Hours of Service Rules for Students

Last updated: April 2026

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Quick Answer

Modern air brake systems include service, parking, and emergency brakes, using compressed air for operation. A combination vehicle air brake system cannot leak more than 3 psi per minute with the engine off and the brakes released.
Drain air tanks daily to prevent water and oil buildup, a key maintenance step for air brake systems.
A 10-speed transmission is like two 5-speeds combined, with a shift pattern resembling an "M".
Shift a 10-speed transmission at 1500 RPM for optimal performance.

Learning to operate commercial vehicles involves mastering complex systems like air brakes and multi-speed transmissions. Air brakes are a reliable and safe way to stop large, heavy vehicles, but they require proper maintenance and use. Modern air brake systems are made up of three distinct parts: service brakes, parking brakes, and emergency brakes. A critical maintenance task involves draining air tanks daily to prevent the buildup of water and oil, which can impact system performance. When it comes to shifting, a 10-speed transmission, while seemingly complex, can be understood as mastering two separate five-speed patterns back-to-back. Drivers should aim to shift at 1500 RPM for efficient and smooth operation. For instance, a combination vehicle air brake system cannot leak more than 3 psi per minute with the engine off and the brakes released, highlighting the importance of a well-maintained system for safety and compliance.

What are the main components of an air brake system?

Modern air brake systems are designed with three primary components that work together to ensure a vehicle can stop safely and reliably. These include the service brakes, parking brakes, and emergency brakes. Each system serves a distinct purpose, relying on compressed air to function effectively in large, heavy vehicles.

The service brakes are what you use for normal braking while driving. When you press the brake pedal, it controls the air pressure applied to operate these brakes. This pedal acts as the main control in the system, dictating how much force is exerted on the slack adjusters through rods and connectors. The air pressure then activates the brake chambers, which apply the brakes. Without the proper functioning of the service brake system, a driver would lose the ability to slow down or stop the vehicle under normal conditions.

The parking brakes are used to hold the vehicle in place when it's stopped or unattended. These brakes are typically controlled by a diamond-shaped, yellow, push-pull control knob inside the cab. Pulling this knob out sets the parking brakes, while pushing it in releases them. During normal operations, both the parking and emergency brakes are usually held back by spring pressure. This spring pressure is crucial because it ensures that if air pressure is lost, the brakes will still engage automatically.

The emergency brakes are designed to stop the vehicle if there is a failure in the service brake system. In such an event, the emergency brake system is the one drivers rely on to bring the vehicle to a halt. Like the parking brakes, the emergency brakes also utilize spring pressure to function. If your vehicle has dual parking control valves, you can use pressure from a separate tank to release the emergency brakes to move a short distance. This feature also allows the vehicle to stay parked without using up the service air pressure, which is important for maintaining the primary air system.

An air compressor governor is another vital component, controlling when the compressor pumps air into the storage tanks. This mechanism ensures that the air pressure within the system remains within the optimal range, preventing both excessively low and dangerously high pressures. The air compressor itself builds up the air pressure needed for the brake system to operate. If this component fails, the entire air brake system would eventually become inoperable due to a lack of compressed air.

Lastly, some vehicles are equipped with an alcohol evaporator. This device is specifically designed to reduce the risk of ice forming in the air brake valves during cold weather. The alcohol helps to keep any moisture in the air from freezing, which could otherwise cause the brake valves to malfunction. If a vehicle has an alcohol evaporator, it needs to be checked and filled every day during winter weather. This preventative measure is crucial for maintaining brake system reliability in freezing conditions, ensuring that the compressed air lines and valves remain clear and functional.

Brake Pedal Function

The brake pedal serves as the primary interface for the driver to control the air pressure that activates the brakes. It is not just a footrest during normal driving but a critical component that transmits the driver's intent to the air brake system. The force applied to the pedal directly correlates to the amount of air pressure sent to the brake chambers, initiating the braking action.

Air Compressor Governor

This component is essential for regulating the air pressure within the air brake system. The governor controls when the air compressor pumps air into the storage tanks. It ensures that the system maintains a consistent and safe operating pressure, preventing the compressor from running continuously or allowing pressure to drop too low, which could compromise braking capability.

