CVSA Out-of-Service Criteria for Brakes

What does CVSA look for during Brake Safety Week and International Roadcheck?

Published on
July 28, 2025 at 8:18:00 AM PDT July 28, 2025 at 8:18:00 AM PDTth, July 28, 2025 at 8:18:00 AM PDT

Each year, certified inspectors of the Commercial Vehicle Safety Alliance (CVSA) check thousands of commercial vehicles for safety and compliance, often with a heavy emphasis on brake systems. In fact, brake inspections take center stage during CVSA's National Brake Safety Week, a yearly event usually scheduled for the last full week of August. Additionally, CVSA holds a surprise "Brake Inspection Day" that typically takes place in April.

Beyond Brake Safety Week and other CVSA inspection events, such as International Roadcheck, brakes are always a significant focus area during any commercial vehicle inspection. More importantly, bad brakes are one of the easiest ways to get hit with an out-of-service (OOS) violation. Such violations are issued when critical vehicle parts fail to meet safety standards, posing an immediate hazard. OOS violations will result in your vehicle being removed from operation until all violations are repaired/corrected and the vehicle passes reinspection.

In this guide, we'll discuss the North American Standard Out-of-Service Criteria (OOSC) for brake systems, per CVSA's 2025 edition. While not all violations will result in an out-of-service designation, any safety violations found during inspections should be repaired prior to re-dispatch of the vehicle.

20% Defective Brakes OOS Violation

CVSA authorities inspect each service brake separately for several "defective" conditions. If at least 20% of your required or equipped brakes have a defective condition, an out-of-service violation will be issued until all defective brakes are repaired and reinspected.

The 20% rule applies to the total number of brakes required for your vehicle combination (including towed trailers or vehicles). If the vehicle combination is equipped with more brakes than required, the total number of brakes equipped will be used for calculations.

You can calculate 20% by multiplying your total brakes by 0.2. For example, if your vehicle combination requires and is equipped with 10 brakes, it will be declared out-of-service if 2 brakes have an applicable defective condition. If 20% of your total brakes equals a fractional number, CVSA rounds up to the next whole number for the 20% rule. Example: If you have 12 total brakes and 20% equals 2.4, you round up to 3.

Defective Brake OOS Criteria

A defective brake is any individual brake that meets one or more of the conditions below. Each defective brake (even if it has multiple defective conditions) counts as "1" defective brake toward the 20% total.

General Defective Conditions (All Brake Types)▼

No braking action when applying the brake (i.e. the brake mechanism is inoperative and doesn't work).
Missing or broken parts and components for the specific brake type (includes, but is not limited to, brake shoes/pads, calipers, pushrods, linings, adjusters, springs, bolts, yoke, pins, and retainers).
Air chamber has audible air leak.
Brake is 1/4" (6.4mm) or more beyond the adjustment limit. (Also considered half-defective if 1/8" (3.2mm) beyond the adjustment limit. See Adjustment Limits section below for more info.)
Drum or rotor has visible evidence of metal-to-metal contact on friction surface.
Friction surface of drum/rotor and brake friction material are contaminated by oil, grease, or brake fluid.*

Drum Air Brakes Defective Conditions▼

Loose air chamber, spider, or camshaft support bracket.
Lining has cracks or voids exceeding 1/16" (1.6mm) that are visible from the lining’s edge.
Lining is missing segment material that exposes a fastening device (bolt/rivet) and is visible from the lining’s edge.
Lining is loose with 1/16" or more movement.
Lining has a crack exceeding 1.5" (38.1mm) in length.
Lining thickness is less than 1/4" (6.4mm) or worn beyond wear indicator.

Air Disc Brakes Defective Conditions▼

Loose or missing brake chamber or caliper mounting bolt.
Entire friction surface of rotor has severe rusting on either side (light rust is okay).
Brake pad thickness is less than 1/16" (1.6mm) or worn beyond wear indicator.

Hydraulic or Electric Brakes Defective Conditions▼

Loose or missing brake caliper mounting bolt.
Caliper movement within anchor plate exceeds 1/8" (3.2mm) in the direction of the wheel rotation.
Entire friction surface of rotor has severe rusting on either side (light rust is okay).
Lining or pad thickness is 1/16" or less (drum or disc brakes).
All electric brakes of the towed vehicle do not have an electrical connection.*

Front Steering Axle Brakes Defective Conditions▼

All defective conditions for each brake type listed above, plus any of the defective conditions below.
Missing steering axle brake(s) where required on tractors or trailers.
Mismatched air chamber sizes.
Mismatched brake adjuster length.
For brake shoes with a continuous strip of lining, the lining thickness is less than 3/16" (4.8mm).
For brake shoes with two lining segments, the lining thickness is less than 1/4" (6.4mm) or worn beyond the wear indicator.

Brake Adjustment Limits – Full and Half Defective Conditions for 20% Rule

CVSA inspectors measure brake adjustment limits in 1/8" increments. If the brake is 1/4" or more beyond its adjustment limit (which varies by brake chamber type), then it is considered defective and counts as "1" defective brake toward your total for the 20% rule.

