What 393.47A-RW means in plain language
Your vehicle was cited because a brake chamber on your commercial motor vehicle has visible damage—either a crack or a break in its housing. A brake chamber is a critical component of your air brake system that converts compressed air into mechanical force to stop your rig. The housing is the metal shell that contains the internal mechanisms.
When that shell develops a crack or breaks, two things happen: first, compressed air can leak out, degrading your braking power over time; second, moisture and road contamination can enter the chamber, corroding internal parts and reducing system reliability. Either way, it's a safety issue that Federal Motor Carrier Safety Regulations require you to fix before operating the vehicle.
This is a defect citation, not an immediate out-of-service order in most cases—but it still lands on your record and signals to inspectors and your carrier that your brake system needs attention.
What our enforcement data actually shows
Across our 13 million inspection records, 393.47A-RW is rarely cited. We've recorded only 1 citation all-time for this specific code, with that same 1 citation occurring in the last 12 months. In the last 90 days, there have been 0 citations for this violation.
When this code is cited, the enforcement outcome is severe: our data shows a 100.0% out-of-service rate. To put that in context, the all-FMCSR average out-of-service rate is 31.4%, meaning this code is cited in circumstances that almost always result in a vehicle being placed out of service. However, the extremely low citation volume—ranking 393.47A-RW at #2796 of 3,036 FMCSR codes—means most drivers will never encounter this citation. If you have, you're in a very small group.
Who gets cited most
Our enforcement database does not show meaningful geographic or carrier distribution for this code due to its low citation volume. We have one recorded citation attributed to ACC TRANSPORTATION LLC (USDOT 4074089). This single data point is not sufficient to establish a pattern or trend across states or fleets.
How severe is this compared to similar codes
Brake system and vehicle maintenance citations vary widely in enforcement frequency and out-of-service impact. For comparison:
393.9(a) — Inoperable required lamps has seen 660,737 citations all-time with a 15.4% out-of-service rate. That's a much more common citation, but far fewer result in the vehicle being placed out of service.
396.3(a)(1) — Inspection/repair/maintenance - general records 236,919 citations with a 45.3% out-of-service rate—nearly halfway to a vehicle removal, and representing a broader maintenance category.
393.47E — Slack adjuster defective is closely related to brake function and has 180,363 citations but only a 0.0% out-of-service rate, meaning defective slack adjusters are typically cited as violations without vehicle removal.
The 100.0% out-of-service rate on 393.47A-RW, despite its rarity, indicates that inspectors view a cracked or broken brake chamber as serious enough to immediately take the vehicle off the road.
How to avoid it
A cracked or broken brake chamber is a result of impact damage, age-related fatigue, or corrosion that has gone undetected. Here's what you can do:
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Inspect brake chambers every pre-trip. Walk around the entire brake assembly on each side of the vehicle. Look for visible cracks, gaps, or dents in the cylindrical metal housings. If you see any, report it immediately before moving the truck.
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Check for air leaks. During your pre-trip inspection, listen near the brake chambers for hissing sounds, which indicate compressed air escaping. If you hear it, the housing is likely compromised.
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Avoid road debris and curb contact. Brake chambers hang below the frame and are vulnerable to impact from potholes, curbs, and debris. Drive defensively and avoid tight spaces where your brake hardware might clip obstacles.
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Keep your brake system serviced on schedule. Your carrier's preventive maintenance program should include periodic brake chamber inspection and replacement before they crack. Don't skip scheduled service intervals.
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Report any brake system issues to your fleet immediately. If you feel soft brakes, longer stopping distances, or hear unusual sounds from the brake system, get the truck inspected before you're cited or lose braking power on the road.
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Document your pre-trip inspection. Record the condition of brake chambers and other brake components on your vehicle inspection report (DVIR). This creates a record that defects are being caught early and protects you if a defect develops between inspections.