What 393.50(b) means in plain language
A 393.50(b) citation means an inspector found your steering mechanism to be defective, broken, or not functioning properly. This is a structural and operational defect—not a paperwork issue or a minor adjustment. Your steering system is what allows you to control the direction and stability of your truck, and any failure in that system is a safety-critical problem.
The steering mechanism includes the steering wheel, linkages, tie rods, steering gear box, and all connected components that translate your input at the wheel into directional movement. If the inspector documented movement, play, cracks, binding, or inability to turn the wheel without excessive resistance or unusual noise, you may receive this citation. The regulation focuses on actual function: can the steering respond to driver input safely and reliably?
This is not about alignment, tire wear, or cosmetic damage. It is about the mechanical integrity of the steering system itself.
What our enforcement data actually shows
Across our 13 million inspection records, 393.50(b) is cited very rarely. All-time, we have recorded 61 citations for this code. In the last 12 months, there have been 0 citations, and in the last 90 days, 0 citations as well. This makes 393.50(b) ranked #1569 out of 3,036 FMCSR codes by citation volume—far below the enforcement frequency of most other vehicle maintenance violations.
When 393.50(b) is cited, the out-of-service (OOS) rate is 3.3%: only 2 vehicles out of 61 were placed out of service. This is substantially lower than the all-FMCSR average OOS rate of 31.4%, suggesting that most 393.50(b) citations result in warnings or correctable violations rather than roadside vehicle impounds.
The rarity of this citation likely reflects two factors: first, steering defects that are severe enough for inspection notice are relatively uncommon in the active fleet due to routine maintenance; second, many steering issues are caught during pre-trip or scheduled maintenance before they become inspection findings.
Who gets cited most
Because the all-time citation count is only 61, these citations are distributed across many small carriers and independent operators. No state or carrier dominates the data. Our records show that carriers such as TEXAS MATERIALS GROUP INC and GREAT DANE LLC each have 1 citation on file. The top vehicle makes cited for 393.50(b) include Freightliner (FRHT, 5 citations) and Kenworth (KW, 4 citations), which reflects the overall composition of long-haul and vocational fleets rather than any particular vulnerability in those brands.
The low volume means that if you have received a 393.50(b) citation, you are part of a small group. This also means the citation carries weight: an inspector saw something they deemed unsafe enough to document.
How severe is this compared to similar codes
Steering defects fall in the Vehicle Maintenance category, alongside codes like 393.9(a) (Inoperable required lamps, 660,737 citations, 15.4% OOS rate) and 393.11 (Lighting devices/reflectors, 179,734 citations, 1.8% OOS rate). Both of those codes are cited far more frequently than 393.50(b).
A more directly comparable maintenance violation is 393.47E (Slack adjuster defective, 180,363 citations, 0.0% OOS rate), which addresses brake system defects. That code is cited thousands of times more often than steering defects, yet generates zero out-of-service orders in our data. By contrast, steering controls vehicle safety at the most fundamental level—direction and stability in motion—making it arguably more critical than a slack adjuster, which addresses braking performance.
The CSA severity weight for 393.50(b) is 8, reflecting its safety significance in the regulatory scoring system, even though citation volume is minimal.
How to avoid it
Steering defects are largely preventable through disciplined pre-trip inspection and prompt maintenance:
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Before each trip, turn the steering wheel fully left and right while parked. Feel for binding, grinding, or unusual resistance. The wheel should turn smoothly without clunking or play at the center position. Any hesitation, noise, or dead zones warrants immediate inspection by a mechanic.
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Check for visible damage or corrosion on steering linkages and tie rods during your walk-around. Look underneath the front end for bent, cracked, or loose components. Do not assume small bends are harmless; steering geometry is precise.
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Listen for steering-related noises during low-speed maneuvers—clunks, squeaks, or groaning when turning. These often indicate wear in tie rod ends, ball joints, or the steering gear itself. Document and report them immediately to your carrier or maintenance team.
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Verify that your carrier's maintenance schedule includes annual or semi-annual steering system inspections. Many fleets focus on brakes and tires and let steering slip. Steering systems do wear, especially in rough operating conditions or after high mileage.
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Never ignore play in the steering wheel. More than a quarter-inch of free movement at the rim before the wheels respond is a red flag. Report it before an inspector notices it at a roadside stop.
Because this violation is so rare, any citation likely signals a defect that went undetected or unreported for some time. Your best defense is aggressive pre-trip discipline and a maintenance culture in your fleet that treats steering with the same urgency as brakes.