However, it is also a violation to have a brake 1/8" or more beyond the adjustment limit. In this case – and assuming there are no other defects found for the brake – CVSA will declare the brake as "half" defective and count it as "0.5" against your total. If your final total of defective brakes is a fractional number, CVSA rounds down this time to the nearest whole number (e.g. 1.5 defective brakes would be rounded down to 1 defective brake for the 20% rule).

Note: If a vehicle combination (such as a truck and trailer) is in violation of the 20% rule, the out-of-service status is only applied to vehicles from the combination that have defective brake conditions. Any vehicle from the combo that did not have any defective brakes may still proceed on the roadway, provided it has no other OOS conditions.

Front Steering Axle Brake Standalone OOS Violation

In addition to being used for 20% rule calculations, any front steering axle brakes that have a defective condition (as listed in the previous section) will immediately warrant a standalone OOS violation as well. In other words, one wrong thing with a steering axle brake will place your vehicle out of service. Even if you otherwise pass the 20% rule, you can still get an OOS violation for a defective steering axle brake alone.

Brake Components Standalone OOS Criteria

CVSA inspectors will check several components of the brake assembly for standalone OOS violations as well. Each of the critical conditions below will result in a separate OOS violation.

Spring Brake Chamber▼

If your spring brake chamber has cracks or non-manufactured holes in the parking brake housing section, you will receive an OOS violation.

Trailer Breakaway and Emergency Braking▼

Commercial trailers and dollies must be equipped with a breakaway braking system.

If the system is missing, not working, or mounted incorrectly, it is an OOS violation.
The breakaway braking system must be directly connected to the towing vehicle. If not, such as being bolted to the hitch, it is an OOS violation.
Additionally, for trailers equipped with spring brakes, at least 75% of the brakes must be operational. If more than 25% of the trailer's spring brakes are defective/not working, it is an OOS violation.

Parking Brake▼

If the brakes for the vehicle or vehicle combination are not applied when activating parking brake controls, it is an OOS violation.

Brake Smoke or Fire▼

If smoke or fire is emitting from the wheel end due to a brake malfunction, the vehicle likely has an OOS violation. One exception is overheating caused by severe brake use, which is not a violation. However, smoke and fire can also be caused by an issue with the wheel. If evidence of smoke or fire is found, CVSA inspectors will also examine the wheel hub and bearings to determine the root cause of the violation. They will then record the OOS citation for the applicable part (i.e. brake system or wheel hub).

Brake Drums and Rotors▼

As we mentioned in the first section of this guide, the 20% Defective Brakes Rule includes potential OOS criteria for brake drum and rotor problems. However, evidence of any of the issues below will result in a standalone OOS violation:

Brake drum has an external crack or visible cracks that open when the brake is applied.
Brake drum or rotor has a missing segment or piece that may break off.
Rotor has a crack measuring longer than 75% of the friction surface that fully passes through (1) to the center vent, (2) a solid rotor, or (3) a structural support connection for friction surfaces.
Rotor is worn to or through the center vents.

Air Brake System OOS Criteria

Air brakes are powered and engaged via air pressure. If the brake system doesn't maintain pressure levels and apply consistent pressure when needed, the brakes may fail. Thus, brake hoses and other air pressure components have several OOS criteria.

Air Brake Hose/Tubing OOS Violations

Air brake hoses and tubing are often a focus area for CVSA special inspection events like Brake Safety Week. Any of the air brake hose and tubing conditions listed below can result in an out-of-service violation.

Damage to the reinforcement ply layer▼

The reinforcement ply is the fabric or steel braid/spiral layer found beneath the hose's outer cover material. It's okay for the reinforcement ply to be visible (i.e. damage to outer cover only), but if the ply is frayed, severed, or cut, it is an OOS violation. Additionally, if the inner tube of a thermoplastic nylon tube is exposed (distinguishable from the outer cover by color differences), it is an OOS violation.

Bulging or swelling▼

If there is bulging or swelling in the hose/tubing when the system supplies air, it is an OOS violation.

Audible air leaks▼

An audible air leak occurring in the hose or tubing is an OOS violation. However, CVSA excludes air leaks occurring between hose/tube connection points (like gladhands, swivel or non-swivel joined metal fittings, or push-to-connect fittings). Leaks occurring on the hose side of a connection point are still an OOS violation.

Improper connections▼

If the hose or tube is connected improperly, such as via splicing or clamping, it is an OOS violation.

Heat damage or broken▼

Any hoses or tubes that are broken or have visible heat damage are an OOS violation.

Labeled for a different application type▼

If the hose/tube used on the vehicle is not designed for air brake system applications, it is an OOS violation.

Service gladhand not connected▼

If the required brakes on trailer or towed vehicle are not working due to a disconnected gladhand, it is an OOS violation.