Alcohol Evaporator

In colder climates, moisture in the air lines can freeze, leading to brake system failures. The alcohol evaporator addresses this by injecting alcohol vapor into the air system. This helps to prevent ice formation in the air brake valves, ensuring that the system remains functional even in sub-zero temperatures. Drivers must ensure this system is properly maintained, especially during winter months, to mitigate the risk of brake malfunctions.

How do you inspect and maintain air brakes?

Proper inspection and maintenance of air brakes are critical for safety and compliance, as these systems are complex and vital for stopping large commercial vehicles. Regular checks and specific procedures help ensure that the air brake system operates correctly and reliably. One of the most fundamental maintenance tasks for an air brake system is draining the air tanks daily to prevent water and oil from building up. This simple step is vital because moisture and contaminants can corrode internal components and interfere with brake operation.

Inspecting slack adjusters is another key part of air brake maintenance. Slack adjusters are components of your air brake system used to adjust the brakes, found between the push rod and S-Cam on drum brakes. To check the free play in manual slack adjusters, you should park the vehicle on level ground, chock the wheels to prevent any movement, and then release the parking brakes. After these steps, you can use gloves and pull hard on each slack adjuster you can reach to check for excessive movement. Properly adjusted slack adjusters ensure that the brakes engage effectively and evenly. If slack adjusters are out of adjustment, it can lead to brake failure or fade, where the brakes lose their effectiveness due to overheating.

Air leaks are a serious concern in air brake systems. A combination vehicle air brake system cannot leak more than 3 psi per minute with the engine off and the brakes released. This strict standard emphasizes the importance of a sealed system for reliable brake performance. Leaks can deplete air pressure, leading to spring brakes engaging automatically, or even a complete loss of braking capability. Regular checks for air leaks, including listening for hissing sounds and observing the air pressure gauge, are essential.

Before leaving any vehicle unattended, especially one with an air brake system, it is crucial to follow specific safety protocols. You must put on the parking brakes and chock the wheels. This ensures the vehicle remains stationary and prevents accidental rolling, which could lead to severe accidents. Removing the keys is also a good practice to prevent unauthorized operation. These steps are not optional; they are fundamental safety measures that every commercial driver must adhere to.

Brake fade or failure can be caused by several factors, including excessive use of the service brakes, not relying enough on engine braking, and brakes being out of adjustment. On long, steep downgrades, brakes work as a supplement to the braking effect of your engine, not as the main braking mechanism. Over-relying on service brakes in these situations can cause them to overheat and lose effectiveness. This is why it's important to use engine braking to help slow the vehicle and reduce wear on the service brakes.

Maintaining your air tanks daily is not just a suggestion; it's a requirement to prevent issues. Water and oil can accumulate in the air storage tanks over time, leading to potential malfunctions and corrosion. Draining these tanks at the end of each working day helps to remove these contaminants, ensuring the longevity and proper functioning of the air brake system. This simple, routine task contributes significantly to the overall safety and reliability of the vehicle's braking capabilities.

Daily Air Tank Drainage

To prevent the buildup of water and oil, which can compromise the integrity and function of the air brake system, daily drainage of air tanks is mandatory. This process ensures that the compressed air remains clean and dry, protecting valves and other components from corrosion and freezing in cold weather. Failing to drain the tanks can lead to significant maintenance issues and potential brake failure.

Slack Adjuster Inspection

Properly adjusted slack adjusters are vital for effective braking. The process involves parking the vehicle on level ground, chocking the wheels, and then releasing the parking brakes. Drivers then manually pull on each slack adjuster to check for excessive free play. This inspection ensures that the brakes are within the correct adjustment range, allowing for optimal braking force and preventing premature wear or failure.

Air Leak Check

Maintaining air pressure is paramount for an air brake system. A combination vehicle air brake system is designed to be highly efficient, with a strict limit on air leakage: no more than 3 psi per minute with the engine off and the brakes released. Drivers must regularly check for leaks, as even small ones can lead to a gradual loss of air pressure, which can trigger the automatic engagement of spring brakes or reduce overall braking power. This strict standard is outlined in the Air Brakes CDL Practice Test materials.

Unattended Vehicle Procedures

Safety protocols for leaving a vehicle unattended are non-negotiable. Always engage the parking brakes and chock the wheels to prevent unintended movement. These steps ensure that the vehicle remains securely in place, minimizing the risk of accidents. Removing the keys adds an extra layer of security, preventing unauthorized use. These procedures are fundamental to responsible commercial vehicle operation.

What are spring brakes and how do they work?

