Brake out-of-service violations: which defects park the truck
Brakes draw more roadside violations than almost anything else on a truck, but most of them never stop it. FMCSA's 2025 inspection data shows which brake defects end the trip, and which ones add up until they do.
Written by Rigo Diaz
Brake violations at U.S. roadside inspections, 2025
Brake out-of-service violations stop a vehicle where it stands. The most common is the 20% rule: when 20% or more of the service brakes on a vehicle or combination are defective, it is out of service. Damaged hoses, failed air loss tests, unhooked breakaway systems, and dead parking brakes park a truck on their own.
Every year CVSA reports that brake violations are the most-cited vehicle out-of-service violation at roadside inspections, and every year carriers hear it as a reason to worry about brakes in general. The more useful question is narrower: which brake findings actually stop the truck, and which ones only go on the report?
I spent more than six years in risk management before I founded Simplex, and I have led it for more than 25 years. An out-of-service order is the moment a maintenance gap becomes a missed load, a tow, and a mark on your safety record at the same time. FMCSA's own 2025 numbers show where those orders come from.
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Generated with AI text-to-speech from this article's key insights, in order, rather than reading it word for word. Chapter times come from a transcript of the audio. The article itself was written and reviewed by Rigo Diaz.
Key takeaways
The 20% rule parks the most trucks
In 2025 it produced 61,877 out-of-service violations, more than any other vehicle violation code but one: tires leaking or below half their maximum inflation.
One loose brake rarely stops you
Out-of-adjustment brakes were cited 133,062 times and never placed a vehicle out of service on their own. They count toward the 20%.
Some defects stop you alone
Hose damage through the reinforcement ply, a failed air loss test, an unhooked breakaway, a dead parking brake, or a dead steering-axle brake.
ABS lamps are cited, not parked
Of 152,320 ABS citations in 2025, 30 were out of service. Each still counts in your Vehicle Maintenance BASIC.
The order follows you for two years
The truck cannot move under its own power until repaired, you certify within 15 days, and the violations count in CSA for 24 months.
In this articleContents
Which brake out-of-service violations were most common in 2025?
The 20% defective brakes rule was the most common brake out-of-service violation in 2025, with 61,877 orders at U.S. roadside inspections. Only one vehicle violation code produced more: tires leaking or below half their maximum inflation pressure. Damaged hoses, unhooked breakaway systems, and dead parking brakes came next.
Brakes are everywhere in the data. Six of the 20 most-cited vehicle violations were brake codes, and by our grouping of FMCSA's brake codes, brakes accounted for 27% of all vehicle violations and 29% of vehicle out-of-service violations. But the brake codes cited most often are not the ones that stop trucks.
| Violation | Times cited | Out of service |
|---|---|---|
| Brake out of adjustment | 133,062 | 0 |
| 20% or more of service brakes defective | 62,109 | 61,877 |
| Air hose or tubing damaged or not secured | 60,135 | 1,030 |
| Trailer ABS malfunction lamp defective | 57,604 | 2 |
| Audible air leak at a proper connection | 53,952 | 175 |
| Automatic adjuster fails to compensate for wear | 50,203 | 7 |
| Hose damage through the outer reinforcement ply | 24,707 | 22,986 |
| Breakaway not attached to the towing vehicle | 21,201 | 21,052 |
| Parking brake inoperative or missing on the power unit | 10,482 | 10,340 |
| Fails air loss rate test | 7,450 | 7,272 |
The pattern holds in CVSA's own campaigns. At International Roadcheck 2026, brake systems made up 24.3% of vehicle out-of-service violations and the 20% rule another 14.9%, for 39.1% combined. Brake problems in California follow the same shape, as our California brake violations guide shows.
What percentage of defective brakes puts you out of service?
Twenty percent. CVSA's out-of-service criteria place a vehicle out of service when 20% or more of the brakes on the vehicle or combination have a condition that impairs braking enough for the brake to be considered defective. FMCSA records it under 49 CFR 396.3(a)(1).
On a five-axle tractor-trailer with 10 brakes, 2 defective brakes are enough. On a straight truck with fewer brakes, the margin is smaller still.
Why out-of-adjustment brakes add up instead
An out-of-adjustment brake is the most-cited brake violation in the country and the second most-cited vehicle violation of any kind. Yet none of the 133,062 citations in 2025 put a vehicle out of service by itself. Each one counts toward the 20% instead, so it is the second or third bad brake on the same combination that ends the trip.
The readjustment limits are set in 49 CFR 393.47(e) by chamber type and size: 2 inches for a standard type 30 clamp chamber, 2 1/2 inches for a long-stroke type 30. How far past the limit a brake must be to count as a whole defective brake is set in CVSA's out-of-service criteria handbook.
When the steering axle is different
A steering-axle brake that does not work is out of service on its own, whatever the count on the other axles. Of 1,902 citations for an inoperative steering-axle brake in 2025, 1,848 parked the vehicle.
Which brake defects put a truck out of service on their own?
Defects that affect the whole air system or the whole combination stop the truck by themselves, without any count. In 2025, these were almost always written as out of service:
- Hose damage through the outer reinforcement ply: 22,986 of 24,707 citations. On nylon tubing, a second color showing through is enough.
- Breakaway braking: a breakaway not attached to the towing vehicle (21,052 of 21,201) or missing or inoperable (14,746 of 14,863). Under 49 CFR 393.43(d), trailer brakes must apply automatically if the trailer breaks away and stay on for at least 15 minutes.
- Parking brake inoperative or missing on the power unit: 10,340 of 10,482.
