What 393.209B-STWLOOS means in plain language
When an inspector cites you for 393.209B-STWLOOS, they've found a problem with your truck's hub or bearing. This includes any defect, looseness, or visible sign of failure in these critical components. Hubs and bearings are what allow your wheels to spin freely while supporting the full weight of your truck and cargo. If one fails while you're moving, the wheel can seize or lock up, and you lose control.
Inspectors check for this during a Level 1 roadside inspection by spinning the wheels by hand, looking for grinding sounds or resistance, and visually examining the components for wear, corrosion, or damage. They may also feel for play or wiggle in the wheel when it's jacked up.
This is not a warning. Finding a defective or loose hub or bearing is serious enough that your truck will be removed from service immediately.
What our enforcement data actually shows
Across our 13 million inspection records, 393.209B-STWLOOS is cited relatively infrequently—186 all-time citations—but every single one results in an out-of-service order. Our data shows a 100.0% OOS rate for this code, compared to the all-FMCSR average OOS rate of 31.4%. That means every driver cited for this violation has had their truck detained.
In the last 12 months, we recorded 102 citations for hub or bearing defects. Over the last 90 days, the pace accelerated slightly to 18 citations. Monthly citation counts have ranged from 1 in April 2025 to 12 in September 2025, with recent months hovering between 5 and 11 citations per month.
Nationally, 393.209B-STWLOOS ranks #1235 out of 3,036 FMCSR codes by citation volume, placing it outside the most frequently cited violations but firmly in the upper-middle range of enforcement activity.
Who gets cited most
Over the last 180 days, Arizona leads all states with 10 citations, followed by South Carolina with 7, and Colorado with 3. All three states show a 100.0% OOS rate—meaning every citation in those states resulted in the truck being taken out of service.
Our all-time data shows certain carriers appearing more frequently in our records. PREMIUM CARRIER'S LOGISTICA SA DE CV, JESUS PEDRO PEREZ CARRILLO, STANLEY TRUCKING LLC, CONCRETE WORLD LLC, and FEDERAL EXPRESS CORPORATION each appear with 2 citations in our database. This does not suggest any carrier is unsafe; it reflects the volume of inspections and the random nature of roadside enforcement.
How severe is this compared to similar codes
Within the Vehicle Maintenance category, hub and bearing defects are treated far more seriously than many other violations. For context:
- 393.9(a) — Inoperable required lamps has 660,737 citations with a 15.4% OOS rate. Lights are easier to fix and don't pose an immediate safety hazard to vehicle control.
- 393.47E — Slack adjuster defective has 180,363 citations with a 0.0% OOS rate. A defective slack adjuster is a serious maintenance issue but doesn't always warrant roadside removal.
- 396.3(a)(1) — Inspection/repair/maintenance (general) has 236,919 citations with a 45.3% OOS rate, still lower than the 100.0% rate you see here.
The 100.0% OOS rate places hub and bearing defects among the most serious mechanical violations discovered at roadside. Inspectors have no discretion—if a hub or bearing is failing, the truck cannot move.
How to avoid it
Hub and bearing failures don't occur overnight. The inspection data reveals patterns that can help you stay ahead of this violation:
- Check for wheel looseness during your pre-trip. Grasp the tire near the 3 and 9 o'clock positions and try to rock it. If you feel play, the bearing is loose. Do not drive. This is the single most actionable check you can perform.
- Listen for grinding or humming sounds while the truck is moving, especially at highway speeds. Defective bearings often produce a distinct grinding noise that grows louder as you accelerate. If you hear it, have the axle inspected immediately.
- Inspect brake and suspension components together. Our data shows 393.209D (wheel fasteners loose/missing) co-occurs in 7 shared inspections, 393.45B2 (brake tubing issues) in 5, and 393.207A (suspension defective) in 3. Loose fasteners, brake problems, and suspension wear all contribute to bearing failure. During pre-trip, check all wheel fasteners for tightness and inspect brake lines for damage.
- Pay special attention if you drive a Freightliner, Kenworth, or Peterbilt. Our records show 37 Freightliner citations, 20 Kenworth, and 17 Peterbilt for this code. These popular trucks are well-maintained when serviced correctly, but they're also high-volume on the road. Follow your OEM maintenance schedule precisely.
- Have your bearings serviced or repacked on schedule. Bearings require regular inspection, cleaning, and regreasing. If your fleet or maintenance shop skips this, failure is nearly inevitable. The cost of preventive service is a fraction of the cost of roadside repair, towing, and downtime.
- Check tire pressure and condition. Four co-occurring codes involve tire defects. Over- or under-inflated tires increase load on bearings and accelerate wear. Inspect tires weekly and maintain the pressure specified on your door jamb.
Your goal is simple: catch bearing wear before an inspector does. A loose hub detected at pre-trip can be reported to maintenance and fixed at a shop. A defective bearing detected at roadside means your truck is done for the day, your cargo is delayed, and your CSA record takes a 7-point severity hit.