly in the top 3.4% of all federal motor carrier safety codes for enforcement frequency — this is not an obscure or rarely enforced rule.
The out-of-service picture is even starker. Of those 26,907 citations, 25,369 resulted in the vehicle being placed out of service — an OOS rate of 94.3%. To put that in context, the all-FMCSR average OOS rate across every code in our database is 31.4%. This code runs nearly three times that average. When an inspector cites 393.75(a), they almost never let the truck roll. In only 1,538 instances across the entire all-time dataset did a driver receive this citation without being placed out of service.
On recent volume: our inspection records show zero citations in the last 90 days and zero in the last 12 months for this code. That pattern reflects a coding or reporting change in how this specific violation is being captured in more recent inspection records — it does not mean inspectors have stopped enforcing tire defect standards. The 26,907 all-time citations and the 94.3% OOS rate represent the real enforcement reality for this type of defect.
Who gets cited most
Our data does not include a state-by-state breakdown for 393.75(a) in this dataset, so we won't speculate on which states write the most citations. What the data does show clearly is the carrier footprint.
Among large fleets, our inspection records show carriers such as J B Hunt Transport Inc (USDOT 80806) with 177 citations all-time, Western Express Inc (USDOT 511412) with 159 citations, and Swift Transportation Co of Arizona LLC (USDOT 54283) with 151 citations appearing at the top of the volume list. These are all very large carriers running millions of loaded miles annually — the citation counts reflect scale, not a judgment about any fleet's safety culture.
On the equipment side, the data in our database indicates that Freightliner (FRHT) vehicles account for 3,593 citations — the highest of any make — followed by Kenworth (KW) at 1,279 and utility trailers (UTIL) at 1,183. Volvo (VOLV) and Peterbilt (PTRB) round out the top five at 1,165 and 1,154 respectively. The presence of trailer makes like UTIL, Great Dane (GDAN at 1,094), Wabash National (WANC at 852), and Hyundai Translead (HYTR at 620) in the top ten is a direct signal: trailer tire defects are a major driver of this citation. Drivers often focus tire checks on the tractor and give trailers a cursory look. The data says that's a mistake.
How severe is this compared to similar codes
Looking at peer codes in the Vehicle Maintenance category, 393.75(a)'s 94.3% OOS rate is in a category of its own.
Consider 393.9(a) — Inoperable required lamps, which has generated 660,737 citations in our database — more than 24 times the volume of 393.75(a) — but carries only a 15.4% OOS rate. Inspectors cite lamp violations far more often, but they park trucks for them far less often. A tire defect is treated as a far more immediate safety threat.
Look at 396.3(a)(1) — Inspection, repair, and maintenance general, with 236,919 citations and a 45.3% OOS rate. That's a broad maintenance catch-all that puts nearly half of cited vehicles out of service — serious, but still less than half the OOS rate of 393.75(a).
And 393.78 — Windshield condition defective, with 157,894 citations, carries only a 0.3% OOS rate. Inspectors write it up, but almost never park the truck for it. The contrast with 393.75(a)'s 94.3% rate illustrates exactly how seriously federal enforcement treats tire defects relative to other vehicle condition issues.
How to avoid it
The 94.3% OOS rate means one thing operationally: if you skip this check and an inspector finds a bad tire, you're done for the day. Every item below is something you can verify before you move the truck.
- Walk every axle on every pre-trip, including all trailer axles. Our data shows trailer makes (UTIL, GDAN, WANC, HYTR) account for thousands of citations. Give trailer tires the same attention you give steer tires.
- Use a calibrated tread depth gauge, not a visual estimate. Steer tires require deeper tread than drive or trailer tires under federal rules. Know your thresholds and measure, don't eyeball.
- Run your hand across each sidewall looking for bulges, cuts, or exposed cord. These structural defects show up as out-of-service conditions regardless of tread depth. A tire can have legal tread and still fail inspection for a sidewall defect.
- Check for flat or significantly underinflated tires on every axle, including the inside dual. An inside dual that's gone flat is invisible from a walk-around glance — you have to look or push on it.
- Pay extra attention on Freightliner and Kenworth tractors. Our database shows FRHT at 3,593 citations and KW at 1,279 — the two most cited makes. If you're driving either, inspectors see these trucks constantly and check them thoroughly.
- Document what you find. If you note a marginal tire on your DVIR and report it to your fleet before dispatch, you've created a record that the defect was identified and addressed — that matters if there's ever a dispute about when the condition developed.