- Audible air leak anywhere other than a proper connection: 9,664 of 11,196.
- Failed air loss rate test: 7,272 of 7,450.
- Low-air warning device missing or inoperative: 2,450 of 2,506.
Compare those with their milder cousins. A hose that is damaged or not secured, but not worn through the ply, was out of service in 1,030 of 60,135 citations. An audible leak at a proper connection was out of service in 175 of 53,952. The difference between a note on the report and an out-of-service order is how far the wear has gone.
Several of these are things a driver can catch before leaving the yard: a hooked-up breakaway, a working parking brake, a low-air warning that sounds. Our pre-trip inspection guide covers the walk-around.
How does a brake out-of-service order count against you?
It stops the truck first, then follows your safety record for two years. Under 49 CFR 396.9, no one may operate a vehicle marked out of service until the repairs are done, and it may be towed away only by a vehicle using a crane or hoist. Within 15 days, the carrier must certify on the inspection report that every violation was corrected.
How the CSA math works
In FMCSA's Safety Measurement System, the 20% code has a severity weight of zero and contributes only the 2 points for an out-of-service order. The brake violations underneath it carry their own weights, mostly 4 each. SMS counts each violation code once per inspection and caps one inspection at 30 points per BASIC.
So two out-of-adjustment brakes that trigger the 20% rule score 4 for the adjustment code plus 2 for the out-of-service order: 6 points. In the first six months that is multiplied by 3, then by 2, then by 1 until it drops off at 24 months.
The Vehicle Maintenance intervention threshold is 80% for most carriers, 75% for hazmat carriers, and 65% for passenger carriers. Our guide to how CSA scores affect truck insurance covers what underwriters see when they look at that record.
How do you keep brake defects from adding up to 20%?
Treat every brake finding as part of a count, not as a one-off. The 20% rule rewards fleets that fix the first bad brake before the second one shows up.
Step 1: Record stroke at every service
CVSA's pushrod stroke brochure suggests logging stroke at each wheel end every time it is measured. A brake creeping toward its limit shows up in the log weeks before it shows up on an inspection report. Our brake inspection checklist covers how to measure.
Step 2: Fix the adjuster, not just the stroke
Automatic adjusters have been required on air-braked vehicles built since October 1994. CVSA warns that simply repositioning an automatic slack adjuster does not repair it, and the brake will keep going out of adjustment until the cause is found.
Step 3: Make the stand-alone items a pre-trip habit
Breakaway hooked up, parking brake holding, low-air warning working, no hose worn through to its second layer. These are fast checks, and in 2025 they were behind tens of thousands of out-of-service orders.
Step 4: Close out and review every report
Certify repairs within the 15 days, keep the report, and look at brake findings by unit each month. A truck that keeps coming back with the same finding needs parts, not another adjustment. If a violation was recorded wrong, our guide on recovering from a DOT violation covers the DataQs process.
How Simplex helps you stay ahead of brake out-of-service orders
Brake orders start in the shop and end in your safety record. We help with both ends: the maintenance records and the monitoring.
Know the moment a truck is inspected
Our compliance programs include inspection and violation alerts, CSA monitoring and reporting, and DataQs support for violations that were recorded wrong.
Watch the Vehicle Maintenance BASIC
Our CSA program team tracks your BASICs and helps you fix the programs behind a rising Vehicle Maintenance score.
Maintenance you can prove
Our DOT safety compliance team sets up and maintains the programs FMCSA expects, including documented vehicle maintenance.
Frequently asked questions
What percentage of defective brakes puts a truck out of service?+
Is a brake out of adjustment an out-of-service violation?+
Is an ABS warning light an out-of-service violation?+
Can I drive to a shop after a brake out-of-service order?+
How long does a brake out-of-service violation stay in my CSA scores?+
Do brake violations count against the driver?+
Where this information comes from
The data and rules below come from FMCSA's inspection statistics and Safety Measurement System documents, CVSA, and federal regulations, checked on October 19, 2026.
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1
FMCSA A&I — Roadside Inspection Violations, Vehicle, CY 2025
Citations and out-of-service counts for every vehicle violation code at U.S. roadside inspections in 2025.
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2
FMCSA — SMS Methodology, version 3.21
How the 20% brake code is scored, time weights, the per-inspection rules, and Vehicle Maintenance thresholds.
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3
FMCSA — SMS Methodology Appendix A
Severity weights for each brake violation code, and which codes count in the driver measurement system.
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4
eCFR — 49 CFR 396.9
Out-of-service vehicles may not move until repaired; towing by crane or hoist; 15-day certification.
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5
eCFR — 49 CFR 393.43
Breakaway braking: trailer brakes must apply automatically on breakaway and stay applied for 15 minutes.
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6
CVSA — 2026 Brake Safety Day Results
CVSA's definition of the 20% defective brakes criterion and the other brake out-of-service categories.
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7
CVSA — FAQs: Brake Systems and Inspections
Brake hose and tubing conditions that are out of service, and automatic adjuster dates.
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8
CVSA — 2026 International Roadcheck Results
Brake systems and 20% defective brakes as shares of vehicle out-of-service violations in May 2026.
Written by
Rigo Diaz
Founder & CEO, Simplex Group
Founder and CEO of Simplex Group, with more than 25 years leading the company and helping trucking entrepreneurs navigate compliance, insurance, and the day-to-day demands of running a carrier. Before founding Simplex, he spent more than six years in risk management, experience that continues to shape how he approaches insurance, compliance, and carrier risk today.
Published · Updated
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