Spring brakes are an essential safety feature in commercial vehicles, designed to provide braking power automatically, especially in emergency situations or when air pressure is lost. These brakes are made up of powerful springs that are held back by air pressure while the vehicle is driving. This means that as long as there is enough air pressure in the system, the springs are compressed and the brakes are released, allowing the vehicle to move freely.

However, if the air pressure in the system drops too low, these powerful springs are designed to engage automatically. This mechanism ensures that the truck or tractor will come to a halt even if there's a major air leak or the engine shuts off, preventing a runaway vehicle. This automatic deployment is a critical safety net for drivers of large commercial vehicles. The full effect of spring brakes is not achieved until the air pressure (PSI) drops to a certain range, often between 20 to 30 PSI. This specific pressure range is where the springs have enough force to fully apply the brakes, providing a reliable stop.

To test if your vehicle's spring brakes come on automatically, there's a specific procedure to follow. For tractor-trailer vehicles, the best way is to continue stepping on and off the brake pedal until the parking brake valve pops out. This action simulates a loss of air pressure, causing the spring brakes to deploy. Alternatively, you can continue to step on and off the brake pedal until the manufacturer's low PSI specification has been met for the spring brakes to deploy. This test confirms that the automatic engagement system is functioning correctly, which is vital for pre-trip inspections and overall vehicle safety.

Spring brakes are used for both parking and emergency situations. When you set the parking brake using the control knob in the cab, you are essentially releasing the air pressure that holds back the springs, allowing them to apply the brakes. In an emergency, such as a complete failure of the service brake system or a severe air leak, the spring brakes will engage automatically as the air pressure drops. This provides a fail-safe mechanism to bring the vehicle to a stop.

It's important to understand that spring brakes are distinct from the service brakes. While service brakes use air pressure to push brake shoes against drums or pads against rotors, spring brakes use the mechanical force of compressed springs. The air pressure in the system works against these springs to keep them compressed and the brakes released. When air pressure is removed or drops, the springs expand, applying the brakes. This design makes them incredibly reliable for parking and emergency stops, as they don't rely on continuous air pressure to hold the vehicle.

Knowing how spring brakes work and how to test them is a fundamental part of CDL training. This knowledge ensures that drivers can confidently operate their vehicles, understanding the safety systems in place and how to verify their functionality. The automatic nature of spring brake engagement provides a crucial layer of protection, making them one of the most important safety features on commercial trucks and buses.

Automatic Engagement

Spring brakes are engineered to engage automatically when the air pressure in the system falls below a predetermined threshold, often between 20 to 30 PSI. This critical safety feature ensures that the vehicle will come to a stop even if there is a catastrophic loss of air pressure, preventing runaway situations. The system relies on powerful springs that are held back by air pressure during normal operation.

Testing Procedures

Testing the automatic engagement of spring brakes is a vital part of pre-trip inspections. For tractor-trailer vehicles, this involves repeatedly pressing and releasing the brake pedal until the parking brake valve pops out, indicating that the spring brakes have deployed. Alternatively, drivers can monitor the air pressure gauge and continue braking until the manufacturer's specified low PSI for spring brake deployment is reached. This test confirms the reliability of the emergency braking system.

PSI Threshold

The effectiveness of spring brakes is directly tied to the air pressure in the system. They do not achieve their full braking force until the PSI drops into a specific range, commonly between 20 to 30 PSI. This threshold is crucial for drivers to understand, as it dictates when the emergency braking system will fully activate. Awareness of this range is key to anticipating and managing emergency braking scenarios.

When should you use specific braking techniques?

Understanding when and how to use specific braking techniques is crucial for safe and effective operation of commercial vehicles, especially given the complexities of air brake systems. Different situations call for different approaches to braking, from routine stops to emergency maneuvers and long descents. These techniques help manage brake wear, prevent overheating, and maintain control of the vehicle.

One critical piece of advice for driving on long downgrades is to never fan the brakes on and off. The reason for this is simple: the short time off the brakes does not allow for sufficient cooling. Instead, this technique can cause the brake linings to get excessively hot, leading to brake fade or even complete failure. When brakes overheat, they lose their ability to effectively slow the vehicle, creating a dangerous situation. It is much safer to use a steady, firm application of the brakes, combined with engine braking, to control speed on declines.