Air Pressure OOS Violations

CVSA also sets several safety standards to ensure the vehicle's air pressure is maintained at safe operating levels.

Pressure Component	Out-of-Service Criteria
Air Compressor	Air compressor has loose mounting bolts; or Has a broken, cracked, or loose pulley; or Has broken/cracked mounting brackets, braces, or adapters.
Air Loss Rate	If there is an air leak, the primary/secondary reservoir doesn't maintain pressure when any of the following occur: Air governor is cut-in. Reservoir pressure is 80 to 90 psi. Engine is idle. Service brakes are fully applied or released.
Air Pressure Gauge	The primary or secondary air pressure gauge is defective or doesn’t work.
Air Reservoir (Tank)	The air reservoir/tank is separated from or not fully connected to attachment points and moves 1" or more in any direction.
Low Air Pressure Warning Device	Low air pressure warning device is missing or does not work; or There is no continuous operation when the primary/secondary reservoir is 55 psi or less or half of the governor cut-out pressure (whichever is less). Note: The OOS violation does not apply if the audible or visual warning device is working.
Tractor Protection System	The tractor protection system is missing components, such as the tractor protection valve or trailer supply valve. The system is not properly operating, evidenced by: The trailer supply valve not closing before pressure drops under 20 psi in both primary and secondary systems; or Air escaping from any gladhand when the tractor protection valve is shut and brakes are applied.

Hydraulic Brake System OOS Criteria

For bad hydraulic brake systems, there are eleven conditions – mostly related to hoses, pressure, and fluid – that can result in a stand-alone OOS violation for any brake-axle type.

Loose Master Cylinder Assembly▼

If there are missing or loose mounting bolts that cause the master cylinder assembly to move/shift out of position, it is an OOS violation.

Low Fluid▼

If fluid levels are less than 1/4 full or below the minimum levels marked in the master cylinder reservoir, it is an OOS violation.

Bad Hoses and Lines▼

Lines, hoses, or connections that are designed/labeled for a different application are an OOS violation. It is also a violation if they are crimped, blocked/restricted, broken, or damaged through the outer reinforcement ply layer.

Hose Pressure Buildup▼

If the brake hose is bulging/swelling or has visible seepage when operating and pressure is applied, it is an OOS violation.

Hose/Tube Improperly Joined▼

If the hose or tube is improperly connected to the brake line, such as via splicing or clamping, it is an OOS violation.

Fluid Leaks▼

Any visible hydraulic fluid leaks that occur during full application of the brake system are an OOS violation.

No Pedal Reserve▼

If there is no pedal travel reserve when the engine is running and you fully apply the brakes, it is an OOS violation.

Bad Brake Power Assist Unit▼

If the brake power assist unit is not working, it is an OOS violation.

Bad Hydraulic Power Brake Unit▼

If the hydraulic power brake unit assist unit is not working, it is an OOS violation.

Brake Failure Warning System Issues▼

If the brake failure warning system is missing, disconnected, not working correctly, or activated when the engine is running (with or without brake application), it is an OOS violation.

Bad Hydraulic Brake Backup System▼

If the hydraulic brake backup system is not working, it is an OOS violation.

Vacuum Brakes System OOS Criteria

If a commercial vehicle is equipped with vacuum brakes, meeting one of the two conditions below can result in an out-of-service violation.

Insufficient Vacuum Reserve▼

After the engine is shut off, if there is inadequate vacuum reserve to allow for one full brake application, it is an OOS violation.

Bad Hoses or Lines▼

If the vacuum hoses or lines are restricted, crimped, cracked, broken, or damaged through the outer cover to the cord ply (including chafed), it is an OOS violation. It is also a violation if the hose collapses when the vacuum is applied.

Performance-Based Brake Test OOS Criteria

If the commercial vehicle undergoes a Performance-Based Brake Test (PBBT) during its inspection, it must have a minimum total vehicle braking efficiency of 43.5% to avoid receiving a violation according to the North American Standard OOSC. However, U.S. and Canada authorities have additional brake efficiency requirements for some vehicle types.

United States

The 43.5% requirement primarily applies to property-carrying, single-unit vehicles with a GVWR over 10,000 lbs. and vehicle combinations (vehicles towing property). The FMCSA requires a minimum braking efficiency of 52.8% for passenger-carrying vehicles with a seating capacity greater than 10 and single-unit vehicles with a GVWR of 10,000 lbs. or less. Vehicles with a passenger-car chassis and capacity of 10 or less must have a minimum braking efficiency of 65.2%.

Canada

In addition to a minimum braking efficiency of 43.5% for the total vehicle, each wheel must have a minimum braking efficiency of 40%.

Note: PBBT use varies by jurisdiction, which can also impact how you meet the requirements to remove the OOS status. If an approved PBBT is available, inspectors can retest the vehicle to determine if the vehicle now meets the braking efficiency requirements after repair. If a PBBT is not available, a CVSA agent must inspect all brake fault areas identified on the PBBT inspection report for safety compliance.

Blog / Industry News