Engine retarders play a significant role in managing vehicle speed and preserving the service brakes. The purpose of engine retarders is to help slow the vehicle while driving and reduce brake wear. These devices, which can include exhaust brakes or compression release brakes, use the engine's compression to create resistance, thereby slowing the vehicle without relying solely on the friction brakes. Using engine braking as a primary method for slowing down, especially on downgrades, helps keep the service brakes cool and ready for when they are truly needed, such as for coming to a complete stop or in emergency situations. On a long, steep downgrade, brakes function as a supplement to the braking effect of your engine, not as the main braking mechanism.

In emergency braking situations, where you need to stop quickly, the stab braking technique is often recommended. To use the stab braking technique, you brake hard with the pedal until the wheels lock, then get off the brakes until the wheels begin to roll again. This method helps prevent skidding and allows the driver to maintain some steering control while bringing the vehicle to a rapid stop. It's a technique that requires practice to execute effectively, as the goal is to maximize braking force without losing control due to locked wheels.

Vehicles equipped with dual parking control valves offer additional flexibility in managing brake pressure. If your truck or bus has dual parking control valves, you can use pressure from a separate tank to release the emergency brakes to move a short distance. This can be useful for minor repositioning without fully building up the main air system. Additionally, these valves allow you to stay parked without using up service air pressure, which helps preserve the main air supply for driving operations. This system provides a convenient way to manage parking and emergency brake functions independently, offering more control and efficiency.

Understanding the nuances of these braking techniques is vital for any CDL student. It's not just about knowing how to press the pedal, but when and why to apply different methods to ensure safety and prolong the life of the vehicle's braking components. Proper use of engine braking, avoiding fanning the brakes, and mastering emergency techniques are all part of becoming a proficient and safe commercial driver. This knowledge is reinforced through specialized training, such as the Air Brakes Endorsement Course, which covers the intricacies of air brake operation and maintenance.

Braking on Downgrades

When descending long downgrades, it is crucial not to fan the brakes. Rapidly pressing and releasing the brake pedal does not allow the brake linings to cool, leading to dangerous overheating and potential brake fade. Instead, a consistent and controlled application of the service brakes, combined with effective engine braking, is the safest approach to maintain speed and prevent brake system failure.

Utilizing Engine Retarders

Engine retarders are designed to assist in slowing the vehicle and reducing wear on the primary service brakes. By creating resistance within the engine, these systems help manage speed, especially on long descents. Integrating engine braking into your driving technique prolongs the life of your service brakes and ensures they remain effective for critical stopping needs.

Emergency Braking: Stab Technique

In an emergency, the stab braking technique can be employed to achieve a rapid stop while minimizing skidding. This involves braking hard until the wheels lock, then quickly releasing the pedal until the wheels begin to roll again, and repeating the process. This method helps to regain traction and steering control during intense braking situations, which is essential for avoiding collisions.

Dual Parking Control Valves

For vehicles equipped with dual parking control valves, drivers gain enhanced control over their braking system. These valves allow for the use of separate air pressure to release emergency brakes for short movements or to maintain parking without depleting the main service air pressure. This flexibility is beneficial for precise maneuvering and efficient management of the air brake system.

How do you shift a 10-speed transmission?

Learning to shift a 10-speed transmission might seem daunting at first, but it becomes much simpler when you understand its underlying structure. The secret is realizing you're not learning ten unique gears. Instead, think of it as mastering two separate five-speed patterns back-to-back. This perspective, as highlighted by the Patriot CDL Blog, makes the process much less intimidating. A 10-speed is essentially two 5-speeds, one on top of the other, which means you're learning familiar patterns with an added dimension.

The shift pattern for a 10-speed transmission can be visualized as an "M" shape. This pattern helps drivers navigate through the gears systematically. Mastering this pattern is fundamental to smooth and efficient shifting. The transmission uses a "splitter" mechanism, which is a small lever or button on the shifter, to access the two different sets of gears. The splitter communicates with the transmission when the shifter is in NEUTRAL, allowing you to select between the low and high ranges of gears.

For the lower gears, you use the "Splitter Down" position. This range typically covers 1st through 5th gears, as well as Low Reverse. When the splitter is down, you operate within the first five-speed pattern. After engaging the clutch and moving the shifter into the desired gear, the splitter remains in the down position until you are ready to move into the higher range. This initial set of gears provides the necessary torque for starting from a stop and accelerating at lower speeds.

Once you've progressed through the lower gears and are ready for higher speeds, you move the splitter to the "Splitter Up" position. This activates the second five-speed pattern, giving you access to 6th through 10th gears, along with High Reverse. The transition from the low range to the high range often occurs after you've reached fifth gear, and then you typically split up to engage sixth. The key is to understand that the splitter is used to select which set of five gears you are currently operating within.

Timing is everything when it comes to shifting a 10-speed transmission. The general guideline is to shift at 1500 RPM. This RPM range is usually optimal for commercial truck engines, providing enough power for a smooth gear change without lugging the engine or over-revving. Consistent shifting at the correct RPM helps maintain momentum and reduces wear and tear on the transmission and engine. Developing a feel for the engine's sound and the tachometer is crucial for hitting this target consistently.

The actual physical act of shifting involves a precise coordination between the clutch and the shifter. When shifting, you move the shifter and push the clutch in at the same time. Crucially, you only need to depress the clutch pedal about 2-3 inches. This "short throw" clutch technique is different from what many car drivers are used to and takes practice. The goal is to quickly disengage and re-engage the clutch to allow the gears to mesh smoothly. Over-depressing the clutch is unnecessary and can slow down the shifting process.

Another important aspect of learning to shift is understanding the "hard walls and soft walls" of the shift pattern. The "walls" refer to the physical gates within the shifter mechanism that guide you to the correct gear slots. The hard walls require a firmer push or pull, while soft walls allow for easier movement. Learning to feel these distinctions helps prevent mis-shifts and ensures that the shifter moves into the intended gear path. This tactile understanding comes with practice and familiarity with the transmission. The process of learning to shift a 10-speed transmission isn't as intimidating as it looks. The secret is realizing you're not learning ten unique gears. Instead, think of it as mastering two separate five-speed patterns back-to-back, a perspective emphasized in the How to Shift 10 Speed Transmission: A CDL Student’s Practical Guide.

Understanding the "M" Pattern

The 10-speed transmission follows an "M" shaped shift pattern. This visual guide helps drivers mentally map out the gear positions, making the process of finding the correct gear more intuitive. Mastering this pattern is the first step towards smooth and confident shifting, as it provides a consistent framework for gear selection.

Splitter Functionality

The splitter is a crucial component that effectively doubles the number of available gears. When the splitter is in the "Down" position, it accesses gears 1-5 and Low Reverse. When moved "Up," it enables gears 6-10 and High Reverse. The splitter communicates with the transmission when the shifter is in neutral, allowing for the selection of the appropriate gear range. This mechanism is key to utilizing all ten speeds efficiently. This functionality is clearly outlined in the 10-speed Shifting TIPSHEET.

Optimal Shifting RPM

For optimal performance and longevity of the transmission, drivers should aim to shift at 1500 RPM. This specific engine speed provides the ideal balance of power and engine braking, allowing for smooth gear changes without straining the engine. Consistent practice to hit this RPM target is essential for developing proficient shifting skills and reducing wear on drivetrain components.

Clutch and Shifter Coordination

Effective shifting requires precise coordination between the clutch pedal and the shifter. The key is to move the shifter and push the clutch in simultaneously, using only 2-3 inches of clutch travel. This minimal clutch depression allows for quicker shifts and reduces clutch wear. Mastering this synchronized movement is fundamental to achieving seamless gear transitions in a 10-speed transmission.

What happens if your ABS fails?

The Anti-lock Braking System (ABS) is a critical safety feature in modern commercial vehicles, designed to prevent the wheels from locking up during hard braking. This system helps drivers maintain steering control and reduce stopping distances in emergency situations. However, like any complex electronic system, ABS can sometimes fail. It's important for CDL students to understand the implications of an ABS failure and how it affects the vehicle's braking capabilities.

If your ABS fails, it does not mean that you will lose all brake function. This is a common misconception that can cause unnecessary panic. Instead, if your ABS fails, you will still have normal brake function. The vehicle's traditional brake system, which relies on hydraulic or air pressure to activate the brakes, will continue to operate as usual. The primary difference will be the absence of the anti-lock feature, meaning the wheels could lock up during aggressive braking, similar to a vehicle without ABS.

When an ABS failure occurs, a warning light typically illuminates on the dashboard, alerting the driver to the issue. This indicator signals that while the basic braking system is still operational, the enhanced safety features of ABS are not. The immediate action required is simply to get the ABS repaired soon. Driving with a faulty ABS is not ideal, as it compromises a significant safety feature, but it does not render the vehicle undrivable or immediately unsafe in terms of basic braking capability.

It's crucial to understand that an ABS failure does not cause problems with other mechanical systems or pose a huge fire risk. The ABS operates independently of many other critical vehicle systems. Its malfunction is confined to its specific function of preventing wheel lock-up. The truck will not slow to a halt and force you to pull over due to an ABS failure itself, unless there are other, unrelated brake system issues. The truck will continue to operate with normal, albeit non-ABS-assisted, braking.

The purpose of ABS is to allow the wheels to continue rotating, even under heavy braking, preventing a skid and allowing the driver to steer around obstacles. Without ABS, if you brake too hard, especially on slippery surfaces, the wheels can lock, causing the vehicle to skid and making it impossible to steer. Therefore, while you still have normal brake function, you lose this crucial anti-skid capability. Drivers must adjust their braking technique accordingly, being mindful of potential wheel lock-up and the need to modulate brake pressure manually, similar to how one would brake in a vehicle without ABS.

In summary, an ABS failure is a serious issue that requires prompt attention, but it does not equate to a complete loss of braking. Drivers will retain normal brake function, but they must be aware that the anti-lock capabilities are no longer active. Getting the ABS repaired quickly is important for restoring the full safety features of the commercial vehicle. This knowledge helps CDL students understand the nuances of their vehicle's safety systems and react appropriately to potential malfunctions.

Continued Normal Brake Function

Despite an ABS failure, the vehicle's fundamental braking system remains functional. This means that drivers will still be able to apply the brakes and slow down or stop the vehicle. The primary change is the absence of the anti-lock feature, which prevents wheels from locking during hard braking. Drivers must be prepared to manually modulate brake pressure to avoid skidding.

Repair Urgency

While an ABS failure does not immediately incapacitate the vehicle, it is a significant safety concern that warrants prompt repair. The illuminated ABS warning light indicates that a crucial safety system is not active. Getting the ABS repaired soon is essential to restore the vehicle's full safety capabilities and ensure compliance with vehicle standards.

No Impact on Other Systems

An ABS malfunction is generally isolated to the anti-lock feature itself. It does not typically cause a cascade of problems with other mechanical systems, nor does it create a fire risk. The vehicle will not automatically come to a halt or become uncontrollable solely due to an ABS failure. The issue is confined to the specific function of preventing wheel lock-up during braking.

Frequently Asked Questions

What are the three systems found on modern air brake systems?

Modern air brake systems are equipped with three distinct and crucial systems to ensure safe vehicle operation. These include the service brakes, which are used for normal stopping; the parking brakes, which hold the vehicle stationary when parked; and the emergency brakes, designed to stop the vehicle if the service brake system fails. These three systems work together, using compressed air to provide reliable braking for large, heavy vehicles.

Why should you not fan the brakes on and off during long downgrades?

Fanning the brakes on and off during long downgrades is a dangerous practice because the short periods off the brakes do not allow them to cool down. This can lead to excessive heat buildup in the brake linings, causing brake fade or even complete brake failure. Instead, drivers should use a steady, firm application of the brakes combined with engine braking to maintain a safe speed and prevent overheating.

How do you check the free play in manual slack adjusters?

To check the free play in manual slack adjusters, first, park the vehicle on level ground and chock the wheels to prevent movement. Next, release the parking brakes. Once these steps are complete, you can pull hard on each slack adjuster you can reach to check for excessive movement. This inspection ensures the brakes are properly adjusted, which is crucial for effective braking and preventing brake fade.

What is the best way to test if your vehicle's spring brakes come on automatically?

The best way to test if your vehicle's spring brakes come on automatically is to continue stepping on and off the brake pedal. For tractor-trailer vehicles, you should do this until the parking brake valve pops out. Alternatively, you can continue this action until the manufacturer's low PSI specification has been met for the spring brakes to deploy, which is often in the range of 20 to 30 PSI. This test confirms the emergency braking system is functional.

When should you drain your air tanks?

You should drain your air tanks at the end of each working day. This daily maintenance task is crucial for preventing the buildup of water and oil within the air storage tanks. Over time, accumulated moisture and contaminants can corrode internal components, interfere with air brake valves, and potentially lead to system malfunctions or freezing in cold weather, compromising overall brake reliability.